Paragenetic sequence and zoning integrated with mineral densities for the Kupferschiefer-Zechstein section (youngest at top).
\r\n\tThis book intends to provide the reader with a comprehensive overview of the current state-of-the-art novel imaging techniques by focusing on the most important evidence-based developments in this area.
",isbn:null,printIsbn:null,pdfIsbn:null,doi:null,price:0,priceEur:0,priceUsd:0,slug:null,numberOfPages:0,isOpenForSubmission:!0,isSalesforceBook:!1,isNomenclature:!1,hash:"d9159ce31733bf78cc2a79b18c225994",bookSignature:"Dr. Gabriel Cismaru",publishedDate:null,coverURL:"https://cdn.intechopen.com/books/images_new/11867.jpg",keywords:"Hypertrophic Cardiomyopathy, Dilated Cardiomyopathy, Restrictive Cardiomyopathy, Transesophageal Echocardiography, Intracardiac Echocardiography, 3-Dimensional Echocardiography, Adult Congenital Heart Disease, Tetralogy of Fallot, Transposition of the Great Vessels, Coronary Artery Disease, Risk Stratification, Revascularization",numberOfDownloads:null,numberOfWosCitations:0,numberOfCrossrefCitations:null,numberOfDimensionsCitations:null,numberOfTotalCitations:null,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"April 21st 2022",dateEndSecondStepPublish:"May 19th 2022",dateEndThirdStepPublish:"July 18th 2022",dateEndFourthStepPublish:"October 6th 2022",dateEndFifthStepPublish:"December 5th 2022",dateConfirmationOfParticipation:null,remainingDaysToSecondStep:"3 months",secondStepPassed:!0,areRegistrationsClosed:!0,currentStepOfPublishingProcess:4,editedByType:null,kuFlag:!1,biosketch:"Dr. Cismaru Gabriel is an Assistant Professor at the University of Medicine and Pharmacy Cluj-Napoca, certified in Cardiology. After completing his certification in cardiology, Dr. Cismaru began his electrophysiology fellowship at the Institut Lorrain du Coeur et des Vaisseaux Louis Mathieu. He has authored or co-authored peer-reviewed articles and book chapters in the field of cardiac pacing, defibrillation, electrophysiological study, and catheter ablation.",coeditorOneBiosketch:"Raluca Tomoaia is an MD, Ph.D. in novel techniques in Echocardiography at the University of Medicine and Pharmacy in Cluj-Napoca, Romania., assistant professor, and a researcher in echocardiography and cardiovascular imaging.",coeditorTwoBiosketch:null,coeditorThreeBiosketch:null,coeditorFourBiosketch:null,coeditorFiveBiosketch:null,editors:[{id:"191888",title:"Dr.",name:"Gabriel",middleName:null,surname:"Cismaru",slug:"gabriel-cismaru",fullName:"Gabriel Cismaru",profilePictureURL:"https://mts.intechopen.com/storage/users/191888/images/system/191888.png",biography:"Dr. Cismaru Gabriel is an assistant professor at the Cluj-Napoca University of Medicine and Pharmacy, Romania, where he has been qualified in cardiology since 2011. He obtained his Ph.D. in medicine with a research thesis on electrophysiology and pro-arrhythmic drugs in 2016. Dr. Cismaru began his electrophysiology fellowship at the Institut Lorrain du Coeur et des Vaisseaux Louis Mathieu, France, after finishing his cardiology certification with stages in Clermont-Ferrand and Dinan, France. He began working at the Rehabilitation Hospital\\'s Electrophysiology Laboratory in Cluj-Napoca in 2011. He is an experienced operator who can implant pacemakers, CRTs, and ICDs, as well as perform catheter ablation of supraventricular and ventricular arrhythmias such as ventricular tachycardia and ventricular fibrillation. He has been qualified in pediatric cardiology since 2022, and he regularly performs device implantation and catheter ablation in children. Dr. Cismaru has authored or co-authored peer-reviewed publications and book chapters on cardiac pacing, defibrillation, electrophysiological studies, and catheter ablation.",institutionString:"Iuliu Hațieganu University of Medicine and Pharmacy",position:null,outsideEditionCount:0,totalCites:0,totalAuthoredChapters:"7",totalChapterViews:"0",totalEditedBooks:"2",institution:{name:"Iuliu Hațieganu University of Medicine and Pharmacy",institutionURL:null,country:{name:"Romania"}}}],coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"16",title:"Medicine",slug:"medicine"}],chapters:null,productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},personalPublishingAssistant:null},relatedBooks:[{type:"book",id:"5970",title:"Bedside Procedures",subtitle:null,isOpenForSubmission:!1,hash:"ba56d3036ac823a7155f40e4a02c030d",slug:"bedside-procedures",bookSignature:"Gabriel Cismaru",coverURL:"https://cdn.intechopen.com/books/images_new/5970.jpg",editedByType:"Edited by",editors:[{id:"191888",title:"Dr.",name:"Gabriel",surname:"Cismaru",slug:"gabriel-cismaru",fullName:"Gabriel Cismaru"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9064",title:"Epidemiology and Treatment of Atrial Fibrillation",subtitle:null,isOpenForSubmission:!1,hash:"1cd6bf2b3181eb82446347fbe478a2bc",slug:"epidemiology-and-treatment-of-atrial-fibrillation",bookSignature:"Gabriel Cismaru and Keith Andrew Chan",coverURL:"https://cdn.intechopen.com/books/images_new/9064.jpg",editedByType:"Edited by",editors:[{id:"191888",title:"Dr.",name:"Gabriel",surname:"Cismaru",slug:"gabriel-cismaru",fullName:"Gabriel Cismaru"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"6550",title:"Cohort Studies in Health Sciences",subtitle:null,isOpenForSubmission:!1,hash:"01df5aba4fff1a84b37a2fdafa809660",slug:"cohort-studies-in-health-sciences",bookSignature:"R. 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Each one presents a peptide-binding domain, an Ig-like domain, and a transmembrane region with a cytoplasmic tail (\nFigure 1\n). These structures are bind by non-covalent association leadings. Unlike Major Histocompatibility Complex (MHC) class I molecules, both polypeptide chains are encoded by genes in the HLA-DQ regions strictly located on chromosome 6 (\nFigure 2\n). The pocket for the bond with the peptide is constituted for half by one chain and half by the other; each one contributes with an α-helix and 4 filaments of the β sheet.
\nLabel: The structure of the MHC-II molecule [
Label: Chromosomal origin of HLA class I and class II [
In the extracellular portion, each chain has an Ig domain (α2 and β2) of which, β2 contains the binding site for lymphocyte helper CD4+. In HLA-DQ2 both the α-chains and the β-chains are polymorphic, as a result, unique DQ molecules can be formed, with α- and β-chains encoded on the same chromosome (encoded in cis) or on opposite chromosomes (encoded in trans). However, evidence suggests that not every α- and β-chain pairing will form a stable heterodimer. It is generally considered that alleles of DQα- and DQβ-chains pair up predominantly in cis rather than in trans. However, the occurrence of trans-encoded HLA class II molecules is well documented in the literature, such as in the case of type 1 diabetes (T1D), where the trans encoded HLA molecules may play a role in pathogenesis [4].
\nEach MHC molecule has only one antigen pocket that can bind one peptide at once, but different peptides at different times. Peptides that can bind to MHC-II molecules reach 30 or more, while class I MHC molecules can accommodate peptides with 8–11 amino acids. The peptide–MHC binding is created during its assembly and is used to stabilize the complex to allow its expression on the cell surface and for this reason, the dissociation rate is very slow. This naturally provides a very long half-life that allows T lymphocytes to meet the antigen. Between MHC and peptide, a non-covalent connection is formed among the residues in the pocket. Once the binding has occurred, the peptide and the water molecules that solubilize it fill the pocket, making contact with the walls and the floor that make it up.
\nT cells activated by class II molecules are CD4+ helper cells that: activate cytokine production, control antibody synthesis, and regulate cellular response. DQ is also involved in the common recognition of auto-antigens; the presentation of these antigens to the immune system provides tolerance at a young age. When this tolerance is lost DQ can be involved in autoimmune diseases such as celiac disease (CD), type 1 diabetes, and many others as we will see more details afterward [5].
\nAs mentioned before, there are many potential DQ isoforms, as a result of the combination of cis- and trans haplotypes and those with cis-pairing are more common. Typically individuals can produce 4 isoforms, but only HLA-DQ2.5 and HLA-DQ2.2 tend to be predominantly represented.
\nHLA-DQ2.5 is composed of the allele HLA-DQA1*0501 (or DQA1*0505) encoding the alpha chain and the allele HLA-DQB1*0201 (or DQB1*0202) encoding the beta chain. HLA-DQ2.2 consists of the HLA-DQA1*02 alpha chain allele and the HLA-DQB1*0202 beta chain allele [6].
\nVery important concerning isoforms is that different subunit matches can cause the binding of different foreign or self-antigens. Generally, MHC molecules have slots at the pocket level that can interact with specific amino acids or be complementary to certain amino acid side chains. The importance of polymorphism is detected here: only the ability of MHC to bind specifically to a peptide permits it to be recognized by lymphocytes and to trigger the immune response to it.
\nThe molecule HLA-DQ2 has a peculiar ligation system with three binding sites, preferably for negatively charged residues and different peptide-binding motifs. The binding motifs associated with HLA-DQ2 consist of truncated variants of eight different peptides with a length of 9–19 amino acids.
\nData from the pooled sequencing and the biochemical binding analyses of synthetic variants of a ligand indicate that the side chains of amino acid residues at relative position P1 (bulky hydrophobic), P4 (negatively charged or aliphatic), P6 (Pro or negatively charged), P7 (negatively charged) and P9 (bulky hydrophobic) are important for binding of peptides to DQ2 (\nFigure 3\n).
\nLabel: Analysis of the HLA-DQ2 protein: (A) the 3D structure; (B) the binding sites; (C) the amino acids residues and the α helix and the β sheet domains [
Computer modeling of the DQ2 with variants of the ligand in the groove suggests that peptides bind to DQ2 through the primary anchors P1, P7, and P9 and making additional advantageous interactions using the P4 and P6 positions [8].
\nDQ2.5 refers to both a protein isoform and a genetic haplotype. DQ2.5 isoform or heterodimer is shorthand for the cell surface receptor HLA-DQ α5β2 (\nFigure 4\n).
\nLabel: The crystal structure of HLA-DQ2.5-CLIP1 [
DQ2.5 and the linked DR3 are associated with probably the greatest frequency of autoimmune occurrence relative to any other haplotypes. A genome-wide survey of markers linked to celiac disease, reveals that the highest linkage is for a marker within the DQA1*0501 allele of the DQ2.5 haplotype. The association of DQB1*0201 is almost as high. Greatly elevating risk is the ability of the DQ2.5 haplotype encoded isoforms to increase abundance on the cell surface in DQ2.5 double homozygote. While the frequency of DQ2.5 haplotype is only 4 times higher than the general population, the number of DQ2.5 homozygotes is 10 to 20 times higher than the general population. Of the approximately 90% of celiacs that bear the DQ2.5 isoform, only 4% produce DQ2.5trans and differs slightly, one amino acid, from DQ2.5cis.
\nMultiple copies of the DQ2.5 haplotype do not cause apparent increases of severity in celiac disease, but the 25% of celiac patients homozygous DQ2 (DQ2.5/DQ2) tend to show increases risk of life-threatening complications and more severe histological findings. The HLA-DQ2.5 molecule preferentially binds peptides with negatively charged amino acids at anchor positions [10, 11]. Whereas gluten peptides contain few negative charges, these charges can be introduced by the enzyme tissue transglutaminase (tTG) that selectively deamidates glutamine residues in gluten peptides [12, 13, 14]. DQ2.5cis is the major factor in adaptive immunity by frequency and efficiency in alpha-gliadin presentation and its responses can be differentiated from other DQ isoforms. Specifically, this DQ2 heterodimer is responsible for presenting the α2-gliadin that most effectively stimulates pathogenic T-cells.
\nAs mentioned before, the DQ2.5 haplotype is linked to DR3, which is not linked to DQ2.2. Using either serotyping or genotyping DQ2.5 can be distinguished from DQ2.2 or DQ2.3 [5].
\nHLA-DQ2.2 is shorthand for the DQ α2β2 heterodimeric isoform (\nFigure 5\n). DQ2.2 homozygotes represent about 1.1% of the celiac population. While HLA-DQ2.5 is strongly associated with the disease, HLA-DQ2.2 is not [5].
\nLabel: The crystal structure of HLA-DQ2.2 [
Whereas the molecular surfaces of the antigen-binding clefts of HLA-DQ2.5 and HLA-DQ2.2 are very similar, there are important differences in the nature of the peptides presented. These peculiarities in peptide motif binding cause differences in responding to T cell repertoires and in the disease penetrance [16].
\nDQ2.2 individuals can mount an antigluten response but bear a lower risk of celiac disease. The reason is fewer gluten peptides would bind stably to this HLA molecule. The results give insight into processes important for the establishment of T-cell responses to antigen in HLA-associated diseases. Patients with celiac disease with DQ2.2 have gluten-reactive T cells in their small intestine [17].
\nDQ2.3 is the shorthand for the heterodimeric DQ α3β2 isoform and is encoded by the DQA1*03:DQB1*02 haplotype (\nFigure 6\n). The receptor coded for the haplotype is a DQ2.3cis isoform, which is genetically linked to DR7 [5]. The gluten epitope, which is the only known HLA-DQ2.3-restricted epitope, is preferentially recognized in the context of the DQ2.3 molecule by the T-cell clones of a DQ8/DQ2.5 heterozygous celiac patient.
\nLabel: The crystal structure of HLA-DQ2.3 [
The DQ2.3 molecule combines the peptide binding signatures of the DQ2.5 and DQ8 molecules. This results in a binding motif with a preference for negatively charged anchor residues at both the P1 and the P4 positions. In this way, some epitopes can be presented even more effectively in the context of the trans-encoded DQ2.3 molecule. This has relevance for understanding how the trans-encoded DQ2.3 molecule is predisposing to type 1 diabetes [4].
\nThe analysis of the structure of DQ2.3 together with all other available DQ crystals shows that the P1 pocket in DQ2.3 is significantly different from that of DQ2.5 due to the polymorphic MHC residues found in this region. Additionally, DQ2.3 presents a gluten epitope to T-cells much more efficiently than DQ2.5 [4].
\nDQ2 beta chains can combine with trans chains to other alpha chains. However, there is no preference in cis isoforms for DQ2 alpha chains, 4, 7, 8, or 9 bindings to DQ1 alpha chains (DQA1*01). The DQA1*03, *05 chains process nearly identical alpha chains. The *04 chain can potentially combine with DQ2 to form DQ2.4. There is the possibility of DQ2.6 resulting from coupling with DQA1*0601 [5].
\nCeliac disease is a genetically determined immune-mediated disorder in which individuals carrying HLA DQ2 and/or DQ8 haplotypes develop an immunologic response to gluten ingestion that leads to a wide range of clinical signs and symptoms.
\nThe Humoral nature, the hereditary and the polygenic CD have great influence in triggering the disease. The assessment of HLA-DQ2/DQ8 is relevant from a diagnostic aspect to detect celiac disease; in fact, about 95% of patients with CD present the HLA-DQ2 genotype [19].
\nIn celiac patient inflammatory T cell responses to HLA-DQ2-bound gluten peptides are thought to cause disease. Gluten-reactive T cells can be isolated from small intestinal biopsies of celiac patients. T cells derived from the lesion mainly recognize gluten deamidate peptides. There are several distinct T cell epitopes within gluten. DQ2 and DQ8 bind the epitopes so that the glutamic acid residues created by deamidification are placed in compartments that have a preference for negatively charged side chains. Evidence indicates that in vivo deamidation is mediated by the enzyme tissue transglutaminase (tTG) that can also cross-link glutamine residues of peptides with lysine residues in other proteins, including tTG itself. This can lead to the formation of gluten-tTG complexes. These complexes may allow gluten-reactive T-cells to provide aid to tTG-specific B-cells through an intramolecular aid mechanism, thus explaining the presence of gluten-dependent tTG autoantibodies which is a characteristic feature of active CDs.
\nIdeally, all patients with CD carry alleles encoding for the DQ2 and/or DQ8 molecules or at least one chain of the DQ2 heterodimer. The presence of CD in the absence of these DQ risk factors is extremely rare. The presence of these molecules does not accurately predict that CD will develop, as they are present in 25–50% of the general population, although the fact that the vast majority of these individuals will never develop the disease. About 90% of individuals with CD carry HLA-DQ2.5, while individuals with CD who do not express these haplotype usually express either HLA-DQ2.2 or HLA-DQ8; very few coding for HLA DQ7.5 (DQA1*05:05–DQB1*03:01), DQ2.3 or DQ8.5 (DQA1*05–DQB1*03:02).
\nDifferences in CD risk between haplotypes are related to gluten peptide binding and subsequent T-cell response. The effect of gene dose is related to the level of peptide binding to homozygous and heterozygous HLA-DQ2 and its subsequent presentation to T cells. Individuals homozygous for DQ2.5 and DQ8 have an increased risk of the disease. Gluten presentation by HLA-DQ2 homozygous was superior to HLA-DQ2/non-DQ2 in terms of T cell proliferation and cytokine secretion (\nFigure 7\n).
\nLabel: Haplotypes and different class risk for celiac disease [
HLA-DQ2.5 predisposes to celiac disease respect to DQ2.2, because the first one presents a large repertoire of gluten peptides, whereas the second one presents only a subset of these. HLA-DQ2.2 does not predispose to CD unless it is expressed in combination with HLA-DQ2.5. Gluten presentation by HLA-DQ2.5/2.2 induces intermediate T-cell stimulation. However, individuals homozygous for HLA-DQ2.5 or heterozygous HLA-DQ2.2/2.5 have the highest risk of developing CD. In HLA-DQ2.5/2.2 heterozygous individuals have properties identical with HLA-DQ2.5 dimers. In contrast, HLA-DQ2.5/non-DQ2.2 heterozygous individuals have an only slightly increased risk (\nFigure 8\n).
\nLabel: Genotypes and celiac disease prevalence [
Considering even more in detail, it has been demonstrated that differences in conferred risk associated with CD are the result of the polymorphism in the α chain between HLA-DQ2.5 and HLA-DQ2.2.
\nHLA-DQ2.2 is virtually identical to the peptide-binding properties of HLA-DQ2.5. Both are highly homologous except for a single polymorphic residue (HLA-DQ2.5-Tyr22α and HLA-DQ2.2-Phe22α). The role of the Phe22α variant in HLA-DQ2.2 is to influence peptide binding preferences and to decide how DQ2.2 TCRs engage the DQ2.2-gluten complex.
\nCrystal structure studies revealed a docking strategy, where the TCR HLA-DQ2.5 gliadin epitopes complexes were notably distinct from the HLA-DQ2.2-glut TCR complex [22].
\nHLA-DQ2.5 and HLA-DQ2.2 binds and presents gluten peptides with glutamate residues at anchor positions P4, P6, or P7). Three HLA-DQ2.2 epitopes (DQ2.2-glut-L1, DQ2.2-glia-α1, and DQ2.2-glia-α2) have sequences similar to HLADQ2.5 binding peptides, with the exception that they all carry serine at P3. As seen for HLA-DQ2.5 epitopes, the HLA-DQ2.2 ones display a hierarchy with DQ2.2-glut-L1 being the epitopes recognized by most T cells [23].
\nHLA-DQ2 is influenced by interaction with Ag presentation cofactors, invariant chain (Ii), HLA-DM (DM), a peptide exchange catalyst for MHC class II (\nFigure 9\n).
\nLabel: Localization of HLA-DM on the MHC class II region [
DM can enhance or suppress the presentation of specific MHCII peptide complexes. In general, MHCII–peptide complexes with lower intrinsic stability are DM susceptible, but not all high-stability complexes are DM resistant. HLA-DQ2 is relatively resistant to DM because DQ2 has a natural deletion in the region involved in the interaction with DM, compared with most other alleles.
\nThe role of DQ2/DM concerns interaction in the DQ2-restricted gliadin epitopes, relevant to celiac disease, or DQ2-restricted viral epitopes, relevant to host defense. DM activity has different consequences on DQ2 presentation of epitopes to T cell clones, with suppression of gliadin presentation and enhancement of viral peptide presentation. These results imply key differences in DQ2 Ag presentation pathways.
\nDM-resistant feature of DQ2 likely contributes to the escape of gliadin peptides from extensive DM editing. Also, DQ2 has the special ability to stably bind proline-rich gliadin peptides that use TG2-deamidated residues as DQ2-binding anchors. Together, these unique features of DQ2 may allow gliadin presentation to disease-driving CD4+ T cells and contribute to the uniquely selective DQ2 presentation of DM-sensitive gliadin epitopes.
\nIn contrast, the presentation of DM-resistant epitopes that form more-stable complexes with DQ2 likely relies less on the above mechanisms, as DM editing positively affects the presentation of these epitopes. The elevation of DM expression in peripheral APC (particularly during infection) may benefit self-tolerance by attenuating the presentation of DM-sensitive epitopes while boosting the presentation of DM-resistant pathogen-derived epitopes and aiding in host defense [25].
\nRefractory celiac disease (RCD) is defined by persistent mal-absorptive symptoms and villous atrophy despite strict adherence to a GFD for at least 6–12 months in the absence of other causes of non-responsive treated celiac disease.
\nThe pathology can be classified as type 1 (normal intraepithelial lymphocyte phenotype), or type 2 (defined by the presence of abnormal [clonal] intraepithelial lymphocyte phenotype). RCD 1 usually improves after treatment with a combination of aggressive nutritional support, adherence to GFD, and alternative pharmacologic therapies. By contrast, clinical response to alternative therapies in RCD 2 is less certain and the prognosis is poor. Severe complications such as ulcerative jejunity and Enteropathy T-cell lymphoma (ETL) may occur in a subgroup of patients with RCD [26].
\nETL is a T-cell non-Hodgkin lymphoma arising in the gastrointestinal tract that shows a differentiation of tumor cells toward the phenotype of intestinal intraepithelial T cells. The clinical course of ETL is highly aggressive, with most patients dying from the disease within months of diagnosis. Enteropathy T-cell lymphoma comprises two morphologically, clinically, and genetically distinct lymphoma entities: the ETL type 1 and 2.
\nETL arises in individuals with the DQA1*0501, DQB1*02 CD-predisposing genotype. The HLA typing found in these patients revealed that more than 95% have an HLA-DQ2/-DQ8 genotype [27]. Comparing studies of HLA-DQB1 genotyping in celiac disease and ETL have detected that the overall HLA-DQB1 genotype pattern observed in type 1 ETL closely resembled those for ETL, whereas those of type 2 ETL are not significantly different from that of normal Caucasian controls.
\nETL1 patients show significantly more frequent expression of HLA-DQB1*02 than the type 2 ones [28]. Lymphoma type 1 may arise and be pathogenetically linked to refractory celiac disease by a stepwise acquisition of genetic alterations. Contrary given the genetic alterations and HLA-DQB1 genotype patterns, celiac disease may not be causal to type 2 ETL. At least 47% of patients with type 2 ETL are very likely to never have had celiac disease [29].
\nThe highly significant correlation between HLA-DQ2 homozygosity and the development of RCD II and ETL, suggests that the strength of the gluten-specific T-cell response in the laminapropria directly or indirectly influences the likelihood of RCD II and lymphoma development. As already mentioned in the chapter, also in this case, the higher T-cell proliferation and cytokine secretion induced by HLA-DQ2 homozygous APC, than HLA-DQ2 heterozygous APC, may explain the strongly increased risk for disease development in HLA-DQ2/DQ2 individuals [30]. This would indicate that adherence to a gluten-free diet is particularly important for CD patients who are HLA-DQ2 homozygous.
\nThese observations suggest that specific tests, such as those for lymphocyte typing for T cells, should be indicated in all patients with CD who are not responding to a gluten-free diet. The availability of a simple and reliable immune histochemical method can make the distinction between CD and RCD feasible. HLA-DQ typing is doable and it may be an efficient test to recognize individuals at risk for these conditions with a poor prognosis, particularly now that some evidence has been given to support the hypothesis that autologous hematopoietic stem-cell transplantation can alter disease progression in severe [29].
\nLiver and gastrointestinal diseases have many etiologies that are poorly understood. Whether due to genetic abnormalities, psychological factors, or other environmental variables, functional disorders can be complex and difficult cases to resolve. A strongest evidence of an association with
Known immunological associations between IBD and DR7, which is linked to both DQ2 and DQ8 haplotype have been established. The relation between DQ2/8 and IBD/IBS was analyzed in particular in two studies from an Italian and a Danish group and both demonstrated that the proportion of IBS was lower among HLA DQ2/8 positive individuals. However the Italian group also found that IBD and liver diseases were more prevalent among HLADQ2/8 subjects, but it is not confirmed in the Danish study. Prior prevalence data though suggest that IBD, particularly Crohn’s disease, is lower in individuals with the DQ2/8 linked celiac disease.
\nIBS has also been linked to HLA DQ2/8 haplotypes and intestinal transit rates [31]. Approximately 46% of patients with diarrhea-predominant IBS (IBS-D) have accelerated colonic transit. Some patients with IBS report an association of symptoms with specific foods, suggesting a role for food hypersensitivity. One such food is gluten in the absence of overt celiac disease. The spectrum of gluten sensitivity ranges from minimal histological changes such as increased intraepithelial lymphocytes without villous atrophy, increased immunoglobulin A (IgA) deposits in intestinal villi, gluten-sensitive diarrhea, and immunological mucosal response to gluten exclusion in patients with celiac disease. Typically, one or more of these findings are seen in individuals who are positive for HLA-DQ2 or HLA-DQ8. Wahnschaffe et al. demonstrated that, among patients with IBS-D, response of diarrhea to a gluten-free diet was influenced by HLA-DQ2 positivity and the presence of IgG tissue transglutaminase (TTG) antibody in duodenal aspirates. Symptom response to gluten withdrawal occurred in 62% of patients positive for both HLA-DQ2 and IgG-TTG; in contrast, only 12% of patients negative for HLA-DQ2 and TTG-IgG responded; suggesting that symptom generation in this subset of patients is immune-mediated. Is demonstrated that patients with IBS-D, positive for either HLA-DQ8 or both HLA-DQ2/DQ8 genotypes that are associated with gluten sensitivity, have an accelerated colonic transit time [32].
\nThe HLA DQ2 in association with HLA-DR3 is also associated with another GI disease; in fact, this combination is linked with a more rapid progression of primary sclerosing cholangitis (PSC) [33].
\nType 1 diabetes (T1D) is an autoimmune disease attacking pancreatic Langerhans islets. The islets are composed of several types of cells: α, β, δ, ε, and pancreatic polypeptide (PP). Each type plays a different role in the secretory function of the pancreas and, among others, α and β cells produce glucagon and insulin, respectively. The interplay between these two compounds provides proper glucose level administration in blood.
\nIt has been already shown that auto aggression in T1D starts in mutations in the MHC system. HLA-DQ molecules have the role to bind and present beta-cell autoantigen derived peptides in T1D. The combinations of DR4-DQ8 and DR3-DQ2 antigens occur in 90% of people with diabetes. However, the homozygous state for an allele does not further increase the risk. Indeed it is well established that individuals heterozygous for HLA-DQ2 and HLA-DQ8 have almost 5 fold higher risk than homozygous to development of T1D [1, 13, 14]. This has been linked to the formation of trans dimers between the HLA-DQ2 α chain and the HLA-DQ8 β chain (HLA-DQ8 trans) [19, 22, 26, 34]. In particular, the HLA DQ8 trans heterodimer confers the highest risk for the development of T1D. This indicates that such HLA-DQ trans dimers can bind and present a unique autoantigen derived peptide that leads to beta-cell destruction in the pancreas and the development of T1D [35].
\nJuvenile diabetes has a high association with DQ2.5. A combination of DQ2.5 and DQ8 significantly increases the risk of type 1 onset of adult diabetes, while the presence of DQ2 with DR3 reduces the age of onset and severity of the autoimmune disease.
\nThe formation of trans encoded molecules DQ8.5 (DQA1*05:01/DQB1*03:02) and DQ2.3 (DQA1*03:01/DQB1*02:01), which could present one or a few specific diabetogenic epitopes to CD4+ T-cells, possibly inducing an immune response that leads to the destruction of insulin-producing pancreatic β islet cells [12]. A strong argument for the involvement of the DQ2.3 heterodimer in type 1 diabetes comes from trans racial gene mapping studies that have found that this heterodimer, which is typically found in the trans configuration among Caucasian subjects, exists and is over-represented in the cis configuration among type 1 diabetes patients of African origin [16, 17]. The increased diabetes risk of the African DQ2.3 (DQA1*03:01/DQB1*02) carrying DR7 haplotype is contrasted by a protecting effect of the DQ2.2 (DQA1*03:01/DQB1*02) carrying DR7 haplotype of European origin [17].
\nPatients with homozygous type 1 DQ2 diabetes have a marked prevalence of IgA anti-transglutaminase autoantibodies. The great excess of positive transglutaminase autoantibodies among homozygous DQ2 diabetics is related to both the presence of DQ2 and its addition to all genetic or environmental factors associated with type 1 diabetes. These additional factors may be related to abnormalities in mucosal immunity that increases the risk of both type 1 diabetes and celiac disease.
\nType 1 diabetes is an autoimmune disease attacking pancreatic Langerhan’s islet. The islet is composed of several types of cells: α, β, δ, ε, and pancreatic polypeptide (PP). Each type plays a different role in the secretory function of the pancreas and, among others, α and β cells produce glucagon ad insulin, respectively [36]. Interplay between these two compounds provides proper glucose level administration in blood.
\nIt has been already shown that auto aggression in T1D starts in mutation in the MHC system. HLA-DQ molecules have the role to bind and present beta cell autoantigens derived peptides in T1D. The combinations of DR4-DQ8 and DR3-DQ2 antigens occur in 90% of people with diabetes. However, the homozygous state for an allele does not further increase the risk. It is well established that individuals heterozygous for HLA-DQ2 and HLA-DQ8 have an almost 5 fold higher risk than those who are homozygous for either of the DQ variants for the development of T1D, and this has been linked to the formation of trans dimers between the HLA-DQ2 α chain and the HLA-DQ8 β chain (HLA-DQ8 trans). This indicates that such HLA-DQ trans dimers can bind and present a unique auto antigen-derived peptide that leads to beta-cell destruction in the pancreas and the development of T1D. In particular, HLA DQ8 trans heterodimer confers the highest risk for the development of T1D.
\nIndeed diabetes has a high association with DQ2.5. A combination of DQ 2.5 and DQ8 significantly increases the risk of type 1 onset of adult diabetes, while the presence of DQ2 with DR3 reduces the age of onset and severity of the autoimmune disease.
\nThe formation of trans encoded molecules DQ8.5 (DQA1*05:01/ DQB1*03:02) and DQ2.3 (DQA1*03:01/DQB1*02:01), which could present one or a few specific diabetogenic epitopes to CD4+ T cells, possibly inducing an immune response that leads to the destruction of insulin-producing pancreatic β islet cells. Moreover, a strong argument for the involvement of DQ2.3 heterodimer in type 1 diabetes comes from transracial gene mapping studies that have found that this heterodimer, which is typically found in the trans-configuration among Caucasian subject, exists and is over-represented in the cis configuration among type 1 diabetes patients of African origin. The increased diabetes risk of the Africans DQ2.3 carrying DR7 haplotype is contrasted by a protecting effect of the DQ2.2 carrying DR7 haplotype of European origin, speaking to the functional importance of α chain in the DQ2.3 molecule.
\nPatients with homozygous type 1 DQ2 diabetes have a marked prevalence of IgA anti-transglutaminase autoantibodies. The great excess of positive transglutaminase autoantibodies among homozygous DQ2 diabetics is related to both the presence of DQ2 and its addition to all genetic or environmental factors associated with type 1 diabetes. These additional factors may be related to abnormalities in mucosal immunity that increases the risk of both type 1 diabetes and celiac disease. In T1D the risk associates with the HLA-DQ2/8 heterozygous haplotype was found to be increased compared with homozygous HLA-DQ2 or HLA-DQ8 individuals, suggesting an epistatic or synergic effect [37].
\nThe term autoimmune thyroid disease (AITDs) encompasses several different entities characterized by varying degrees of thyroid dysfunction and the presence of serum auto-antibodies against thyroid tissue-specific components, such as thyroglobulin (TG) and thyroid peroxidase (TPO) [34].
\nHashimoto’s thyroiditis (HT) and Graves’ disease (GD) are AITDs with different physiopathology, being traditionally regarded as two different disease entities. More recent views, in contrast, have considered the hypothesis that there might be a continuum between HT and GD.
\nGenes of, or closely associated with, the HLA complex are assumed to contribute to the genetic predisposition to AITDs. Genetics plays a prominent role in both the determination of thyroid hormone and thyrotropin (TSH) concentrations and susceptibility to autoimmune thyroid disease. Heritability studies have suggested that up to 67% of circulating thyroid hormone and TSH concentrations are genetically determined, suggesting a genetic basis for narrow intra-individual variation in levels [34]. Until today the mechanisms leading to thyroid autoimmunity are largely unknown.
\nIn 30%–40% of healthy individuals, DQ2, and DQ8 are associated with diseases such as Hashimoto’s Thyroiditis. In patients with a CD instead, autoimmune thyroid disease was observed in 14% and 30.3% in adults, while thyroid abnormalities were described in 37.6% and 41.1% in pediatric age.
\nNoteworthy was the presence of high titers of serum TPO antibodies [11] and serum TG antibodies [12] in the celiac pediatric patients without a gluten-free diet (GFD), these values were reported to return to normal after 2 or 3 years on a GFD. This finding suggests that these antibodies are gluten dependent.
\nFurthermore has been analyzed the association between Hashimoto’s thyroiditis and celiac disease in the Dutch population and it has been demonstrated that HLA DQ2.5 was associated with higher TSH levels. This correlation is not been found for the other thyroid markers (TPO, FT4). A reason could be that TSH is a more sensitive marker for hypothyroidism, as well as the fact that TSH is a quantitative parameter measured in all participants of that study, giving more power to detect differences.
\nMore than doubled GD rates are correlated to the genetic association to the DR3-DQ2 haplotype [38]. A study of Asian Indian patients with Graves’ disease revealed a significant increase in the frequency of HLA-DQW2 as compared to the control population [37]. HLA-DQA1*0501 was also shown to be associated with GD in a Caucasian family study [37] but, the primary susceptibility allele in GD is indeed HLA-DR3 [37]. Further analyses have shown that these variants are almost always inherited together in Caucasian populations, so they act as a single genetic factor. These haplotypes are among the crucial genetic factors of celiac disease in European descendants, confirming a strong connection between gluten intolerance and autoimmune thyroid conditions. This theory is confirmed by studies on a large UK Caucasian case–control population, which have shown that the contribution of the HLA class II region to the genetic susceptibility of Graves’ disease is due to the haplotype DRB1*0304-DQB1*02-DQA1*0501, with no independent association of any individual allele. However, as a result of strong linkage disequilibrium within the MHC region, it is difficult to assess which loci are acting as primary etiological determinants. The same HLA haplotype is associated with the large multifunctional proteasome 2 loci (LMP-2). The LMP molecules are overexpressed in thyrocytes, the target cells of Graves’ disease and the LMP genes are found within the MHC class II region. The LMP genes may therefore play a role in susceptibility to Graves’ disease [39].
\nDermatitis herpetiformis (DH) is a chronic, pruritic, papulovesicular skin disease of unknown origin. The characteristic rash is symmetrically distributed over the extensor surfaces and buttocks and, also, most patients with DH have asymptomatic gluten-sensitive Enteropathy [40].
\nAll patients with DH had typical clinical and histologic features, as well as granular deposits of IgA at the dermal-epidermal junction. The gastrointestinal lesions are essentially identical to those seen in patients with ordinary CD, although less severe and more patchy. A pathophysiologic link between CD and DH has been suggested by the observation that the skin lesions of DH as well as the abnormalities of the jejunal mucosa regress on a gluten-free diet.
\nDH is associated with a markedly increased frequency of the HLA class II antigens DR3 and DQ2. The primary HLA association is HLA-DQ2 (expressed in 100% of DH patients), whereas the HLA-DR3 is code in 95% of cases [41]. HLA-DQ8 may therefore be a second HLA susceptibility molecule in DH; all the DH patients carrying DQ2 plus a DR4 haplotype also carried DQ8.
\nAn increased frequency of DR3, DQ2 homozygosity, and a slightly increased frequency of DR3, DQ2 heterozygosity were found among the DH patients. It is, therefore, possible that a gene dosage effect of DQB1*02 may be present also in DH patients.
\nDH and CD both are primarily associated with the same DQ (α1*0501, β1*02) heterodimers, and in both diseases most of the few remaining patients not carrying this heterodimer instead carry the DQ (α1*03, β1*0302) heterodimers.
\nIn patients where a jejunal biopsy has been performed have been detected abnormal biopsies both among the DQ (α1*0501, β1*02) positive and negative patients. No significant differences in the frequency of abnormal biopsies were observed between the two groups of patients.
\nCD and DH have different HLA associations; CD being primarily associated with genes in the DQ/DR region, while DH was more strongly associated with genes in the complement region. Anyway, the very similar associations in CD and DH to the same cis or trans associated DQ2 heterodimer, or the DQ8 heterodimer, can be taken as an argument against differences in primary HLA associations in these two diseases [41].
\nRecurrent pregnancy loss (RPL) is diagnosed when three or more consecutive spontaneous abortions occur. RPL occurs in about 2–3% of clinically diagnosed pregnancies of reproductive-aged women.
\nAt present, accepted etiologies for RPL include parental chromosomal abnormalities, untreated hypothyroidism, uncontrolled diabetes mellitus, certain uterine anatomic abnormalities, antiphospholipid antibody syndrome, thrombophilias, infections, and environmental factors [42].
\nIn RPL women, an increased risk of immune abnormalities, such as increased antinuclear antibodies (ANA) and thyroid antibody is been observed [43].
\nHowever, in 40% of cases, the cause is unknown.
\nA significant association between RPL and celiac disease is been demonstrated. Various pathogenic mechanisms underlying the pregnancy failure in CD have been suggested: among them the ability of anti-transglutaminase antibodies to impair the trophoblast invasiveness and endometrial endothelial cells differentiation and disrupt early placentation. A higher proportion of individuals HLA DQ2/DQ8 positive in women with RPL compared to controls is found, (52.6% vs. 23.6%), with 3.6 times higher odds of DQ2/DQ8 positivity.
\nWhether a similar mechanism to that of CD can be linked to this obstetric complication needs to be investigated. This model might appear a simplification of all the complex mechanisms underlying RPL.
\nThe HLA-DQ2/DQ8 alleles by themselves, outside of CD, are found more frequently in RPL women. A possible pathogenic link of HLA-DQ2/DQ8 positivity, in presence of exogenous still unknown stimuli, may favor an immune condition with detrimental effects during the early stages of pregnancy.
\nA statistically significant association between HLA-DQ2/DQ8 and ANA positivity in RPL women is demonstrated. There is a significantly higher prevalence of ANA positivity in RPL women compared to control (~ 50% vs. 8.3%–27%).
\nANA are a group of autoantibodies found both in the serum of patients with autoimmune and rheumatic diseases and in the general population.
\nAs serological markers, ANA show diagnostic and prognostic significance, while their clinical utility in normal individuals is still unclear. Even if many serologically positive individuals will never develop an autoimmune disease, others may be in a pre-autoimmune state.
\nFurther studies are needed to better understand the possible pathogenic mechanism to this observation; the clinical and therapeutic implications of our observation to provide a new approach to RPL couples [44].
\nHLA class-II alleles are associated with some allergies indicating that these alleles might confer susceptibility to the respective allergens. HLA plays a role in antigen/allergen presentation and IgE deregulations.
\nFew studies have associated HLA DQ2/DQ8 with allergy and other ones have analyzed the association between HLA class II antigens and the specific IgE response to purified allergens. One of these studies found an association between DQ8 and have in specific IgE immune response in individuals with a latex allergy, while others found DQ2 to be associated with olive pollen. However, the association of HLA DQ2/8 with allergy remains unclear.
\nThere is a significant difference between HLA DQ2/8-positive and -negative individuals for dust mite allergy.
\nA significant association between the IgE antibody response to a highly purified allergen from olive tree pollen and HLA class II antigens DR7 and DQ2 in Spanish patients with seasonal allergic pollenosis is reported. The HLA-DQ2 phenotypic frequency is greater in patients with IgE antibodies olive tree pollen compared with the control group.
\nThe combined involvement of DR and DQ in the allergen response has only been described in the study of reactive T-cell repertoire in a mite sensitized patient. It’s identified HLA-DR and DQ restricted T-cell epitopes, one of which can bind to both DR and DQ molecules.
\nThese results empathize the importance of genetic factors in the allergic response. As described in several reports, antigen-specific and non-specific factors are involved in genetic restriction.
\nUntil now none of these factors can be considered as the exclusive determinant of the restriction. It is necessary to perform more studies with T-cell lines and peptides of this protein to determine which is the main region implicated in this response, and clarify this complex response [45].
\nInfection with human immunodeficiency virus type 1 (HIV-1) and progression to acquired immune deficiency syndrome (AIDS) are controlled by both host genetic factors and viral factors.
\nThe HLA region controls immune response functions and tissue rejection and influences susceptibility to infectious diseases including HIV. There are HLA class II alleles associated with susceptibility to and protection from HIV-1 infection and that these differences between ethnic groups.
\nIn the HIV+ Caucasian group, a poor prognosis was associated with HLA-DQ2 and a preferable prognosis was associated with HLA-DQ3.
\nThe HLA-DQ3 association appears to be linked with the development of Toxoplasmic Encephalitis (TE) in AIDS. An association of HLA-DQ2 with the occurrence of opportunistic infections in AIDS patients is been confirmed [46]. Of interest was the absence of difference in the frequencies of the HLA-DQ2 antigen between TE patients and controls.
\nThe development of TE in HIV infected patients is regulated by genes in or near the HLA complex and suggests that HLA-DQ typing may help in decisions regarding TE prophylaxis.
\nAn immune response gene in the DQ region may control the progression of HIV infection in adults. The rapidly progressive DQ-associated peptide might block the progression of HIV if given as a novel vaccine [47].
\nAlthough DQ2 is associated with vigorous antigluten T cell responses, DQ2 also is associated with poor responses to several vaccines and failure to control hepatitis virus C and hepatitis virus B.
\nStudies analyses the association between HLA class II alleles and haplotypes with antibody response to recombinant HBsAg vaccination in Iranian healthy adult individuals. The results, in parallel with other reports, confirm the association of certain HLA class-II alleles with a lack of antibody response to HBsAg vaccine [48].
\nDiscordant HLA/peptide binding and cytokine production patterns observed in genetically identical monozygotic twins vaccinated with HBsAg suggest the involvement of post genetic and environmental factors influencing the T cell repertoire.
\nHowever, APC from non-responders can present HBsAg to HLA class II-matched T-cells of responders. This indicates that defective HBsAg-specific T-cell repertoire rather than APC dysfunction could be involved in vaccination failure [49].
\nSeveral studies have established significant associations between DQ2, primary sclerosing cholangitis, and hepatitis C virus recurrence after transplant. A significant relationship between the individual scores of HLA mismatches HLA-DQ2 and the recurrence of HCV was observed.
\nThe large proportion of DQ2/8 positive viral hepatitis patients agrees with the hypothesis that these haplotypes may be involved in certain liver disease pathogenesis. DR3-DQ2 haplotype is the principal risk factor for the disease [50].
\nAnalyses by restriction fragment length polymorphism do not implicate a single susceptibility gene at the DQ locus. The unique factor that allows patients with autoimmune hepatitis to be distinguished from normal subjects or those with viral hepatitis is the DR3-DQ2 haplotype.
\nThe association of DQ2 with suboptimal responses to some viruses raised the possibility that its reduced interaction with DM might also lead to the presentation of moderate-affinity viral peptides, whose unstable binding to DQ2 would reduce the surface of the DQ2/peptide complex and compromise CD4+ T cell responses [51].
\nHLA genes also play a role in reproduction, pregnancy maintenance, in parental recognition and have been associated with over 100 diseases and disorders including autism.
\nAutism remained a poorly understood pathology for several decades. It is important to note that the diagnostic criteria have been modified over the years to include a broader category of symptoms, thus increasing the number of children diagnosed with the disorder, now referred to as Autism Spectrum Disorder (ASD) [52].
\nIt has been reported that ASD subjects often have associations with HLA genes or haplotypes, suggesting underlying deregulation of the immune system mediated by HLA genes.
\nA significant number of autistic children have serum levels of IgA antibodies against the enzyme tissue transglutaminase II (TG2) above normal, and the expression of these antibodies is linked to the HLA-DR3, DQ2, and DR7, DQ2 haplotypes [53].
\nTG2 is expressed in the brain, where it is important in cell adhesion and synaptic stabilization.
\nThese children constitute a subpopulation of autistic children who fall within the autism disease spectrum, and for whom autoimmunity may represent a significant etiological component of their autism.
\nMultiple sclerosis is a chronic disease in young adults. It is caused by the demyelination of the central nervous system cells. It is considered a T-cell-mediated autoimmune disease that is likely caused by exogenous events, such as infectious agents, in susceptible individuals [54].
\nPopulation, family, and twin studies indicate that genetic factors and most likely several genes are associated with the disease, but genetic backgrounds as well as exogenous or somatic events are required to develop the disease. The strongest genetic association with disease among the many candidate genes that were analyzed was demonstrated for HLA-DR15, HLA-DQ2, and HLA-DQ6 [55]. HLA-class II haplotypes such as DR2/DQ6, DR3/DQ2, and DR4/DQ8 show the strongest linkage with the disease.
\nA positive connection of primary progressive MS with DR4-DQ8 and DR1-DQ5 and an association of “bout onset” MS with DR17-DQ2 is be found, while an HLA association with disease severity was not found [56].
\nIt is currently unclear how the expression of a particular HLA class II gene would result in susceptibility to develop an organ-specific autoimmune disease.
\nThe HLADQ2 associated disease risk is known to be modified across individuals or populations varying in ethnic background, geography, or gender.
\nThe presence of genes coding for DQ2 and DQ8 molecules explains up to 40% of the occurrence of celiac disease in European populations. DQ2 is most common in Western Europe; higher frequencies are observed in parts of Spain and Ireland. In European celiac patients, the frequency of the HLA DQ2 is up by 90% e the HLA DQ8 is between five and 10% like was described in Dutch, UK, and Irish cases.
\nDifferences in the frequencies of the HLA genotypes DQ2 and DQ8 in non-European populations have already been described. Patients of Indian origin had a lower frequency of HLA DQ2 than those of British origin. Lower frequencies of HLA DQ2 and higher frequency of HLA DQ8 than Europe have also been described among CD patients in the United States (82% DQ2 and 16% DQ8 only) and in Cuba (86% DQ2) In Chilean celiac patients the genotype DQ8 predominates. The genotypes DQ2 and DQ8 were present in 93.2% of patients with CD in the Northeast of Brazil. The HLA DQ2 was present in 75.6% and DQ8 in 17.8% of these patients.
\nAnother finding from this group is that 79% of the unaffected control families carried genotype DQ2 and/or DQ8, which is one of the highest frequencies so far described among first-degree relatives. Most studies on HLA among first-degree relatives found that no more than 59.5% of first-degree relatives in Europe presented HLA DQ2 and DQ8. Since the frequencies of genetic markers among populations of first-degree relatives reflect and amplify those among the general population of which they form part, in this region, a large proportion of the general population may carry these markers.
\nThe frequencies of the different isoforms of DQ2 were also analyzed. The Eurasian geographic distribution of DQ2.2 is slightly greater than DQ2.5. Compared to DQ2.5, the frequency in Sardinia is low, but in Iberia, it is high reaching a maximum frequency of ~30% in Northern Iberia, and half that in the British.
\nCases of DQ2.2 patients with CD without DQ2.5 are in some populations, particularly in the south of Europe. It extends along the Mediterranean and Africa at relatively high frequency and is found in high frequencies in some Central Asian, Mongolians, and Han Chinese. It does not appear to have an indigenous presence in the West Pacific Rim and DQ2.2 presence in South-east Asia and Indonesia is likely the result of gene flow from India and China in the past. The haplotype shows considerable diversity in Africa. The expansion of DQ2.2 into Europe appears to have been slightly later. DQ2.5 is generally highest in northern, Icelandic Europe, and Basque in northern Spain. Phenotype frequency exceeds 50% in parts of Ireland, which overlaps one of three global nodes of the DQ2.5 haplotype in Western Europe [57].
\nThis work is designed to provide a quick overview of the HLA-DQ2 molecule, analyzing the main points such as molecular structure, gene variants, and the role played by the molecule in the clinical context; dealing not only with the most known autoimmune diseases to which it is linked but also with less known areas of development.
\nThis work aimed to offer a new point of view on the subject, although aware of having only skimmed the topic, we hope to have offered a starting point for any new analysis of the molecule.
\nThis chapter allowed us to analyze HLA in a different context from the most known of compatibility in hematopoietic stem cell transplantation, confirming once again the enormous complexity of the HLA system and its many facets and applications.
\nThe Kupferschiefer is a copper-, polymetallic-, hydrocarbon-bearing black shale of the lowermost Zechstein Group of Permo-Triassic age (252 Ma) in southern Germany and southwestern Poland [1, 2]. It is usually one to two-meters thick and underlies 600,000 square kilometers, extending from Great Britain to Belarus for a distance of over 1500 km (Figure 1).
Map of Zechstein basin showing locations of exotic magnesium minerals, lithium-rich brines, and euhedral quartz [
Copper has been mined from the Kupferschiefer for over 800 years, since its discovery circa 1200 A.D. The top of the Kupferschiefer carbonaceous shale unit coincides with the Permian extinction event and the Permo-Triassic unconformity dated at circa 252 Ma [1, 2]. The brines that deposited the Kupferschiefer metal system were extremely toxic and reduced and may have significantly contributed to the Permian extinction event [3].
Mineralogical, chemical, and geological analyses of the combined Kupferschiefer-Zechstein show strong chemical and paragenetic relationships between the Weissliegend silica extrudites (sandstones), Kupferschiefer carbonaceous shales, and Zechstein salines and dolomitic carbonates. This linkage has led us to a broader, more unified, serpentine-linked model related to deep-sourced, hot, hydrothermal, mud-brine volcanism [1, 2]. The overall Zechstein-Kupferschiefer chemical stratigraphy suggests density- and composition-driven fractionation of deep-sourced, high-density brines that are metal-rich, alkali-rich, silica-aluminum-rich, and halogen-rich.
The Kupferschiefer-Weissliegend contains a world-class copper resource with most of the copper hosted in the Weissliegend. More than 78 million metric tons (Mt) of copper have been produced or delineated as resources, with more than 90 percent of the known mineral endowment located in Poland [4]. Salt resources in the immediately overlying Zechstein saline sequence are also world-class with 102 billion metric tons of economic and subeconomic salt in Poland alone [5]. The salt deposits also contain major resources of magnesium and potassium along with elevated strontium, boron, and lithium [6].
Three hydrothermal heat pulses were posited to represent different stages of dehydration of serpentine in the underlying ultramafic basement [1]. The current paper tests that hypothesis by examining chemical evidence in serpentinite basements for (1) general evidence for dehydration, (2) specific evidence for sequential dehydration, and (3) qualitative mass balance constraints that relate to sequential emplacement of brines in the overlying Kupferschiefer-Zechstein.
This paper also examines possible structures connecting the basement and overlying strata and to what extent a serpentinized zone underlies Poland and Germany. Spieth [2] and Spieth and others [4] added refinements to the high-temperature aspects of the hydrothermal, mud volcanic, mud-brine model. This paper provides an expanded definition of the serpentosphere, especially those emplaced at the base of the crust during flat subduction episodes. This paper also develops a geochemical model that links sequenced dehydration of the serpentosphere with the paragenetic sequence in the overlying Kupferschiefer-Zechstein hydrothermalism and attendant mud volcanism (Figure 2).
Copper sulfide deposition and reaction products inferred in this paper.
The general hydrothermal mud reaction sequence for the Kupferschiefer itself starts with early silica, copper-silver-gold-rich, illitic, carbonaceous (kerogen-rich) shale. The Kupferschiefer-Zechstein sequence rapidly grades upward, becoming more dolomitic up section, with a zinc-rich zone associated with dolomitic carbonate, followed by calcitic carbonate. The carbonates near the base of the Zechstein transition upward into a saline-rich chemical lithocap, which comprises the multi-cyclic, Zechstein chemical sedimentary sequence. The lowest Zechstein cycle is the Werra carbonate, which grades upward into a basal, anhydrite-rich unit that transitions upward into halite. At least two additional cycles, each floored by carbonates, in turn grade upward to halite and then into magnesium- and potassium-chlorides. The Rote Fäule represents a late stage, oxidized, hematitic alteration that post-dated the Kupferschiefer and penetrated upward at least into the basal Werra anhydrite unit of the Zechstein sequence.
The extensive literature on the Kupferschiefer was canvassed [1, 2] and revealed evidence for a hot, hydrothermal, mud volcanism model that was sourced in a serpentosphere layer that had earlier been tectonically emplaced by flat subduction between the crust and mantle (Moho). This paper focuses on the deep crustal sources from which the Kupferschiefer and related strata were possibly sourced. The result is a consistent, crustal-scale model of ultra-deep hydrothermalism (UDH) that is derived from ultramafic sources (serpentosphere) in the lower crust under high energy conditions.
In the mud volcano model, metal-rich brines ascended through deep-reaching faults and erupted as lower temperature slurries on low-relief, shield-shaped mud volcanoes above fractures in an open, shallow inland sea. Metal sulfide deposition is systematically accompanied by co-precipitation of silica, dolomitic carbonate, and muscovite/illite, as well as primary copper chlorides (such as atacamite [CuCl2]) and other brine minerals, such as anhydrite and sylvite [KCl]. Hydrocarbons are also an important co-precipitate [1, 2].
In the mud-volcanic model, the underlying Weissliegend Sandstone is reinterpreted to be a silica-injectite/extrudite complex that was deposited as an early silica mud fractionate of the Zechstein-Kupferschiefer, chemical, mud-brine volcanism [1, 2]. In the main Kupferschiefer copper areas, the Weissliegend contains chalcocite (with minor bornite and illite) in silica matrix. The Weissliegend and Rotliegend host significant oil and gas accumulations in nearby areas. The hydrocarbons may also have a hydrothermal origin that is related to hydrogenation of primary kerogen in the mud-brine plume.
The ultimate brine source is interpreted by Keith and others [1, 2] to be serpentinized peridotite in the lower crust near the Moho transition to the mantle. Dehydration of the serpentinite source to talc (steatization) by mantle heat during failed, intra-continental rifting of the Pangaea supercontinent at the end of Permian time is suggested to have released vast amounts of element-laden, high-density brines into deep basement fractures. The chemical muds were then deposited into and above the Rotliegend Sandstone in the shallow Kupferschiefer-Zechstein sea at the Permo-Triassic unconformity [1, 2].
The Kupferschiefer situation is analogous to modern mud volcanism in the northern Caspian Sea, the 700-km long and 50-km wide belt of mud volcanoes of the Mariana forearc wedge, and Salton Sea gryphons of southern California, USA. The UDH model of a mud volcanic origin of brines integrates the concepts of researchers favoring the hot epigenetic model with those favoring the cold syngenetic model.
Three pulses were identified in the broader Kupferschiefer-Zechstein metallization sequence through examination of the mineral paragenesis and an extensive radiometric age data set reported in a literature survey [1]. These three pulses are represented by the following (with less common constituents in parentheses):
Weissliegend-Kupferschiefer - Cu-Ag (Re, Pb) metallization and hydrocarbon synthesis at 265–255 Ma,
Zechstein - Zn-Cu-Pb-Ag metallization and continued hydrocarbon synthesis and petroleum generation at 250–245 Ma, and
Rote Fäule - Au-(PGE-U-Co-Se) metallization at 245–235 Ma.
The hot, hydrothermal, serpentosphere-sourced, mud volcanic model integrates with several recent observations that are problematic for existing models. These observations include the following:
High- and low-temperature sulfides coexist. High-temperature selenides were identified by microprobe studies conducted by Spieth [2]. Low-temperature sulfide species, such as djurleite and low chalcocite, co-formed in surface or near surface eruptive sites. These low-temperature sulfides appear in the same sample as high-temperature species, such as selenides that would have formed in deeper mud chambers.
Alkylated and hydrogenated kerogens systematically increase up section following abundant copper sulfide deposition in the T-1 horizon.
The possible presence of chloride brines is evidenced by possible primary atacamite that is coeval with copper sulfide deposition in the Weissliegend (Figure 2).
High crystallinity illite (muscovite) was co-deposited with copper sulfides and has closure temperatures at circa 350°C [1].
Alkane oils were produced in an experiment at 350°C from Kupferschiefer black shales under hydrothermal pyrolysis conditions by Lewan and others [7, 8].
Mineral paragenesis in the combined Weissliegend-Kupferschiefer-Zechstein sequence can be characterized as a density-driven fractionation process. Heavier minerals generally appear earlier and deeper in the sequence in the Kupferschiefer and lighter minerals appear later and higher in the Zechstein sequence.
The intimate association of hydrocarbon generation coinciding with sulfide deposition is shown in Figure 3, where a small diapiric body of zoned sulfides projects into the soft marls of the lower Zechstein at the hydrocarbon generation horizon. This relationship demonstrates the hydrogenation effect induced by sulfide deposition from chloride-rich brines, per the chemistry shown in Figure 2. The diapir-like shape of the sulfide mineralization can be inferred to represent a small-scale analog of the vertical pipe-like features present throughout the Kupferschiefer. The entire depositional sequence appears to be more or less coeval and occurred under soft, mud slurry conditions that were migrating upward from high pressure to low pressure.
Immiscible bornite-chalcopyrite-injectite with covellite, solid state exsolution into soft, carbonaceous-dolomitic muds of the Zechstein dolostone, mounted on a stylolite of massive bitumen hydrocarbon. Spremberg DH 131. //Nic. [
Fractionation occurs at all scales within the Kupferschiefer section. At the broad system scale, mineral densities generally become lighter up-section and with decreasing age (Table 1). At the deposit scale (Figure 4), pipe-like features have been intersected by drillholes beneath the Rudna mound. At the district scale (Figure 5), a, high-density, heavy, noble element suite (Au, PGE, U) is associated with the late-stage, Rote Fäule and is present near deep-seated pipes or fault conduits, such as the Odra fault, as documented by Kucha [9]. Many of Kucha’s observations anticipate the perspectives offered here. Deep-seated pipe structures might be located beneath high density, uranium-rich, gamma anomalies along and near the Odra fault [9, 10].
Compound | Formula | Density |
---|---|---|
Carnallite | KMgCl3.6H2O | 1.6 |
Sylvite | KCl | 1.96 |
Kieserite | MgSO4·H2O | 2.6 |
Halite | NaCl | 2.15 |
Anhydrite | CaSO4 | 2.95 |
Kerogen | HC | 1.15 |
Carbon | C | 2.3 |
Quartz | SiO2 | 2.64 |
Calcite | CaCO3 | 2.71 |
Muscovite | KAl2(AlSi3O10)(OH)2 | 2.81 |
Dolomite | CaMg(CO3)2 | 2.88 |
Sphalerite | ZnS | 4.0 |
Chalcopyrite | CuFeS2 | 4.2 |
Pyrite | FeS2 | 4.9 |
Galena | PbS | 7.57 |
Covellite | CuS | 4.61 |
Bornite | Cu5FeS4 | 5.075 |
Hematite | Fe2O3 | 5.26 |
Digenite | Cu9S5 | 5.55 |
Chalcocite | Cu2S | 5.8 |
Palladoarsenide | Pd2As | 10.4 |
Silver | Ag | 10.5 |
Sperrylite | PtAs2 | 10.6 |
Paragenetic sequence and zoning integrated with mineral densities for the Kupferschiefer-Zechstein section (youngest at top).
Deposit-scale cross section of the Rudna deposit showing that smaller-scale pipe structures are also present at larger scales (modified from [
Regional metal zoning in the greater Lubin district and its geographic relationship to the deep-seated Odra fault (adapted from [
The early, high-density, copper-rich mineral suite occurs at the base of the Kupferschiefer in the famous, high copper-grade, T-1 unit and in the more recently mined, Weissliegend basal unit of the Zechstein in the Rudna area of southwest Poland. The copper facies and kerogen mainly formed during the widespread Stage 1 episode.
After a short pause, chalcopyrite-sphalerite- and lesser galena were deposited in the basal Zechstein dolomitic marls. The lead facies and bitumen corresponds to Stage 2. Low-density hydrocarbons and calcitic marls co-formed and continued to form after the dolomitic marls along with pyritic sulfides. The final phases of Zechstein deposition were associated with a low density, saline mineral suite. Within this saline mineral suite, a density-driven zoning is apparent. Higher density anhydrite occurs in the lower cycles and lower density, magnesium-potassium halides (carnallite, kieserite, and sylvite) occur in the higher cycles. Halite deposition is widespread, but appears to be maximized in the middle cycles.
Carbon isotope data for the Kupferschiefer are also consistent with other isotope data that indicate a deep serpentosphere source. The δ13C isotope data for all Kupferschiefer samples are shown in Figure 6 and range from −23 to −28‰ [11, 12, 13, 14, 15, 16, 17, 18]. The Kupferschiefer carbon isotopes completely overlap those of oceanic serpentinite seawater peridotite inclusions. Carbon isotopes from Kupferschiefer plot in the middle of the serpentinite-peridotite-kerogen oil window.
Carbon 13 isotopes in the Kupferschiefer compared with δ13C isotope data from world-wide, serpentine-related and other rocks (Kupferschiefer data from [
Important additional carbon isotope correlations include those for dissolved kerogen (DOC) in deep sea water, saline, hydrothermal fluids from deep marine seeps hosted in basalt on the Juan de Fuca Ridge, and a partial overlap with serpentine-sourced hydrothermal fluids emanating from white smokers at Lost City in the central Atlantic Ocean. There is also a complete overlap with carbon isotopes in world-wide oil. This carbon isotope correlation allows the inference that the serpentosphere described below is the ultimate source of oil, carbonaceous shale, and metallization in the Kupferschiefer.
An isotopic feature that is unique to the Kupferschiefer-Zechstein sulfide system is the extremely light sulfur isotope data at Lubin (Figure 7) [19]. In chalcocite-digenite samples, the δ32S reaches values as low as −39.9‰. Pyrite samples are anomalous and range from −42.01 to −44.9‰. In the early-stage chalcocite-digenite-bornite assemblage in the lower to middle Kupferschiefer, sulfur isotopes range between about −31 and − 40‰.
Sulfur isotopes at the Lubin copper mine (modified from [
In contrast, in the overlying carbonate-marl Kupferschiefer and marl Zechstein carbonates, sulfur isotopes range between −31 and − 20‰. Presumed late-stage tennantite-tetrahedrite veins exhibit distinct heavy δ34S-enriched sulfur isotopes. Similar sulfur isotope patterns were documented by Spieth [2] in the Kupferschiefer deposit at Spremberg, Germany. Hence, the paragenetic sequence of light reductive sulfur isotopes transitioning upward to heavy oxidized sulfur isotopes for Kupferschiefer types of deposits appears to be a general characteristic of the deposit type.
Given the high temperature of the sulfide mineralization documented by Spieth and Keith and others [1, 2], these low values cannot be explained by microbial reduction. Some other reductive mechanism or source is required. Serpentinization of peridotite is the only other known geologic process that we are aware of that can create light δ34S isotopes (Figure 8). These light δ34S serpentines then become a source for subsequent steatization reactions during mantle heat overprinting, such as may have occurred at the end of the Permian.
Comparison of the sulfide and sulfate isotope compositions of serpentinites from Liguria, the Iberian Margin, the Atlantis Massif, and the MARK area (modified from [
Extremely light sulfur isotopes that are associated with late disseminated pyrite in the overlying Zechstein limestones may be explained by low-temperature, conventional microbial reduction in the classic portrayals by Wedepohl [20] for the Kupferschiefer. However at Kupferschiefer, the microbial signature is inferred to be superimposed on an already light sulfur isotope condition that is serpentinite-sourced as in Figure 8.
Only one rock type, oceanic serpentinite, exhibits extremely light sulfur isotopes. When compared with the sulfur isotopes in sulfides in Kupferschiefer rocks [2], it can be argued that brines that were sourced in the serpentine-steatite reaction chamber were buffered at similar low oxidation states. Significantly, oceanic serpentinites have been identified in the Caledonian basement immediately to the southeast of the Lubin and Konrad Kupferschiefer mineral systems southeast of Wroclaw.
An upward-lightening sulfur isotope pattern was observed by Sawlowicz and Wedepohl [21] in the Weissliegend sand extrudite mounds at Rudna. The upward-lightening pattern of sulfur isotopes ranged from δ34S of −39‰ at the bottom of the chalcocite rhythmite section to −44‰ at the top of a composited rhythmite section. The presence of generally light sulfur isotopes allows the interpretation that deep, serpentinite-sourced brines for the slurries began to deposit chalcocite at the base of the Weissliegend. Hydrogen reduction associated with progressive chalcocite deposition from chloride-hydrogen sulfide brines would have led to production of increasingly lighter δ34S isotopes similar to the broader pattern observed by Kościński in Figure 7 [19] and the light sulfur isotope signature of reduced serpentinite sequences.
Keith and others [1] also hypothesized that much of the saline mass residing in the thick (up to 2000 m), Zechstein saline sequence is not derived from surface evaporative processes, but instead consists of saline, exhalative, chemical, hydrothermal brine products derived from deep serpentinite sources. The concept of a deep serpentine source is supported by the frequent occurrence of talc and magnesium chlorite (clinochlore) in muds, and even serpentine (antigorite) in muds at a number of localities (Figure 1) in the Zechstein [1]. An additional serpentine mud locality was reported from the Morsleben salt diapir [6]. Both the Morsleben and Gorleben salt diapirs contain high-lithium brines that were interpreted to represent basement-sourced metamorphic brines [6] and that fit the dehydration narrative discussed below.
Authigenic, Herkimer-habit, quartz crystals contain carnallite in hot, brine fluid inclusions that homogenized at over 200°C in Zechstein salt diapirs. Additional fluid inclusion data reported by Vovnyuk and Czapowski [22] showed that in sylvite-stable, potassium-rich salines, two sets of fluid inclusions were present. The first set ranged from 50° to 62°C, indicating warm hydrothermal conditions attended high-potassium sylvite precipitation from ‘basin brines’. The second set ranged from 82° to 135°C, indicating hot hydrothermal conditions. From the perspective of the deep, hot, serpentine-sourced, mud-volcanic model, these brines may have been sourced at much deeper levels in the crust. For example, sylvite has been reported from fluid inclusions in the Weissliegend copper ore, along with potentially primary atacamite reported by Michalik [23].
The rare mineral rokühnite (iron chloride, also known as ‘black carnallite’) is locally common in carnallite-rich zones at several locations in the Zechstein. To date, rokühnite is not found in other saline localities. The presence of rokühnite may suggest special conditions in the underlying basement whereby both copper and iron were transported in chloride-rich brine to be deposited in overlying carnallite zones of the Zechstein saline sequences.
Keith and others [24] defined the serpentosphere as a thin (about one to ten kilometers thick), nearly continuous, global-scale layer of serpentinite rock that occurs between the crust and mantle. The serpentosphere is composed mainly (90%) of serpentine group minerals (Table 2) [25, 26, 27] . An expanded description of the serpentosphere is included here because the serpentosphere concept is important to the Kupferschiefer origin. Chemical compositions of the three main serpentine group minerals were selected by non-chemical criteria by Page [25] and are shown in Table 2.
Major oxide | Chrysotile | Lizardite | Antigorite |
---|---|---|---|
SiO2 | 41.53 | 41.02 | 42.14 |
Al2O3 | 0.72 | 1.40 | 1.64 |
Fe2O3 | 0.72 | 4.10 | 1.17 |
FeO | 0.62 | 0.42 | 3.73 |
MgO | 40.93 | 39.44 | 38.37 |
H2O+ | 13.54 | 13.29 | 12.10 |
Total | 98.03 | 99.67 | 99.15 |
Energy | Low energy | High energy | |
Temperature | Low temperature | High temperature | |
Fe2O3/FeO | 1.16 | 9.8 | 0.31 |
Number of samples | 31 | 6 | 15 |
The serpentosphere occurs at the transition between the oceanic crust and the peridotitic mantle, which is widely referred to as the Moho (Mohorovicic geophysical discontinuity). The Moho is characterized by a change in P-wave seismic velocities (Vp) that range from 6.8 to 8.2 km/sec (Figure 9). These velocities are also characteristic of serpentine, as characterized by petrophysical laboratories. When interpreting seismic velocity profiles and sections, Vp velocities of 6.8 to 7.3 km/sec indicate lizardite serpentinite and velocities of 7.3 to 7.8 km/sec indicate antigorite serpentinite in serpentinites that have been about 50% serpentinized [26].
Seismic habitats and P seismic wave velocities of the serpentosphere (modified from [
Thicker initial serpentosphere material (about 2.5 km thick) may be generated at relatively shallow depths adjacent to slower spreading ridges, such as the Southwest Indian Ridge [28]. Thinner serpentosphere (about 1.5 km thick) may be generated at moderately fast spreading ridges, such as the mid-Atlantic ridge (shown in Figure 9).
More recent geophysical work has produced seismic-reflection images of the rocks that comprise the Moho (Figure 10). For example, the seismic reflection studies of the northeast Pacific have imaged a reflector layer about 3 km thick beneath a 200 km-long seismic line [29]. The reflectance texture is consistent with shearing that has produced a mylonitic fabric induced by creep of the upper oceanic crust above the peridotitic mantle.
Deep seismic image (200 km long) in the northeast Pacific showing the Moho as a zone of subhorizontal reflectors about 3 km thick (modified from [
Recent seismic evidence now suggests that the Moho is not simply a geophysical feature, but rather is a thin layer of serpentine-dominated rock. Such rocks have been long known, starting with the observations by Steinmann [30] in ophiolite belts that are now sutured into continents. Hess [31] was the first researcher to suggest that there might be a globally distributed layer of serpentinite beneath the ocean basins. Hess noted that serpentine-bearing ophiolites have a world-wide distribution in suture zones within continents [31], which is consistent with the presence of the serpentosphere beneath continental areas.
Serpentosphere occurs in four tectonic settings shown in Figure 11. Briefly, serpentosphere is made by hydrolysis of mantle peridotites adjacent to oceanic spreading centers (upper left diagram in Figure 11). The serpentosphere is then subducted under normal subduction conditions beneath an aesthenosphere-mantle hanging wall (lower left part of diagram), where it sequentially dehydrates to produce hydrous metaluminous arc magmatism in the hanging wall that ultimately intrudes the upper crust to make magmatic arcs.
Schematic diagrams of four major tectonic settings for the serpentosphere (green line) as discussed in this paper. Upper left: generation of serpentosphere at oceanic rift spreading centers. Lower left: subduction of serpentosphere in normally dipping subduction zones. Upper right: flat subduction of oceanic serpentosphere beneath continental crust during oceanic crust-continent assemblies. Lower right: continental rifting and dehydration of formerly underplated serpentosphere by mantle heating during continental breakups.
A less familiar geotectonic setting is flat subduction beneath typically continental upper plates (upper right part of diagram). In such cases, dehydration of the serpentosphere can produce extensive melting of crustal material in the upper plate to produce peraluminous granitoids.
Subsequent rifting of crust that has experienced previous episodes of flat subduction (lower right part of diagram) can then be systematically dehydrated by mantle heat. The continental rift setting is the tectonic setting envisioned for Kupferschiefer-Zechstein types of deposits.
Formation of serpentosphere is started near oceanic spreading centers at the mantle-crust contact (Figure 12 with the explanation in Figure 13). Oceanic fluids are pushed down by the weight of the overlying water column into the oceanic fracture system to the contact between the gabbroic oceanic crust layer and the underlying peridotitic mantle. Regional-scale serpentinization reactions occur at that contact and produce low temperature lizardite/chrysotile serpentine [32].
Generation of serpentosphere at the oceanic Moho adjacent to oceanic spreading centers (from [
Explanation for
Formation of the serpentosphere results from serpentinization (i.e., hydration) of mantle peridotite by seawater (Eq. (1)). The hydration involves adding water and accompanying elements (especially chlorine and carbon) from the seawater into serpentine. The main serpentine group mineral produced at this stage is the relatively low temperature mineral lizardite, along with magnetite and a brine component. Compared to antigorite, lizardite serpentines are much more oxidized and more hydrous.
Magnetite formation produces considerable hydrogen, which can react with existing carbon in the peridotite to make additional kerogen products, which are shown in Eq. (2). The process is exothermic and heat is released during the reaction. These reactions are important regulators for global climate and, ultimately, hydrothermal hydrocarbon formation.
Simplified serpentinization reaction under supercritical conditions (Eq. (1)).
Simplified serpentinization reaction with carbon under supercritical conditions (Eq. (2)).
Once the serpentinization reaction is initiated, continued seawater flux maintains the reaction. Hence, the thickness of the serpentosphere increases progressively away from spreading centers. At the mid-ocean ridge, serpentosphere thickness is near zero, whereas in oceanic crust adjacent to continents well away from the ridge, serpentosphere thicknesses may range up to 10 km or more.
Lizardite serpentosphere is produced under lower pressure, lower greenschist-grade, hydrothermal, metamorphism/hydration of mantle peridotites in oceanic ridge settings. Brine leakage from this reaction (Eq. (1)) produces white smokers (calcite with minor brucite), such as the white smoker field at Lost City in the central Atlantic Ocean. At the on-ridge setting, oceanic brines leach gabbro to produce sulfide-rich black smokers. The carbon in serpentinite is largely added from seawater as shown in Eq. (2).
The extended serpentine reaction (Eq. (2)) introduces carbon into the serpentine-brine system. The carbon component is probably introduced as bicarbonate or dissolved kerogen (DOC in the literature). These carbon compounds are then reacted into the serpentine-brine product system as varying amounts of dissolved kerogen (HC), methane (CH4), formate (CHOO), and carbon dioxide (CO2) brine products. Recent literature shows that reduced carbon species are also present in the deep oceans beneath about 2 km [16] and in submarine vents [17].
Both oxidized and reduced carbon sources can be cycled down to the Moho contact where the serpentosphere and its resultant brine products are made. The brine products can then be cycled back up through the overlying oceanic crust to make submarine vents, such as Lost City, and pock marks on the ocean floor.
In this broader perspective, derivative products, such as oil and life, began their evolution in seawater with serpentine as an important mediator. An important link to creation of life is the presence of formate shown in Eq. (2). Formate potentially is the starting platform on which amino acids, RNA, and ultimately DNA can polymerize. The plastic nature of serpentine also functions as a tectonic ‘grease’ that facilitates plate tectonics.
Compared to the parent peridotite, serpentinites are more magnetic and are lower in density [27]. The coincidence of a magnetic high with a gravity low gives a geophysical signature that can indicate the position of serpentinites at depth beneath or adjacent to ore deposits and oil accumulations, such as richer vents, like Rudna in the Polish Kupferschiefer.
Antigorite serpentosphere is produced via dehydration of lizardite serpentosphere between 300 and 400°C [32] in both normal-dip settings (ocean-continent collisions) and flat subduction settings (continent-continent collisions). The more familiar type of antigorite serpentosphere is formed in normally dipping subduction zones and is later incorporated into alpine collisional orogens as the well-known alpine serpentinites.
A less familiar type of antigorite serpentosphere is formed in flat or shallowly dipping subduction zones. A detailed schematic of flatly subducting oceanic serpentosphere beneath continental crust is shown in Figure 14 with the legend in Figure 15. Flat subduction of serpentosphere is frequently coupled with trench-directed thrust faults that can provide conduits for deep-sourced brines that were generated during dehydration of the underplating serpentosphere.
Schematic cross section of flat subduction emphasizing southwestern North America features, such as the Green River shales [
Explanation for
An example is the latest Laramide, flat subduction beneath western North America in the Paleocene-Eocene. Kerogen in the flatly subducting serpentosphere is typically a high-hydrogen, Type I kerogen that is linked to Type I petroleum accumulations, such as those found in Wyoming, Colorado, and Utah in the Green River, hypersaline shale horizons. In the case of the Kupferschiefer, flat subduction of the Iapetus Ocean serpentosphere beneath northern Europe occurred 135 Ma earlier, making serpentinite available for later dehydration.
Flat subduction of serpentosphere material is a very under-rated geotectonic process. Mature continental areas are characterized by thick Moho, which may be several times thicker than oceanic Moho. The increased thickness may be due to accumulation of several oceanic serpentosphere layers during numerous, previous, flat subduction episodes at the ends of previous orogenies. These thick serpentosphere layers may be variously dehydrated during subsequent rift episodes associated with continental breakups throughout geologic time.
Once serpentospheric materials have been emplaced beneath continental areas by flat subduction, subsequent rifting of the continents creates opportunities for systematic dehydration of the serpentosphere by mantle heat fluxes. Such situations occurred in North America and Europe during the breakup of the Pangea supercontinent near the end of the Permian. A schematic cross section of the results of the dehydration and diapiric processes in rift tectonic settings is shown on Figure 16 [1]).
Schematic model of serpentine diapirs in rift settings, modeled on the Viking Graben structure in the North Sea between Norway and Great Britain in Kupferschiefer time and explanation(from [
A distinguishing feature of rifting and continental breakups is the penetration of the decompression cone down into the deep, lower mantle aesthenosphere. When this deeper penetration occurs, resulting more alkaline diapirs may ascend and interact with the dehydrating serpentospheric material at the base of the rifting and extending continent. These deep interactions may lead to the production of more potassium-rich, alkaline, hydrocarbon deposits (Type II) and their associated brine deposits. These more potassic brines, in turn, lead to the production of much more potassium-rich salines, which precipitate minerals like carnallite and sylvite.
In contrast, in rifting of previously flatly subducted oceanic crust, there is no decompression cone. Instead, shallow, upper mantle, depleted peridotites are hydrated and produce much more sodium-enriched brines that, in turn, lead to sodium-rich trona and nahcolite deposits, such as the Green River hypersaline deposits in the western U.S.
When the above observations are applied to the crust beneath the part of southwestern Poland that contains the Kupferschiefer-Zechstein, a deep serpentosphere pattern is present (Figure 17). In the central Polish velocity profile shown in Figure 17, low-angle, lensoid-shaped packages with Vp (P-wave) velocities [34] that are consistent with both lizardite and antigorite serpentinites are present beneath southwest Poland.
Serpentosphere (Moho) beneath Rudna-Konrad-Spremberg Kupferschiefer (modified from [
A more detailed diagram of geophysical profiles for the Lubin area (Figure 17) has been modified to show the possible relationship of the Kupferschiefer deposits at Lubin and Konrad to metalliferous plumes originating in continental serpentosphere (expressed by numerous sub-parallel reflectors between 6 and 11 seconds). The plumes utilize a deep-seated fault system, which includes faults that penetrate the crust (such as the Odra fault) and which is indicated by breaks/troughs in the magnetic profile. These are adjacent to the Sudetic block, basement high indicated by the gravity high (Figure 17).
Gravity and magnetic profiles for a geophysical line that traverses the Kupferschiefer type deposits on either side of the Fore-Sudetic gravity high [35] show coupled, low-gravity and high-magnetic features are present (Figure 17). The gravity low/magnetic high features indicate the possible presence of deep serpentinite. These features may coincide with a deep-seated feeder system that connects deep serpentosphere crust to the Konrad Kupferschiefer system on the south side and the Lubin system on the north side of the Fore-Sudetic high (Figure 17).
The importance of deep-seated basement flaws, such as the Odra fault system in Poland, is shown in Figure 17. These faults focus heat flow, as well as deep-seated gas fluxes, such as helium that could be generated via serpentinization processes. The presence of such faults can help initiate serpentinite dehydration processes in the lower crust by focusing heat flow from the underlying mantle during continental breakups. An example of continental breakups is the attempted breakup of Pangea in northern Europe in Late Permian. Such a process may have led to development of the Kupferschiefer-Zechstein in the upper crust.
The position of the Lubin district and the Odra fault projected to the section line is of relevance to the mud-volcanic origin of the Kupferschiefer-Zechstein presented in this article. The Odra fault projection coincides with a prominent deflection of the middle crust velocity packages that extend down to the presumed serpentosphere-velocity lenses in the lower crust (Figure 18). For a serpentinite-sourced, ascending, hot brine-mud plume, the upward travel distance is only about 20 km.
Map of Poland and nearby areas showing Teisseyre-Tornquist Zone (TTZ), northeast of which there are no Kupferschiefer type deposits and possibly no underlying Caledonide continental serpentosphere and showing location of the greater Lubin-Kupferschiefer district and its possibly related, deep-seated Odra fault [
Notably, the inferred Caledonide serpentospheric basement is identified in basement massifs southwest of the European Suture zone shown on Figure 18, but does not occur to the northeast of the suture. To our knowledge, no Kupferschiefer-type deposits and no deep serpentosphere geophysical signatures are present northeast of this suture. Thus, the European Suture may place an eastern limit on the occurrence of Kupferschiefer-type systems. The lack of Caledonide basement northeast of the European Suture further emphasizes the inference that the presence of serpentosphere is a necessary condition for the occurrence of Kupferschiefer-type systems.
The presence of serpentinite-bearing ultramafic complexes in the basement of uplifts adjacent to Kupferschiefer types of deposits is also important (Figure 19). The nearby presence of ultramafic sources, such as the Jordanów-Gogolów serpentinite massif [36], is particularly relevant to the deposits in the Lubin district. Rodingite from this massif was dated at 400 Ma [37]. Fluid inclusions within the dated zircons have yielded homogenization temperatures ranging from 268 to 290°C at about 1 kbar. These data place constraints on the temperatures, pressures, and timing of emplacement of serpentospheric materials in the basement beneath the Kupferschiefer and the hydrothermal event associated with rodingite formation.
Map showing the geographic relationship between the Kupferschiefer deposits and potential ultramafic sources in the Variscan/Caledonide basement (maps modified from [
The rodingitization event 135 Ma earlier was not the event that created Kupferschiefer mineralization. The serpentosphere emplacement circa 400 Ma, however, was a necessary precursor condition for the ultimate formation of the Kupferschiefer. Without the presence of the Caledonide serpentosphere, the Kupferschiefer could not have happened. During lizarditization of the oceanic peridotites, key ingredients (such as fluorine, sulfur, copper, and others) were added to the lizardite. These elements would later be added to the Kupferschiefer brines during later dehydration events, starting in the uppermost Permian.
With respect to the continental serpentosphere, data suggest that the serpentospheric materials were emplaced beneath northern Europe during the low-angle subduction event of the Iapetus Ocean circa 400 Ma. This material was then affected by mantle-heat-driven dehydration beneath the Odra and related fault systems beginning about 265 Ma, approximately 135 Ma after the emplacement of the Caledonide serpentosphere. The result is hypothesized to be the Kupferschiefer-Zechstein mineralization.
Results of 15 years of published research in serpentinite terrains, mostly in the Alpine orogen of northern Italy and Switzerland and the Beltic orogen of southern Spain, are summarized in Figure 20. This research has identified three episodes of dehydration of serpentinite, as variously presented in [38, 39, 40, 41, 42].
Pressure-temperature constraints for oceanic lizardite serpentine versus orogenic high-temperature high-pressure antigorite serpentine, higher temperature-pressure chlorite-harzburgite, and highest temperature garnet peridotite showing the first, second, and third dehydration episodes (modified from [
The three dehydration events are now well documented in serpentinite basements and they can be correlated with the three fluid influxes that built the Kupferschiefer-Zechstein sequence. These papers present a wealth of geochemical data that allowed construction of qualitative mass balance constraints for the chemistry that entered the Kupferschiefer-Zechstein brine during the dehydration episodes and, ultimately, resulted in the brine pulses to the surface.
Four stages of serpentosphere evolution are apparent on Figure 20 that pertain to evolution of the Kupferschiefer-Zechstein mineralization. The first stage involves hydration of mantle peridotite in oceanic settings within a few km of spreading centers to create low-temperature serpentine. This serpentine ultimately contains the entire anomalous metal suite that characterizes carbonaceous black shales in the Kupferschiefer [39]. The highly anomalous nature of the combined Cu-Ag-Pb-Zn-Mo-Au-PGE-Ni-V-Cr-HC-S kerogeno-metallic system strongly suggests a deep-seated, ultra-deep hydrothermal (UDH), serpentinized source in the basement. The kerogeno-metallic system correlates with plumes that traveled upward to the seafloor interface via a network of deeply penetrating basement cracks. Various metals are released in a sequential manner through a series of dehydrations.
Figure 20 also shows the three main dehydration events/processes that correlate with three main depositional events in the Kupferschiefer mineralization:
Lizardite to antigorite dehydration creating Weissliegend-Kupferschiefer mineralization (Cu-Ag [Re, Pb, Cl, C, HC]) at 265–255 Ma;
Antigorite to chlorite-harzburgite dehydration creating Zechstein saline sequences (Zn-Cu-Pb-Ag [salts: anhydrite, halite, sylvite, etc.]) at 250–234 Ma; and
Chlorite-harzburgite to garnet-peridotite dehydration creating Rote Fäule (hematite, muscovite, talc, Au-[PGE-U-Co-Se]) at 245–235 Ma.
The overall metal bias and concentration amounts in the serpentosphere are the same as those elements deposited in the Kupferschiefer black shales (for example, Cu, Ag, Hg, Mo, Co, Ni, V, Sb, U, As). In contrast, elements that are not enriched in the Kupferschiefer and that are close to the average detrital shale composition, typically are not enriched in serpentinites (for example, Ba, Sr, Rb, Sc, Nd, Yb, Lu and Sc, as shown on Figure 21).
Composition of Kupferschiefer shale samples (red dots) showing serpentine-affinity metals and oceanic brine components (pink field) as contrasted with average detrital shale (blue plus signs) (modified from [
The apparent correlation of three dehydration events with three metallization events in the Kupferschiefer-Zechstein motivated us to do a more detailed investigation. A major question arising from the above observations is the extent to which element partitioning to the brine phase fits the chemistry of metallization and mineralization patterns in the three stages of Kupferschiefer-Zechstein depositional events.
During this literature study, geochemical information (Table 3) was examined that pertained to the initial hydration of mantle peridotite by seawater to serpentine in reaction chambers adjacent to the oceanic ridge system ([43, 44, 45, 46, 47]). Based on the data, we constructed a series of tables (Tables 4–7), from which qualitative mass balance constraints could be determined for sequential brine evolution via dehydration of serpentine in serpentosphere basements.
Geologic setting/location | Rock type/mineral | Number of samples | Data source |
---|---|---|---|
Hydrosphere | Seawater | Average | [45] |
Oceanic dunite (fresh) Turkey | Dunite | 3 | [46] |
Oceanic dunite (fresh) Burro Mtn. | Dunite | 1 | [47] |
Oceanic dunite (fresh) Vulcan Peak | Dunite | 2 | [44] |
Oceanic harzburgite (fresh) Turkey | Harzburgite | 1 | [43] |
Oceanic harzburgite (fresh) Burro Mtn. | Harzburgite | 3 | [47] |
Oceanic harzburgite (fresh) Vulcan Peak | Harzburgite | 6 | [44] |
Oceanic serpentinite (lizardite) | Lizardite estimated bulk rock | 23 | [38] |
Low T pre-metamorphic lizardite | Lizardite | 7 | [40] |
Oceanic serpentinite (lizardite) | Lizardite/chrysotile mesh data | 46 | [41] |
Oceanic Serpentinite (lizardite) | Lizardite | 4 | [42] |
High-pressure antigorite serpentinite | Est. bulk-rock amounts | 19 | [38] |
Antigorite high temp. Blueschist | Antigorite | 8 | [32] |
Antigorite (Rhoumejon)4 | Antigorite | 83 | [41] |
Antigorite | Antigorite | 8 | [41] |
Olivine-orthopyroxene | Est. bulk-rock amounts | 21 | [38] |
Chlorite-harzburgite | Chlorite-harzburgite | 8 | [40] |
Chlorite-harzburgite | Chlorite-harzburgite | 2 | [42] |
Garnet peridotite | Garnet peridotite | 10 | [40] |
Sources of chemical data used to construct the following tables.
Step | Material | Cl ppm | Li ppm | B ppm | S ppm | C total wt% | Volatile wt% |
---|---|---|---|---|---|---|---|
0 | Seawater | 19,345 | 0.17* | 4 | 411 | 0.003 | |
0 | Average harzburgite-dunite (least altered) | 75 | 1 | 1 | 350 | 0.057 | 1.7 |
1 | Ave. oceanic lizardite serpentinite | 765 | 3 | 67 | 1250 | 0.82 | 14.9 |
Hydration summary | Huge gain | Big Gain | Huge gain | Huge gain | Huge gain | Huge gain | |
2 | Average antigorite | 261 | 3 | 39 | 379 | 0.08 | 13.6 |
3 | Average chlorite-harzburgite | 45 | 5 | 9 | 812 | 0.04 | 1.7 |
4 | Garnet peridotite | n.d. | 3 | n.d. | n.d. | n.d. | 2.7 |
Dehydration summary: Gain (goes to rock) and Loss (goes to fluid) | Big loss (3x), then bigger loss (6x) | No pattern | Loss | Big loss, then gain | Big loss, loss | Loss, huge loss, then gain |
Brine components - bulk chemical data for serpentinite-related rocks arranged by increasing metamorphic grade (data from [6]).
Note: n.d. = no data.
Step | Material | Cu ppm | Pb ppm | Zn ppm | As ppm | Sb ppm | U ppm |
---|---|---|---|---|---|---|---|
0 | Seawater | 0.0009 | 0.00003 | 0.005 | 0.0009 | Below detection limit | 0.0033 |
0 | Average Harzburgite-dunite | 16 | 0.4 | 44 | 0.65 | 0.05 | 0.05 |
1 | Ave. Oceanic Lizardite serpentinite | 22 | 0.33 | 43 | 5 | 0.17 | 0.73 |
Hydration Summary | Slight gain | Slight loss | Same | Gain | Gain | Big Gain | |
2 | Average antigorite | 13 | 0.23 | 36 | 3 | 0.10 | 0.47 |
3 | Average chlorite-harzburgite | 1 | 0.57 | 47 | 0.7 | 0.05 | 0.04 |
4 | garnet peridotite | 25 | 2.34 | 46 | 18 | 0.19 | 0.01 |
Dehydration Summary: Gain (goes to rock) and Loss (goes to fluid) | Big loss, then gain | Loss, then big gain | Loss, then similar | Loss, big loss, then gain | Big loss, then gain | Big loss |
Base metal components - bulk chemical data for serpentinite-related rocks arranged by increasing metamorphic grade.
Step | Material | MgO wt% | Sc ppm | Ni ppm | Cr ppm | V ppm | Rb ppm | Ba ppm | Sr ppm |
---|---|---|---|---|---|---|---|---|---|
0 | Seawater | 0.217 | <0.000004 | below detect. Limit | 0.0002 | 0.0019 | 8.10 | 0.02 | 0.000013 |
0 | Average harzburgite-dunite | 46.06 | 20 | 1893 | 2545 | 28 | 0.20 | 1.00 | 0.47 |
1 | Average oceanic lizardite serpentinite | 37.57 | 6 | 1830 | 2154 | 11 | 0.20 | 1.55 | 8.1 |
Hydration summary | Loss | Loss | Slight Loss | Loss | Loss | No change | Gain | Huge gain | |
2 | Average antigorite | 38.35 | 6 | 1015 | 2168 | 23 | 0.25 | n.d. | 1.95 |
3 | Average chlorite-harzburgite | 42.78 | 11 | 1753 | n.d. | 61 | 0.17 | 0.39 | 3.06 |
4 | Garnet peridotite | 38.79 | 19 | 1513 | n.d. | 68 | 0.27 | 1.77 | 15 |
Dehydration Summary: Gain (goes to rock) and Loss (goes to fluid) | No change, then loss | Gain | Gain, then slight loss | No data | Gain | Loss, then Gain | ?, then Gain | Large loss, then Gain, then huge gain |
Bulk chemical data for peridotite-related and serpentinite-related rocks arranged by increasing metamorphic grade.
Step | Material | SiO2 wt% | TiO2 wt% | Al2O3 wt% | Cr2O3 wt% | MgO wt% | MnO wt% | CaO wt% |
---|---|---|---|---|---|---|---|---|
0 | Average harzburgite -dunite | 44.87 | 0.03 | 0.66 | n.d. | 42.67 | 0.13 | 1.42 |
1 | Ave. oceanic lizardite serpentinite | 41.41 | 0.06 | 1.28 | 0.32 | 37.57 | 0.09 | 0.30 |
Hydration summary | Loss | Gain | Big gain | ? | Loss | Loss | Loss | |
2 | Average antigorite | 43.14 | 0.034 | 1.01 | 0.31 | 38.35 | 0.089 | 0.024 |
3 | Average chlorite-harzburgite | 42.98 | 0.034 | 0.99 | 0.39 | 42.69 | 0.089 | 0.023 |
4 | Garnet peridotite | 43.93 | 0.13 | 3.75 | 0.35 | 38.79 | 0.13 | 3.1 |
Dehydration summary: gain (goes to rock) and Loss (goes to fluid) | Slight changes | No change then gain | No change then gain | No change | Gain then loss | No change then gain | Huge loss, no change then big gain |
Selected whole rock oxide elements, bulk chemical data for serpentinite-related rocks arranged by increasing metamorphic grade.
The elemental data in Table 4 through Table 7 are presented as averages. Given the different sources of information, differing numbers of samples, differing analytical procedures, and differing analytical precisions in the various references, the data should be considered qualitative. Nevertheless, there is enough consistency within the classes and enough numerical differences between the classes that we believe that the average results taken from peer-reviewed literature are qualitatively valid.
Many of the anomalous metals from the Kupferschiefer shown in Figure 21 occur at elevated concentrations in the postulated serpentinite source region in the lower crust. Many of these metals were found during the compilation and were available to be inventoried for their partition into the rock phases or into the brine phases during the various dehydration events. The elements were grouped by their relevance to the sequential brine expulsion model.
Details of locations, rock types, number of samples and sources are presented in Table 3. Samples of fresh oceanic peridotite lithosphere were particularly hard to find, which attests to the pervasive nature of serpentinization at the oceanic crust/Moho contact. Fortunately, field work by Keith located fresh mantle dunites in the Kizaldag ophiolite complex in southwest Turkey. Full petrochemical data for these samples are available from the lead author [46].
Elements partitioned to the brine, which includes Cl, Li, B, S, C, and volatiles (mainly H2O), are presented in Table 4. Base metals (Cu, Pb, and Zn) and related elements (As, Sb, and U) that are variously enriched in the Kupferschiefer-Zechstein plume events [1] are presented in Table 5. Table 6 presents data for elements that are enriched in peridotite (Mg, Sc, Ni, Cr, V) that might be partitioned to brines that deposit these metals in the Kupferschiefer muds. Also, Table 6 presents additional information for Rb, Ba and Sr that would be strongly partitioned to the brine component. Table 7 presents selected whole rock oxide data (SiO2, TiO2, Al2O3, Cr2O3, MgO, MnO, and CaO) that variously reflect elements that may be distributed to the brines that deposited the Kupferschiefer-Zechstein system.
Chlorine and water show the most obvious pattern for evolution from (1) hydration of peridotite to serpentinite, then brine evolution steps (2), (3), and (4) of the sequential dehydration of serpentinite as documented in Table 4. The data show that the peridotitic oceanic lithosphere beneath the oceanic crust contains little water and is hydrated to lizardite serpentinite by the addition of copious amounts of seawater. Chemically, serpentinite is the most hydrated rock on Earth. In oceanic ridge systems, seawater is the only candidate to supply the abundant water, carbon, and chlorine that reside in lizardite serpentine.
The large chemical increases that take place during the conversion of peridotite to serpentinite involve additions of huge amounts of water, halogen, and carbon. Chlorine contents are increased ten-fold, making lizardite serpentinite an excellent candidate for chlorine-enriched brines to supply overlying saline basins. Carbon is augmented twenty-fold, which makes serpentinite an excellent source for hydrocarbon deposits under reduced conditions. In such cases, the carbon travels as reduced, dissolved kerogen (DOC) and is converted to liquid-state hydrocarbons by decompression of the heavy brine fluid in the reservoirs. Water is increased by nine times, making serpentinite the most water-rich major rock type and an excellent source for massive amounts of brine during the dehydration of serpentinite.
In addition, boron and sulfur are added to the rock in abundance and lithium is tripled. Relative to seawater, lithium is at least 15 times higher in serpentinite than in seawater. Hence, serpentinite can provide an abundant source of lithium in brine. Simple evaporation of seawater in the evaporite model does not supply enough lithium as shown in Figure 22. The lithium-enriched brines in the Zechstein diapirs clearly contain much more lithium than would be expected to be evaporative products of normal seawater. A metamorphic source for the lithium in Zechstein salines is suggested in [6]. We suggest that serpentinites in the underlying serpentosphere might provide that source.
Li and Mg concentrations in brine from Gorleben and Morsleben. For comparison, the Li content of the groundwater-monitoring network from Morsleben and the Li content of the rocks from Gorleben are displayed. In addition, the development of the Li content in evaporating seawater (blue line) and the first precipitates from seawater are shown (modified from [
The strong distribution of boron into lizardite serpentinite from boron-poor, fresh peridotite materials indicates that the boron was contributed from the seawater. Hence, the boron in the Zechstein brines is likely to have originated in the seawater that originally made the deep serpentines, and is probably not related to any seawater that might have attended the surface deposition of Zechstein salines.
Once the serpentine source is hydrated and loaded with potential brine elements, it undergoes a series of dehydrations whereby the brine elements (Cl, Li, B, S, and C) are distributed to the brine reaction products (Table 4). The main volume of saline brines in the Zechstein was produced during the second dehydration event, which is associated with the antigorite to chlorite-harzburgite dehydration. There are five cycles of saline deposition in the second phase of Zechstein chemical sedimentation process.
Similar saline sequences appear in other saline basins, such as the Permian Basin in Texas and Michigan Basin in the USA. Considered on a global scale, based on chlorine data in Table 4, it is likely that the second dehydration event of antigorite to chlorite-harzburgite is the most important causal factor in the formation of giant saline deposits.
As the system cooled and collected in mud chambers above the deep source, precipitation of sulfides, such as chalcocite, would have released copious amounts of hydrogen and chlorine, as per the equations in Figure 2.
Chlorine, on a mass basis, appears to be largely lost from the rock during the dehydration of lizardite to antigorite. However, another approximately 5 times (5x) loss occurs during the dehydration of antigorite to harzburgite. These dramatic differences, originally observed by Scambelluri and others [40], are inferred to relate to fluid loss from serpentine dehydration in normally dipping subduction zones. Flatly subducted serpentosphere has not previously been examined for its contribution to volatile regimes that might be emplaced in the overlying crust above the flatly emplaced serpentinites. Dehydration of these previously flatly subducted serpentinites can also lead to extensive saline releases that are deposited at the Earth’s surface in saline basins. The Kupferschiefer-Zechstein sequence is an excellent example of such a process.
In the Kupferschiefer case, the first dehydration provided highly saline brines where any metals that were present would likely have been complexed as metal chlorides. It is also apparent that sulfur is strongly partitioned to the brine component and would have been present in the early Kupferschiefer brines as H2S.
Boron appears to be strongly sequestered in the brine component. It is thus not surprising that boron minerals appear in the overlying Zechstein saline sequences, especially in the later cycles. The major loss of boron in the rock occurs in the second dehydration, which helps to explain the occurrence of boron minerals in the later cycles of Zechstein deposition.
Boron and its δ11B isotopes can be used to track the serpentine dehydration reaction in normal subduction zones [48] as shown in Figures 23–25. Lizardite begins to break down to antigorite at about 300°C and the reaction is completed by about 400°C at depths of about 40 km under blueschist metamorphic facies conditions. This reaction coincides with a large release of the boron component to the brine (Figure 23) and a distinct lightening of the δ11B isotope signature (Figure 24) in dehydrated blueschist-associated serpentinite terranes as established for California serpentinites in the Franciscan assemblage [48].
Boron concentrations in ppm of Zechstein saline deposits (modified from [
δ11Boron stable isotopes of Zechstein saline deposits (modified from [
Schematic cross section of a normally developed subduction zone showing a dehydration sequence inferred from boron isotope trends of dehydrating, deep-slab fluids (adapted from [
The δ11B isotope signature also strongly overlaps with boron isotopic data reported from brackish to briny water in the Gorleben diapir by [49]. This overlap suggests the saline brines in the Zechstein saline deposits may have been derived from low temperature lizardite sources (below about 300°C) that dehydrated between circa 265 and 240 Ma using the timing presented in [1]. This event would correspond to the 1st and 2nd dehydration events enumerated in this paper. There is a strong overlap between about +24 and + 10‰ of δ11B isotopes between unmetamorphosed oceanic lizardite and Zechstein salines. There is also a strong lightening of the boron isotope data in blueschist-associated lizardite and antigorite serpentinites.
The hydrogen release is important because hydrogen released from sulfide precipitation is then available to hydrogenate any pre-existing kerogen that might be traveling as a micro-flocculent or dissolved kerogen (DOC) in the brine. Hydrogenation of the probably Polycyclic Aromatic Hydrocarbon (PAH)-enriched kerogen could lead to alkylation and the formation of alkane hydrocarbons and ultimately lead to generation of oil under hydrothermal conditions.
The above observations are consistent with the tenfold decrease in carbon abundance from the lizardite to antigorite dehydration step. This decrease shows that early Kupferschiefer brines would have been very carbonaceous and very hydrogen-rich due to various sulfide precipitation reactions. Not surprisingly, the Kupferschiefer horizon that coincides with the early-stage brine release is the most carbonaceous unit in the Kupferschiefer-Zechstein sequence.
The likely presence of a dissolved kerogen and kerogen flocculent in early Kupferschiefer carbonaceous brine is also supported by the strong partitioning of bulk carbon to the brine component shown in Table 4. The presence of the kerogen is also supported by the transfer of bulk carbon from seawater to fresh peridotite during lizardite serpentinite formation (Eqs. (1) and (2)). The presence of reduced carbon, probably as kerogen carbon (the TOC term in chemical analyses) in oceanic serpentinite, also supports the likelihood of a carbonaceous brine source. The presence of carbon is documented by Früh-Green and others [18] and shown in Figure 26. In general, the altered peridotites contain up to five times higher total C-concentrations compared to the oceanic gabbros.
Bulk carbon content vs. C-isotope ratios of oceanic gabbros and serpentinites (modified from [
Bulk carbon is non-CO2 carbon [18] and is likely to be reduced kerogen (HC carbon), because graphite carbon is rare in lizardite serpentinite. The higher reduced carbon content is probably supplied by seawater, where hydrogen is created by formation of magnetite in the serpentinite reaction (Eqs. (1) and (2)). Thus, a significant amount of the bulk carbon released to the brine component, as shown by the data in Table 4, is likely to be as kerogen carbon. However, it is also probable that much of this carbon is distributed into carbonate carbon as bicarbonate or dissolved CO2. These carbon compounds are available to precipitate extensive amounts of calcitic and dolomitic carbonate in the overlying, more oxidative, Zechstein saline sequences.
The release of reduced carbon to the brine component during lizardite dehydration to antigorite is consistent with ferric:ferrous ratios of lizardite versus antigorite, as compiled by Page [25] and Coleman [27]. Ferric:ferrous ratios determined for lizardite are 9.8:1 (Table 2). Ferric:ferrous ratios for antigorite are much more reduced with average ferric:ferrous ratio of 0.31:1, which is about 32 times more ferroan. Such reduced ferric:ferrous ratios for antigorite indicate the lizardite to antigorite dehydration occurred under very reduced, hydrocarbon-stable conditions. The brines created under these conditions were very reduced and carried a large component of reduced kerogen capable of reacting to liquid state oil in upper crustal reservoirs. The reduced context of the lizardite to antigorite dehydration helps explain the light sulfur isotopes documented above.
The Kupferschiefer black carbonaceous shales are only one example of a metalliferous, hydrocarbon-rich black shale, and many black shales may have formed this way. These black shales may be chemically distinguished from more aluminum-rich, detrital shales derived from continental granitic sources. Thus, it is an important possibility that carbonaceous black shales in general may have a deep-sourced serpentospheric component.
Since 2014, abundant data for copper (for example in Scambelluri and others [40]) now exists throughout all four stages (one hydration stage and three dehydration stages) of the brine generation process (Table 5). Copper is slightly added to oceanic lizardite serpentosphere from average harzburgite-dunite. Harzburgite, which constitutes the main volume of oceanic peridotite, contains an average between 20 and 34 ppm Cu, which indicates that the formation of lizardite serpentine from mainly harzburgitic peridotite was largely isochemical. However, average copper is lost to the brine by about two times from the lizardite precursor during the first dehydration to antigorite. During the antigorite to chlorite-harzburgite dehydration, average copper is lost to the brine by 13x during the second stage of dehydration. Significantly, copper appears to be retained in the garnet-peridotite rock (perhaps by garnet) during the third dehydration, which would explain the relative absence of copper in the Rote Fäule.
The dehydration sequence for copper explains the copper distribution in the three-fold Kupferschiefer-Zechstein metallized brine sequence. The first two dehydrations produce the copper enrichments observed in the Weissliegend-Kupferschiefer and overlying lower Zechstein (Werra cycle). The third sequence (Rote Fäule) has long been observed to be barren of copper.
Recent literature ([1, 2, 50, 51, 52]) has shown that the Rote Fäule event is a late, overprinting, cross-cutting, copper-poor event. This highly oxidative, hematite-stable, highly acidic event is also copper destructive with respect to the earlier Weissliegend-Kupferschiefer copper mineralization. However, a minor amount of copper might be destroyed and then reprecipitated near the contact with the earlier Kupferschiefer (the so-called ‘transition zone’).
The copper-poor nature of the late third-stage brine is predicted by the dehydration data. Copper contents change from nearly absent (1 ppm) in the chlorite-harzburgite to much richer (25 ppm) in the garnet peridotite. The combination of strong copper partitioning to the second dehydration event and the distribution of whatever copper might be left to the garnet peridotite leads to the expulsion of a copper-poor brine in the third stage dehydration event. Thus, it is no surprise that the Rote Fäule brine is copper-poor.
Whereas the first two stages of the Kupferschiefer-Zechstein depositions were reduced to highly reduced, the third Rote Fäule stage is highly oxidized and hematite stable. This completely different alteration and metal overprint suggests the appearance of a dramatically more oxidizing brine that overprinted the earlier, more reduced stages. The massive volume of Rote Fäule alteration cannot be explained by a simple change in oxidation state of the pre-existing, more reduced brines that had been previously deposited. The appearance of a third independent, more sulfur-poor, oxidative brine event that was independent of the first two brine events appears to be a simpler alternative than a single hydrothermal event that became oxidized in its later history. The source of this third event would be the third dehydration event induced by chlorite-harzburgite to garnet-peridotite dehydration. Unfortunately, no ferric/ferrous data is yet available for the later dehydration event.
Lead, zinc, arsenic, and antimony display similar patterns to that of copper. They are present in more or less equal levels in the early harzburgite precursor and its hydrated lizardite serpentine product, but are strongly lost to the fluid in the first two stages of brine generation. Whatever is left, however, seems to be captured by the garnet peridotite during the third dehydration, which explains the relative lack of enrichment of these elements in the late-stage Rote Fäule.
Another strong characteristic of the Rote Fäule third dehydration overprint is its overall lack of sulfur (Table 4). Sulfur depletion, combined with high oxidation state, explains hematite stability in this sulfur-depleted event. The lack of sulfur in the Rote Fäule coincides with the strong partitioning of sulfur into the garnet-peridotite rock during the third dehydration. The withdrawal of sulfur from participating in third stage brine deposition can largely explain the sulfur depletion that characterizes the oxidized, Rote Fäule hydrothermal plumes.
Whereas the Rote Fäule is barren with respect to familiar Kupferschiefer chemicals such as Cu-S-Pb-Zn-Ag, the Rote Fäule is not barren with respect to other elements. As Pieczonka and Piestrzyňski [53] have shown, significant gold resources have been discovered in and immediately adjacent to Rote Fäule (Figure 27). The gold mineralization is accompanied by significant platinum group elements (PGE) and uranium. Historically, Rote Fäule was considered the ‘death’ of copper mineralization and was avoided wherever it was encountered. However, the discovery of gold, PGE, and U in the Polish Kupferschiefer points to the potential of Rote Fäule as an economic target in existing Kupferschiefer deposits where mining infrastructure exists or can be rehabilitated (e.g., the Mansfeld-Sangerhausen area in Germany). Unfortunately, no data was uncovered for PGE or Au-Ag during this literature survey.
Late, noble metal overprint in the Rote Fäule in the Sieroszowice-Polkowice copper mining district, southwestern Poland (modified from [
The uranium enrichment of the Rote Fäule, as well as other parts of the Kupferschiefer, can be explained as resulting from the strong distribution of uranium to the fluids throughout all three dehydrations. Also, uranium was strongly enriched during the initial serpentinization of the harzburgite step. This uranium enrichment implies that seawater was the primary source of uranium in the serpentosphere as peridotites have little or no uranium enrichment. Seawater was likely also the source of uranium for the uranium expelled during the various dehydrations that were deposited in the overlying Kupferschiefer deposits.
As shown in Figure 21 and Table 6, Kupferschiefer deposits are notable for containing elements common in peridotites, such as Mg, Ni, Cr, and others, which are especially enriched in Kupferschiefer black shale facies. Typical peridotite elements that are enriched and the amount they are increased in Kupferschiefer black shales relative to detrital shale include cobalt (100x), chromium (2x), vanadium (10x), and nickel (5x).
Examination of dehydration data in Table 6 shows that nickel is lost during the lizardite to antigorite dehydration. Whereas there is little change in chrome in terms of brine enrichment, the brines nevertheless may replicate the relative abundance of elements in the peridotite precursor to the Kupferschiefer-Zechstein mineral deposits. A similar pattern is present for magnesium, whereby magnesium remains relatively unchanged through the dehydration process.
Magnesium enrichments observed in the Kupferschiefer-Zechstein sequence may be related to the process of steatization, where talc is created during dehydration of both lizardite to antigorite and antigorite to chlorite-harzburgite. Steatization can be described by the chemical reaction of Eq. (3). Steatization releases water and extra magnesium to a brine component and potentially PGE elements, possibly due to volume changes during steatization from larger volumes of serpentine and destruction of PGE-bearing minerals, such as magnetite and awaruite. It is significant that talc has frequently been observed in the overlying Zechstein carbonates (Figure 1) [1].
Steatization: serpentine plus carbonic acid goes to talc plus Mg-brine (Eq. (3)).
Zechstein carbonates also show a chemical trend that leads to the magnesium corner on a MgO-KAlO2-Al2O3 ternary diagram (Figure 28). Much of the data for the chemical muds is derived from magnesium-chloritic muds that are interfingered with salts in the Zechstein sequence as inventoried by Bodine [54].
Ternary diagram (MgO-KAlO2-Al2O3) showing the contrast between chemical mud from the deep ultramafic mud vs. shallow detrital mud. Green ellipse includes black shale muds from various black shale basins in the continental United States (modified from [
From the perspective of the deep-sourced, hydrothermal, mud volcanic-brine model, chemical muds derived from deep ultramafic sources contain magnesium-rich minerals like serpentine, clinochlore, talc and tri-octahedral clays (saponite) that were formed in high-density chemical brines. Detrital mud contains continentally derived, aluminum-rich minerals, such as kaolinite, pyrophyllite, and di-octahedral smectite (montmorillonite-beidellite series) clays deposited by sedimentary processes, possibly derived from granitic, continental sources.
Data are also presented in Table 6 for rubidium, barium, and strontium. These elements are also typical of Zechstein brines [55], as is rubidium enrichment following potassium in muscovite in the lower Kupferschiefer (T-1) unit. In particular, barium and strontium show strong enrichments in the lizardite product of mantle peridotite hydration by seawater. Seawater is probably the source of the barium and strontium. Strontium is then strongly partitioned to the brine component during the lizardite to antigorite dehydration in step 2. Strontium is then also strongly partitioned into the garnet peridotite rock component in step 4. This pattern explains strontium enrichment as strontianite-celestine in the Zechstein saline sequence, where it occurs as celestine that is closely associated with anhydrite mainly in the upper anhydrite unit and in local, crosscutting veins that one-third of the time are associated with talc. Hryniv and Peryt [55] interpreted the veining as derived from brine introduction from a source outside of the saline section. The talc-celestine association is consistent with a possible ultra-deep brine source.
These above enrichments are observed in so-called ‘carbonate reef’ environments in the middle Zechstein that are associated with hydrocarbon deposition, mainly as gas. The deep-sourced serpentinite model would suggest that both the strontium and hydrocarbons may have a deep source. The enrichment observations also correlate with the mantle helium anomaly documented by Karnkowski [56].
Table 7 shows several percent of silica loss and about 25% aluminum loss to the fluid component during the first dehydration from lizardite to antigorite. This observation may help explain the early abundance of silica in the Weissliegend silica extrudite sand unit, as recently reinterpreted by Keith and others [1] and Spieth [2].
The analogous pattern for aluminum helps to explain the presence of early clays in the Weissliegend and especially the muscovitic clays (illite) in the lower Kupferschiefer black shales.
As with sulfides, precipitation of illite clay produces hydrogen. The electrostatic effects at clay layer boundaries also help in the catalyzation of alkane hydrocarbons from more hydrogen-poor, Polycyclic Aromatic Hydrocarbon (PAH)-kerogens that initially enter the system in its early stages. Little change happens during the lizardite to antigorite dehydration (dehydration 1). Aluminum is partitioned into the garnet during the chlorite-harzburgite to garnet peridotite dehydration (dehydration 3). This progressive sequestering of the aluminum component aids in explaining the transition from aluminum-rich materials in the lower part of the Kupferschiefer sequence to the more carbonate-rich materials in the overlying Zechstein cycles.
Calcium shows a dramatic loss to the fluid during the lizardite to antigorite dehydration, which implies that the brines are strongly charged with a calcium component. However as with aluminum, calcium shows little change during the antigorite to chlorite-harzburgite dehydration and is probably partitioned to the garnet peridotite rock during the third dehydration (dehydration 3).
The data suggest that calcium is progressively available throughout the late Kupferschiefer and early stages of Zechstein deposition, and, along with the sulfur change discussed above, calcium is available to make abundant anhydrite in the lower part of the Zechstein in the Werra cycle. As sulfur is continuously partitioned to the brine component during the first and second dehydration, sulfur abundance appears diminished in the upper Zechstein cycles and late Rote Fäule.
Details of the corresponding serpentosphere dehydrations and mineralization stages in the Kupferschiefer are summarized in Table 8. The three sequential dehydration events are inferred to have been driven by the input of progressively higher amounts of mantle heat that were focused on deep serpentosphere crust near the base of deep-seated fault conduits, such as the Odra fault system. Based on extensive studies of dehydrated serpentinites in the Alpine and Beltic orogens, the earlier releases from the serpentines to the brines feature Na, Ca, and Cl, whereas the later releases contain more K, Rb, and Ba. This geochemistry is consistent with the chemo-stratigraphy of the Zechstein, which features more K- and Mg-rich saline brines in the upper cycles.
Kupferschiefer system formations | Stage | Process | Product of fluid release: metals/chemistry | Main minerals | Carbon |
---|---|---|---|---|---|
Start | Unaltered mantle peridotite generated at spreading centers | Elevated Ni, V, Mg, Cr, Co, PGE, bicarbonate, CO2, minor S, K, Ca, Br | Harzburgite rock enstatite and spinel; dunite of olivine, minor spinel | Kerogen in very small amounts | |
Seawater | Elevated Cl, Na | Dissolved NaCl | Elevated bicarbonate CO2 | ||
Hydration | Add oceanic peridotite + seawater to make lizardite | Add Cl, S, Sr., Ca, Al, C, H2O, B, U, Ba, Na | Lizardite serpentine = lizardite + magnetite + minor brucite | Minor calcite, expansion of kerogen component, minor magnesite | |
Weissliegend-Kupferschiefer | Dehydration 1 releases brine fluids to make Weiss-liegend-Kupferschiefer | Dehydrate lizardite to antigorite | Cu, Ag, early K-Rb, Al, Si, late Ca-Mg, Pb, As, sulfide S, light S isotopes, neutral to mildly acid | bornite, chalcocite-digenite, minor chalcopyrite silica sand, early illite clay, late dolomite marls, late minor calcite | reduced C, kerogen, PAH-enriched |
Zechstein | Dehydration 2 releases brine fluids to make Zechstein salines | Dehydrate antigorite to chlorite- harzburgite | Cu-Ag-Pb-Zn, minor As, Sb, Bi; CO2, Ca-Mg, high NaCl, max. Sulfate S, sulfide S, heavier S isotopes, mildly acid | major chalcopyrite sphalerite, galena, tennantite, dolomite, anhydrite, later halite, bitumen (oil) | reduced C, alkane-enriched oil, bitumen (oil) |
Rote Fäule | Dehydration 3 releases fluids to make Rote Fäule | Dehydrate chlorite- harzburgite to garnet peridotite | Fe (U, PGE, Au, Ag [Cu, Pb, Zn]), very oxidized, very low pH (acid) | hematite, kaolinite, muscovite, | asphaltenic kerogen and PAH |
Stages in formation of Weissliegend-Kupferschiefer to Rote Fäule correlated with corresponding dehydrational stages of the underlying serpentosphere.
This study has shown that a mineralogical and geochemical connection can be drawn between the chemical stratigraphy of the Kupferschiefer-Zechstein and the chemistry and mineralogy of the underlying serpentosphere basement that occurs in structurally uplifted blocks between Zechstein ‘basinal’ lows.
The basins are likely created by withdrawal of mud and brine from the underlying mud-volcanic chambers. The connection is further reinforced by a tri-part, pulsed chemical stratigraphy that includes:
Chemical mud-brine volcanism (early carbonaceous digenite-chalcocite in Kupferschiefer black shale),
Later dolomitic bornite-chalcopyrite-tetrahedrite in Kupferschiefer-Zechstein (with minor sphalerite and galena), and
Epigenetic hydrothermal pulses (late hematitic, gold, PGE, minor U) in the Rote Fäule).
This pulsed chemical sequence, at least in part, can be matched with a tri-partite, pulsed dehydrational sequence that may have affected the underlying serpentosphere during Permo-Triassic time. Each pulse reflects a progressive heating and dehydration of the serpentinite basement that released various chemical components that reflect the increased thermal heating. In this mud-volcanic model, the Kupferschiefer-Zechstein sequence represents brine products formed during the first and second dehydration events in the serpentinite basement. In contrast, the Rote Fäule reflects oxidized Fe-Au-PGE (U), high salinity brines driven off during later thermalism associated with the third dehydration event described above.
This deep-sourced, chemical mud volcanic-brine model satisfactorily explains most of the major, often strongly contradictory, observations on the Kupferschiefer-Zechstein. Some of these contradictory juxtapositions include different age dates for different minerals in the same rock and the juxtaposition of high temperature and low temperature mineral assemblages in the same rock. These apparently conflicting observations are ultimately explained by a ‘deep-to-seep’ model originating in the hot, deep serpentosphere and extruding into a cooler, shallow, seep environment on the shallow sea or lake bottom.
This model of deep-sourced mud-brine volcanism not only explains the Kupferschiefer conundrums, but also explains many other geologic puzzles, for example the origin of oil and other Kupferschiefer analogs, such as the Zambian copper belt. The dehydration model also explains the mass balance problem for salines in salt basins. The evaporative model typically requires too much seawater with a chemical composition different from that observed in many saline basins, especially the Kupferschiefer-Zechstein.
The main goal of this paper was to investigate the chemical correlation between the three-fold dehydration sequence of serpentine in the lower crust and the three-fold mineralization sequence in the Kupferschiefer-Zechstein in the uppermost crust. Another goal was to examine evidence for a continental serpentosphere layer beneath Poland and Germany. A final goal was to examine additional evidence, such as carbon and sulfur isotopes in the Kupferschiefer descriptions, for additional evidence of a deep source.
Abundant evidence was found in the geologic and geophysical literature that a continental serpentosphere layer exists as a several km thick layer that has P seismic wave velocities (Vp) of 6.8–7.8. Serpentinite is also a common rock in the pre-Carboniferous basement of Caledonide age (380–450 Ma) that exists in the basement massifs adjacent to the Kupferschiefer occurrences.
Regional-scale, deep-seated fault systems, such as the Odra fault, provide a plumbing system through which fluids can ascend from any dehydrational events that occurred in the lower crust. These dehydration events acted on the 135-million-years earlier, low-angle, tectonic emplacement of Caledonide ultramafic basement beneath northern Europe.
During the late Paleozoic assembly of the Pangea continent, mantle heat flow focused in the basement and started to dehydrate the underlying ultramafic serpentosphere. The dehydrational, high-density, hot, hydrothermal, mud-brine products were then focused into the deep-seated fracture system. The mud-brine products accumulated as numerous, low-relief, mud-volcanic fields and shallow basins developed on the Permian unconformity above the Rotliegend.
The three-fold dehydration sequence of serpentinite and resulting depositional sequence (Table 8) occurred in the following stages:
Step 1 dehydration of lizardite to antigorite produced highly reduced, Cu-Ag-Fe-Si-kerogen-chloride-charged brines with elevated Ni, V, Mg, Cr, and Co with very light sulfide δ34S isotopes (265–255 Ma). This first stage dehydration correlates with chemical mud-brine volcanism (early carbonaceous digenite-chalcocite) in the Kupferschiefer black shale.
Step 2 dehydration of antigorite to chlorite-harzburgite produced reduced, Cu-Ag-Pb-Zn chloride brines with elevated As, Sb, Bi, CO2, Ca, and Mg with heavier sulfide S isotopes (250–245 Ma). This second stage dehydration correlates with later dolomitic bornite-chalcopyrite-tetrahedrite in Kupferschiefer-Zechstein (with minor sphalerite and galena).
Step 3 dehydration of chlorite-harzburgite to garnet produced very acid, very oxidized, hematite-stable Fe, Au, Ag, PGE, REE brines (245–235 Ma). This third stage dehydration correlates with epigenetic hydrothermal pulses (late hematitic, gold, PGE, minor U) in the Rote Fäule.
This sequence, which was hypothesized as a product of dehydration of the basement serpentinite, was examined in more detail by compiling chemical information from a three-fold, dehydrational sequence of serpentinite found in Alpine orogens. Chemistry compiled from the literature, as well as from unpublished MagmaChem data, shows that element distribution into the various brine systems correlates with that found in the three-fold Kupferschiefer depositional sequence.
The first two stages in the sequence contain a high percentage of high-density mud that accumulated as mud volcanoes on the Rotliegend unconformity. The third dehydration stage (Rote Fäule) was much more water-dominated and had lower pH. The Rote Fäule was emplaced as a late-stage overprint that destroyed the pre-existing Weissliegend-Kupferschiefer-lower Zechstein mineralization and replaced it with a hematite-stable Au-PGE-U-enriched mineralization that is not yet fully explored.
The specificity of the deep-seated, hot, hydrothermal, mud-volcanic model provides explanatory power that does not exist in previous, more compartmentalized models. The mud-volcanic model presented here embraces not only the narrow data set of the Kupferschiefer, but also places it in a broader perspective that includes the entire Weissliegend-Kupferschiefer to Zechstein to Rote Fäule sequences.
Beyond its implications for the Kupferschiefer-Zechstein, the ultra-deep hydrothermal (UDH), mud-volcanic model has implications for the origins of the so-called ‘red bed copper’ model. The red-bed copper deposits can also be interpreted as deep-sourced, chemical, exhalative sediments, with an ultra-deep serpentospheric source for hydrocarbons in general and oil in particular.
Much of this research would have been impossible without the generous financial support and intellectual stimulation provided by staff initially at StatOil and later at DetNorske (now Aker BP) companies in Norway. In particular, Hans Konrad Johnsen, Håkon Gunnar Rueslåtten, Martin Hovland, Jens Emil Vinstad, Jon Eric Skeie, and Christine Fichler in Norway and Monte Swan in Evergreen, Colorado, were very helpful. Prof. Massonne and Dr. Tillmann Viefhaus of the Mineralogical Institute at the University Stuttgart, Germany, for many years supported groundbreaking, detailed mineralogical, geochemical, isotopic, and geometallic basic research. Dr. Bernhardt and Dr. J.C. Kopp guided the geological-mineralogical understanding of the German Kupferschiefer occurrences. Recent conversations with Ziegbniew Sawlowicz have contributed to our knowledge of the Lubin district. An early review by Martin Hovland significantly improved the manuscript and special illustrations by Peg O’Malley greatly improved the manuscript.
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