Results of electron microprobe analysis and paragenesis of pyrite in Dure section (DO) and Sinjar section (SO). Elements in wt%.
The samples of the mineralization of Pb-, Zn-, and Fe-sulfides were collected from three localities (Dure, Lefan, in the northern Thrust zone; and Sinjar, in the Foothill zone) in Northern Iraq. The geochemical recognition using X-ray diffraction (XRD) affirms the presence of the ore deposit sulfides (pyrite, sphalerite, galena, smithsonite, and cerussite). The characterization of mineral chemistry using electron microprobe analysis (EMPA) gives a clear and exact percentage of each element in each mineral. Fluid inclusions are mostly liquid H2O and/or water vapor, which may also contain lesser soluble salts and slightly ore elements. Some fluid inclusions contain CO2 vapor. This occurrence suggests the presence of two immiscible phases due to boiling at the time of their trapping. They are of epithermal system. The homogenization temperatures and salinities obtained for fluid inclusions can be comparable to those reported for the Mississippi Valley Type (MVT) lead-zinc deposits. It is concluded from the petrographic evidence, fluid inclusions and stable isotope data that lead-zinc mineralization was formed due to deeply circulating high-temperature fluids (brines) within the source basin, or later on by tectonic processes, which possibly contribute in leaching metals from either the diagenesis of host rocks or dewatering of deeper buried siliciclastic beds.
- Northern Iraq
The Northern Iraqi Thrust zone and Foothill zone, where the three studied sections of the present study (Dure, Lefan, and Sinjar) are located, is considered as a good place of mineralization of many ore deposits, especially the lead-, zinc-, and iron-sulfides. This is because the structural, tectonic, and lithologic factors made essentially the highly fractured dolomitized limestones act as host rocks for this mineralization. Few detailed studies have been published which deal with the ore deposit mineralization in the area. First, Al-Bassam et al.  mentioned and studied the presence of lead and zinc sulfides. Then, other studies have been accomplished, but the more recent detailed geochemical investigation and exploration were carried out by Awadh [2, 3] and Shingaly . The present chapter deals with the mineralization of sulfides in the above-mentioned three sections. It is worth to mention that this mineralization in Sinjar area is given for first time in such geochemical point of view. The work is a part of PhD research performed at Mosul University by the second author. The geochemical prospect of this work aims first to document the presence of the mineralization of the sulfide ore deposits in Northern Iraq, and second to elucidate their paragenesis, their source, and the processes responsible for their occurrence through the analysis of data obtained by the techniques of X-ray diffraction (XRD), electron microprobe analysis (EMPA), fluid inclusions, and stable isotopes of 13C, 18O, and 34S.
The area of study had been influenced by Alpine orogeny that affected strongly the northern part of Iraq. During the time from Permian to mid-Cretaceous, the northern to eastern parts of the Arabian plate were subsiding gradually and bordering the Neo-Tethys Ocean . The northern thrust zone on the Iraqi territories is formed to be as a developed ridge at the Arabian plate throughout the Zagros suture formed within the domain of the Neo-Tethys. During the movement of the Arabian plate and Tethys development, the mineralization of ore deposits occurred in the area as documented by Al-Bassam et al. , and later on by others as, for example, Awadh . The host carbonate rocks of the ore deposits are represented mostly by fractures and karstified dolomitized limestones of Qamchuqa and Mergi formations (Middle Cretaceous), Bekhme formation (Upper Campanian), marly limestone of Shianish formation (Upper Campanian-Maastrichtian), and Kurra Chine formation (Upper Triassic) [6, 7].
The general geology and locations of the three studied sections (Dure, Lefan, and Sinjar) are illustrated in Figure 1 .
Representative samples were analyzed using a Philips X-ray diffractometer (PW3710) scanning from 4° to 60° 2θ. The generator was controlled using Philips PC-APD software. Peak identification was enabled using PDF/ICCD database and quantification using Rietveld analysis using commercial program Siroquant (Sietronics, Australia). Analysis was done at laboratories of the Department of Earth Sciences, Royal Holloway of London University.
Quantitative chemical analyses for selective host and sulfide minerals from the studied lead-zinc deposits were obtained from 10 polished sections (carbon coated) with a Cameca 3-spectrometer electron microprobe at University-College London UCL, UK. A defocused 15–25 μm beam was utilized at an accelerating voltage of 15 kV, a sample current of 15 nA, and a counting time of 10 s.
Fluid inclusions were observed under petrographic microscope, and the following parameters were determined by microthermometry: highest temperature of ice melting (last ice melting temperature) (Tm) and homogenization/filling temperature (Th) measurements. Eight double-polished thin sections were prepared from the carbonates (dolomite and calcite) and sphalerite. The microthermometric measurements were taken on a NIKON Labophot-pol microscope mounted with LINKAM THMS-600 and TMS-92 freezing-heating stage and long-distance LW40x objective, in Iran Mineral Processing Research Center (IMPRC), and one sample was also carried out at Geological Engineering Department of Cumhuriyet University in Sivas/Turkey.
Mineral separates for sulfur isotope analysis were acquired by handpicking, and samples were converted to sulfur dioxide gas using a VG Isotech SIRA II mass spectrometer and using laboratory standard gas as a reference to produce true δ34S. The standards employed were the international standards NBS-123 and IAEA-S-3, and the SUERC standard CP-1. Analyses were made at an NERC Isotope Community Support Facility, SUERC, Glasgow, Scotland.
4. Geochemistry of ore deposits
XRD diffractograms definitely illustrated the specific recognition of the sulfides (pyrite, FeS2; sphalerite, ZnS; galena, PbS; smithsonite, ZnCO3; and cerussite, PbCO3) ( Figure 2 ).
The data provided in Tables 1 – 3 reveal clearly the chemistry of pyrite, sphalerite, and galena, respectively. The pyrite in Table 1 composes mainly of 44.7–47.5 wt% Fe and 46.6–55.1 wt% S. The sphalerite in Table 2 composes essentially of 53.6–69.1 wt% Zn and 31–35.9 wt% S. The galena in Table 3 composes mainly of 79.9–87.9 wt% Pb and 13.1–14.7 wt% S. Moreover, the calculations of their chemical formulae are given in Tables 4 – 6 . The general paragenesis of pyrite, sphalerite, and galena of the three studied sections is illustrated in Figure 3 . Pyrite is shown to be present in the three localities, where it is more abundant in both main and late stages at both Dure and Sinjar, while it is more abundant in both early and main stages at Lefan.
|Sample no.||Chemical formula||Ore stage|
|DO 20-1||Fe(.955 As.042 Zn.001 Cu.001) S2||Early|
|DO 20-2||Fe(.963 As.035 Cu.001) S2||Early|
|DO 20-3||Fe(.965 As.035) S2||Early|
|DO 25-1||Fe(.96 As.04) S2||Early|
|DO 25-2||Fe(.98 As.02) S2||Early|
|DO 20-1||Fe(.91 As.06 Pb.002 Zn.03 Cu.003 Co.001) S2||Main|
|DO 20-2||Fe(.93 As.04 Zn.03) S2||Main|
|DO 20-3||Fe(.97 As.03) S2||Main|
|DO 20-4||Fe(.96 As.02 Zn.02) S2||Main|
|DO 20-5||Fe(.97 As.02 Pb.01) S2||Main|
|DO 20-6||Fe(.98 As.02) S2||Main|
|DO 25-1||Fe(.99 As.001 Pb.001 Zn.001 Cu.002 Co.002) S2||Main|
|DO 25-2||Fe(.98 As.02) S2||Main|
|DO 25-3||Fe(.99 As.001 Cu.002 Co.002) S2||Main|
|DO 25-4||Fe(.995 As.002 Pb.001 Co.001) S2||Main|
|DO 26-1||Fe(.995 As.001 Pb.001 Zn.001 Co.001) S2||Main|
|DO 26-2||Fe(.96 As.02 Zn.02) S2||Main|
|DO 26-3||Fe(.973 Pb.001 Zn.023 Cu.003) S2||Main|
|DO 26-4||Fe(.99 Zn.01) S2||Main|
|DO 26-5||Fe(.94 As.05 Zn.007 Cu.003) S2||Main|
|DO 26-6||Fe(.995 Pb..001 Zn.004) S2||Main|
|DO 25-1||Fe(.988 As.004 Cu.008) S2||Late|
|DO 25-2||Fe(.999 Cu.001) S2||Late|
|DO 25-3||Fe(.985 As.002 Zn.012) S2||Late|
|DO 25-4||Fe(.97 As.004 Pb.001 Zn.024 Cu.001) S2||Late|
|DO 25-5||Fe(.942 As.033 Pb.001 Zn.023 Cu.001) S2||Late|
|DO 25-6||Fe(.877 As.017 Pb.002 Zn.104) S2||Late|
|DO 25-7||Fe(.925 As.031 Pb.009 Zn.034 Cu.001) S2||Late|
|DO 25-8||Fe(.925 As.029 Pb.008 Zn.037 Cu.001) S2||Late|
|SO 4-2||Fe(.999 Zn.001) S2||Main|
Sphalerite at Dure is more abundant in the main stage, while at Lefan it is more in both main and late stages. In Sinjar it is recorded only in the late stage with few abundance.
Galena is found more abundant in late stage and less in the main stage at Dure, while it is more in the main stage than in the late stage at Lefan, and no galena is recorded at Sinjar.
Pyrite varies in composition as shown in Table 4 . At Dure, the pyrite of the early stage has mainly arsenic as traces in Fe-site (As.02–.042); other lesser traces are of zinc and copper (Zn.001; Cu.001). In the main stage, pyrite has relatively more arsenic reaching up to As.06, while other traces (Zn.001–.104, Pb.001 Cu.002–.008 and Co.001–.002) may be found .In the late stage, pyrite has no difference in arsenic content than that of the early stage (As.002–.04). The pyrite at Sinjar is very pure (FeS2); only Zn.001 is recorded. At Lefan, no data are available.
Sphalerite as shown in Table 5 is also noticed to have traces of Fe.001–.095 and Cd.002–.003 in the Zn site of its chemical formula of all stages at Dure, whereas at Lefan, sphalerite has sometimes only Fe.13–.17 in its formula in both early and main stages, which is more than that at Dure; in other samples, there is Cd.001–.004 that is recorded in all stages. At Sinjar, sphalerite has also Fe.005 and Cd.001 in the Zn site.
|Sample no.||Chemical formula||Ore stage|
|DO 26-1||Zn(.908 Fe.089 Cd.002) S||Early|
|DO 26-2||Zn(.923 Fe.074 Cd.002) S||Early|
|DO 26-3||Zn(.894 Fe.104 Cd.002) S||Early|
|DO 26-1||Zn(.885 Fe.113 Cd.002) S||Early|
|DO 30-1||Zn(.903 Fe.095 Cd.002) S||Main|
|DO 20-1||Zn(.928 Fe.069 Cd.002) S||Main|
|DO 20-2||Zn(.935 Fe.063 Cd.002) S||Main|
|DO 20-3||Zn(.933 Fe.065 Cd.002) S||Main|
|DO 20-4||Zn(.935 Fe.063 Cd.002) S||Main|
|DO 25-1||Zn(.956 Fe.042 Cd.002) S||Late|
|DO 25-2||Zn(.983 Fe.014 Cd.002) S||Late|
|DO 25-3||Zn(.966 Fe.031 Cd.002) S||Late|
|DO 25-4||Zn(.955 Fe.042 Cd.003) S||Late|
|DO 25-5||Zn(.952 Fe.045 Cd.003) S||Late|
|DO 25-6||Zn(.995 Fe.003 Cd.002) S||Late|
|DO 25-7||Zn(.985 Fe.012 Cd.003) S||Late|
|DO 25-8||Zn(.981 Fe.017 Cd.002) S||Late|
|DO 25-9||Zn(.977 Fe.021 Cd.002) S||Late|
|DO 30-1||Zn(.984 Fe.014 Cd.002) S||Late|
|DO 30-2||Zn(.995 Fe.002 Cd.002) S||Late|
|DO 30-3||Zn(.996 Fe.002 Cd.002) S||Late|
|DO 30-4||Zn(.995 Fe.002 Cd.003) S||Late|
|DO 30-5||Zn(.997 Fe.001 Cd.002) S||Late|
|DO 30-6||Zn(.993 Fe.004 Cd.002) S||Late|
|DO 30-7||Zn(.99 Fe.008 Cd.002) S||Late|
|DO 30-9||Zn(.993 Fe.005Cd.002) S||Late|
|DO 30-10||Zn(.996 Fe.001 Cd.002) S||Late|
|LO 10-1||Zn(.83 Fe.17) S||Early|
|LO 10-2||Zn(.818 Fe.18 Mn.001 Cd.001) S||Early|
|LO 10-3||Zn(.811 Fe.187 Mn.001 Cd.001) S||Early|
|LO 18-1||Zn(.87 Fe.13 ) S||Main|
|LO 18-2||Zn(.87 Fe.13 ) S||Main|
|LO 18-3||Zn(.871 Fe.128 Cd.001 ) S||Main|
|LO 18-4||Zn(.862 Fe.134 Cd.004) S||Main|
|LO 18-1||Zn(.935 Fe.061 Cd.004) S||Late|
|LO 18-2||Zn(.938 Fe.061 Cd.001) S||Late|
|LO 18-3||Zn(.936 Fe.062 Cd.002) S||Late|
|SO 4-1||Zn(.994 Fe.005 Cd.001) S||Main|
|Sample no.||Chemical formula||Ore stage|
|DO 26-1||Pb(.999 Fe.001) S||Main|
|DO 26-2||Pb(.999 Fe.001) S||Main|
|DO 26-3||Pb(.996 Fe.001 Zn.003) S||Main|
|DO 26-4||Pb(.999 Zn.001) S||Main|
|DO 25-1||Pb(.863Fe .016 Zn.117 Cd.003) S||Late|
|DO 25-2||Pb(.858 Fe.006 Zn.131 Cd.005) S||Late|
|DO 25-3||Pb(.856 Fe.012 Zn.128 Cd.004) S||Late|
|DO 25-4||Pb(.879 Fe.011 Zn.106 Cd.004) S||Late|
|DO 25-5||Pb(.872 Fe.009 Zn.116 Cd.003) S||Late|
|DO 25-6||Pb(.794 Fe.029 Zn.173 Cd.003) S||Late|
|DO 25-7||Pb(.943 Fe.005 Zn.047 Cd.005) S||Late|
|DO 25-8||Pb(.917 Fe.005 Zn.074Cd.004) S||Late|
|DO 25-9||Pb(.836 Fe.003 Zn.156 Cd.004) S||Late|
|LO 10-1||Pb(.986 Fe.002 Zn.012 ) S||Main|
|LO 10-2||Pb(.988 Fe.001 Zn.011) S||Main|
|LO 10-3||Pb(.916 Zn.081 Cd.004) S||Late|
|Sample no.||Tm (°C)|
Ice melting temperature
|Salinity wt% NaCl equivalent||Origin||Mineral|
|Deposit locality||Sample||Mineral||δ34S ‰||Author(s)|
|Dure||DO 25||Pyrite||0.9||Present study|
|DO 22||Pyrite||1.3||Present study|
|DO 15||Pyrite||1.6||Present study|
|Pyrite||0.2||Al-Bassam et al. |
|Pyrite||3.6||Al-Bassam et al. |
|DO 22||Sphalerite||2.4||Present study|
|DO 30||Sphalerite||2.0||Present study|
|Sphalerite||0.0||Al-Bassam et al. |
|Sphalerite||−0.4||Al-Bassam et al. |
|DO 28||Galena||1.8||Present study|
|DO 30||Galena||−0.9||Present study|
|Galena||−1.8||Al-Bassam et al. |
|Galena||−2.6||Al-Bassam et al. |
|Lefan||LO 22||Pyrite||3.6||Present study|
|LO 15||Sphalerite||1.8||Present study|
|LO 15||Galena||1.2||Present study|
|LO 18||Galena||0.47||Present study|
|Sample||Lithology||δ13CPDB (‰)||δ18OPDB (‰)||δ18OSMOW (‰)|
|DK 90||Dolomitized lime-mudstone||−1.05||−4.48||26.24|
|DK 84||Black dolomitic shale||0.60||−8.48||22.12|
|DK 80 *||Fine dolomitized limestone||1.23||−7.71||22.91|
|DK 70 *||Brecciated dolostone||1.16||−6.94||23.71|
|DK 65 *||Saddle dolomite||−1.25||−11.93||18.56|
|DK 58 *||Smithsonite (ZnCO3)||−2.77||−10.09||20.46|
|DK 45||Coarse dolomitized limestone||0.59||−5.49||25.20|
|DK 32||Coarse gray dolostone||−1.57||−9.01||21.57|
|DK 25||Bioclastic lime-mudstone||−1.30||−8.70||21.89|
|DK 18||Brecciated dolomitic limestone||−2.80||−8.48||22.12|
|DK 10||Bioclastic lime-wackstone||−1.00||−9.01||25.01|
|LSh 1||Packstone (limestone)||0.31||−4.53||26.19|
|LB 68||Coarse dolostone||1.93||−8.19||22.42|
|LB 64||Dolomitized lime-wackstone||−0.41||−5.67||25.01|
|LB 60||Dolomitized lime-wackstone||2.23||−4.83||25.88|
|LB 55||Dolomitized lime-wackstone/packstone||1.37||−5.37||25.32|
|LB 53 *||Dolostone with saddle dolomite||−2.53||−7.04||23.61|
|LB 35 *||Dolomitized lime-packstone||1.61||−5.20||25.50|
|LB 32 *||Dolomitized lime-grainstone||0.96||−6.15||24.52|
|LB 31 *||Recrystallized limestone||0.94||−5.93||24.75|
|LB 28||Dolomitized lime-grainstone||−3.34||−7.13||23.51|
|LB 25||Dolomitic limestone||1.28||−3.77||26.98|
|LB 20||Recrystallized lime-wackstone||1.13||−5.91||24.77|
|LB 17||Dedolomitized dolostone||1.24||−4.87||25.84|
|LB 12||Rudist boundstone (limestone)||1.27||−3.94||26.80|
Galena in Table 5 reveals also some impurities as traces in Pb site. At Dure, Fe.001 and Zn.001–.003 in the main stage are recorded in pyrite, while in the late stage, Fe.003–.29, Zn.047–.173, and Cd.003–.005 as traces in Pb site of pyrite are recorded.
At Lefan, galena has traces of Zn.011–.081, Fe.001–.002, and Cd.004 in the only main stage. No galena is recorded at Sinjar.
Generally, fluid inclusion and stable isotope data constrain the different stages of the rock evolution .
5.1. Fluid inclusions
Most fluid inclusions are essentially composed of a liquid phase and/or a vapor bubble, but they may also contain soluble salts and slightly ore elements.
In Table 7 , the homogenization temperatures are measured for 22 fluid inclusions in sphalerite, dolomite, and calcite minerals from the Dure deposits and 13 fluid inclusions in dolomite and calcite minerals from the Lefan deposits are given. This is helpful to constrain the hydrothermal fluid conditions during the formation of these deposits and to find out evidence of boiling. No suitable sample has been examined from Sinjar deposit for analysis .
The Dure deposit contains two phases of fluid inclusions at room temperature. They are H2O-rich liquid with H2O vapor bubbles constituting typically 5–10% vapor volume.
Primary fluid inclusions occur as single or clustered rounded or irregular shape inclusions that are ranging in size from 5 μm to < 10 μm ( Figure 4A ). Negative crystal forms are uncommon. Few primary inclusions have vapor volumes greater than 15% ( Figure 4A ). Secondary fluid inclusions occur as fracture-controlled planar groups, and they are thin, elongated, and irregular in shape ( Figure 4B ). The inclusions are <5 μm in size.
At room temperature, the Lefan deposit contains liquid-rich and vapor-rich fluid inclusions. The fluid inclusions typically contain H2O-rich liquid with H2O vapor bubbles. Some fluid inclusions contain CO2 vapor. Vapor-rich inclusions are subrounded or irregularly shaped and occur as clusters containing one to three inclusions ( Figure 4C ). These inclusions are larger in size, 5–12 μm, than the liquid-rich inclusions, <5μm.
Primary fluid inclusions are irregular or rounded and randomly distributed in carbonate minerals ( Figure 4D ). Secondary fluid inclusions form as planar groups of elongated inclusions ( Figure 4E ). The presence of fluid inclusions with variable liquid to vapor volumetric phase ratios is the most common evidence of entrapment from boiling fluids . The vapor-rich inclusions are believed to result from boiling fluids rather than necking-down processes ( Figure 4F ) due to their large size relative to the liquid-rich inclusions. There are absence of one-phase liquid inclusions and the presence of fluid-rich inclusions with relatively constant liquid:vapor phase ratios and consistent Th. The occurrence of vapor-rich and liquid-rich inclusions suggests the presence of two immiscible phases due to boiling at the time that the fluid inclusions were trapped. Textures indicative of boiling are present in the Lefan deposit, but are not as common as those cited in other epithermal systems (e.g., Dure section).
5.2. Microthermometric analysis
Microthermometric analyses have been carried out on fluid inclusions in sphalerite, dolomites, and calcites to obtain a preliminary estimate of the temperatures and salinities of the ore-bearing fluid. The results of the microthermometric analyses are summarized in Table 7 . Suitable fluid inclusions are observed only in saddle dolomite and calcite. Few suitable fluid inclusions are identified in sphalerite, where the observed inclusions are either too small for microthermometric measurement or they are judged to be secondary ( Figure 4A ).
Most inclusions chosen for analyses are considered as primary (contemporaneous with their host minerals) and closely related spatially and genetically to the sulfide mineralization. These inclusions are generally small (about 5 μm) and contain no daughter minerals ( Figure 4 A, C, and D). Due to the small size of the inclusions, proving accurate geothermometry is difficult. In addition, some hydrocarbon-rich fluid inclusions are also found in gangue minerals. Fluid inclusions in the late-generated barite within Bekhme formation at Lefan lead-zinc deposit are considered as fingerprint of hydrocarbon generation .
Salinities of fluid inclusions are determined by measuring the freezing temperatures of the fluid inclusions. According to Bodnar and Vityk , the freezing point of a fluid inclusion is the temperature at which the last ice crystal melts (ice melting temperature). The equation used to determine the salinity of a fluid inclusion is based on the H2O-NaCI system following Bodnar and Vityk .
where salinity = the weight percent (wt %) NaCl in solution and θ = freezing point depression (ice melting temperature) in °C. Freezing temperatures were measured prior to homogenization temperatures to avoid leakage or decrepitation of the fluid inclusions .
The salinities of the fluid inclusions in Dure deposit range from 13.93 to >23 wt% NaCl equivalent, whereas in the Lefan deposit they range from 3.06 to 14.57 wt% NaCl equivalent ( Table 7 ).
Homogenization temperatures were determined for primary and secondary inclusions with constant liquid:vapor volumetric phase ratios to avoid inaccurate measurements that could result from necking-down processes, leakage, stretching and decrepitation . Homogenization temperatures of the fluid inclusions in Dure deposit range from 45°C to 183°C, whereas the Lefan deposit has fluid inclusions that homogenize at temperatures ranging from 68°C to 284oC ( Table 7 ).
Both Dure and Lefan deposits have relatively some differences in fluid inclusion homogenization temperatures. The primary fluid inclusions in the Dure and Lefan deposits yielded homogenization temperatures with an average value of 130.4°C and 198°C, respectively, although values range from approximately 60°C to 284°C for both sections ( Table 7 ).
5.3. Interpretation of fluid inclusion results
The homogenization temperatures and salinities obtained for fluid inclusions in the present study are nearly similar to those reported for lead-zinc deposits of Mississippi Valley Type (MVT). Many authors such as Leach and Sangster , Paradis et al. , and Leach et al. [16, 17] have given the fluid inclusion temperatures in MVT deposits to range from about 50°C to 250°C; however, most of the measured temperatures were between 75°C and 200°C. The salinities of MVT fluids determined by those authors from fluid inclusions are typically 10–30 wt.% NaCl equivalent.
Both primary and secondary fluid inclusions of the deposits at Dure area contain the lowest Th values when compared to those of the Lefan area. The Lefan deposits have some vapor-rich fluid inclusions homogenized at relatively higher temperatures (200–280°C). These anomalous high temperatures can probably attributed to a vapor-rich fluid that trapped some liquid during boiling. During crystallization of sphalerite, the high temperature was preceded, but relatively moderate formation temperatures during the formation of saddle dolomite followed by cooling to about 50°C for late calcite formation. This supports the hypothesis of dilution and cooling of the transmitted fluids in the cracks and fissures of the host rocks by mixing with meteoric waters during later formed sulfides or perhaps post-sulfide calcite stages of deposition.
The diagram of salinity versus homogenization temperature of the fluid inclusions in the studied sections reveals no limit relationship ( Figure 5 ), but rather scattered between inclusion salinities and homogenization temperatures. This may be due to mixing of two different solutions; one was hot and saline, and the other was cool with low salinity (e.g., Taylor et al. ) as in Lefan section. Furthermore, invariant salinities of inclusions are interpreted as evidence of precipitation from a single fluid , as in Dure section.
Accordingly, the mineralization of the studied sulfides is seen to follow the type of MVT mineralization. However, the similarities between MVT inclusion fluids and oil-field brines are established to a wide acceptance of a basin-generated origin for MVT fluids. The high salinity is explained by the dissolution of evaporites, incorporation of connate bittern brines, or through infiltration of evaporated surface waters of the sedimentary basin brines [16, 17, 20].
5.4. Genesis of sulfides from stable isotopes
The average values of δ34S‰ of the studied sulfide of Dure, Lefan, and Sinjar are (0.8, 1.8, and 30.8‰), respectively. Sulfur isotope analysis shows that the sulfur in Dure and Lefan is originated from a mixture of various sources, but probably derived from seawater dissolved sulfate and/or diagenetic pyrite for Sinjar deposits. The δ13C and δ18O values of carbonate-host rocks are in the range of marine carbonates. Petrographic evidence and stable isotope data with fluid inclusions suggest that lead-zinc mineralization was caused by deeply circulating mineralizing fluids of high temperature (brines) within the source basin of deposition or due to tectonic processes, which possibly contribute in leaching metals from either the diagenetic host rocks or dewatering of deeper buried siliciclastic beds. The studied carbonate-hosted lead-zinc deposits seem to have many similarities with Mississippi Valley Type (MVT) deposit.
The values of sulfur isotope in the Dure (average = 0.8‰) and Lefan (average = 1.8‰) ( Table 8 ) cannot be attributed necessarily to a magmatic source of sulfur because the field observations together with ore microscopy provide no magmatic activity. The negative shift of δ34S value is resulted from seawater sulfates, or bacterial reduction, but possibly some sulfur could be derived due to the dissolution and leaching of preexisting sulfide-bearing igneous rocks.
The positive δ34S values suggest that sulfur was derived from seawater or ancient evaporates and connate water undergone subsequent reduction by ferrous iron or organic compounds  (see Figure 6 for more details). Perhaps seawater became enriched in light isotope by leached sulfur from deeper lithologic units during water circulation [23, 24, 25]. The influence of the enrichment of light sulfur isotopes is more significant for the Dure deposits (average, 0.8‰) than that for Lefan (average, 1.8‰).
Several evidences suggest the basinal brines source for hydrothermal fluids in the studied sections that are responsible for ore formation: first, the salinities and temperatures of the fluid inclusions of these deposits are mainly within the range of fluids of the MVT deposits [16, 17]; Second, the similarity in composition between the ore deposits and the most basinal brines. Low and narrow variation in δ34S values of sulfides ( Table 9 ) may indicate a single source of sulfur. Because of the absence of magmatic activity, it is realistic to consider the rocks in the basin of the studied sections as the source of sulfur. This leads to accept the positive δ34S, the organic sulfur enrichment in the beds of slightly positive to negative δ34S, and the presence of diagenetic pyrite in sedimentary rocks. Third, carbon and oxygen isotope values in the carbonate-host rocks are generally of relatively lower δ18O and higher δ13C. These values require involvement of marine carbonates and organic matter in the basin to supply such carbon and oxygen ( Figure 7 ). Moreover, there is a fact about the presence of hydrocarbon-rich fluid inclusions in some gangue minerals, and a late generation of barite , all supporting the probable basinal brines as the source of ore-forming fluids. As compared with typical basinal brines, some fluid inclusions in the present studied samples exhibit relatively lower salinities (<10 wt.% NaCl equiv.). The low salinity of these fluid inclusions shows a positive correlation with their Th content, possibly due to mixing between meteoric water and basinal brines.
The geochemical prospect throughout the recognition, characterization, fluid inclusions, and stable isotopes of the studied ore deposits carried out in this study emphasizes the suggestion that the Pb-Zn-Fe mineralization is concentrated from brines (marine waters). It is thought that the circulation of hydrothermal water happened at depths, where cracks and faults were formed at the beginning of the orogeny event. At that depth, the fluid was heated enough to dissolve metals from their hosting rocks during its ascent, and as the transported metal ions concentrated sufficiently, deposition took place. This process, together with permeability of the wall rock, is thought to be the eventual controlling factor of mineralization and the present geometry of the ore bodies and the alteration. Mineralization tends to occur in fractures and solution-collapse features formed during uplift of platform-carbonate sequences accompanying plate convergence. Therefore, the preferred genetic model for the concentration of ore metals at the studied carbonate rocks should involve basin dewatering due to compaction and regional tectonism and expulsion of the basin-derived fluids into the brecciated, karstificated, and highly porous recrystallized and dolomitized host rocks of the Kurra Chine and Bekhme formations.
The authors would like to thank the Earth Science Department, College of Science, Mosul University, for supplying available facilities and administrative support. A special thank goes to Dr Dave Alderton from Royal Holloway, London University, for his help in XRD; Prof. Dr Ahmet Gokce, Cumhuriyet University, Turkey; and Mrs Soheila Aghajani, Iran Mineral Processing Research Center (IMPRC) for their contribution to the fluid inclusion analysis. Considerable gratitude goes to NERC Isotope Community Support Facility, SUERC, Glasgow, Scotland, for sulfur isotope analysis, and to University-College London UCL, UK, for support in electron microprobe analysis (EMPA).