Water in Rocks and Minerals – Species, Distributions, and Temperature Dependences

The present book is a definitive review in the field of Infrared (IR) and Near Infrared (NIR) Spectroscopies, which are powerful, non invasive imaging techniques. This book brings together multidisciplinary chapters written by leading authorities in the area. The book provides a thorough overview of progress in the field of applications of IR and NIR spectroscopy in Materials Science, Engineering and Technology. Through a presentation of diverse applications, this book aims at bridging various disciplines and provides a platform for collaborations among scientists.


Introduction
Water is ubiquitously distributed in the interior of the earth, as various forms in rocks and minerals: In rocks, aggregates of minerals, fluid water in which molecular H 2 O is clustered, is trapped at intergranular regions and as fluid inclusions (e.g., Hiraga et al., 2001). In minerals, water is located as the form of -OH in their crystal structures as impurities. Surprisingly, such water species are distributed over five times in the earth's interior than ocean water (e.g., Jacobsen & Van der Lee, 2006), and play very important roles on earth dynamics such as deformation and reactions of minerals and rocks (e.g., Thompson & Rubie, 1985;Dysthe & Wogelius, 2006). In the filed of earth sciences therefore, people are trying to measure properties of water in rocks and minerals such as species, contents, distribution, thermal behaviour, migration rate, etc. Infrared (IR) spectroscopy is a powerful tool to quantitatively measure these properties of water in rocks and minerals (See Aines & Rossman, 1984;Keppler & Smyth, 2006 for IR spectra of various rocks and minerals). In this chapter, for an advanced IR spectroscopic measurement, I introduce in-situ high temperature IR spectroscopy to investigate above matters. First, I use chalcedonic quartz, which contains fluid water at intergranular regions and -OH in quartz crystal structures. Next, I use beryl, a typical cyclosilicate which contains isolated (not clustered) H 2 O molecules in open cavities of the crystal structure. Changes of the states of water in chalcedonic quartz and beryl by temperature changes and dehydration will be discussed. Finally, I perform two-dimensional IR mappings for naturally deformed rocks to investigate water distribution in polymineralic mixtures, and discuss possible water transportation during rock deformation.

Methods
Transmitted IR spectra for rocks and minerals are generally measured by making thin sections of samples with thicknesses of from 20 to 200 ǚm, which depend on concentrations and absorption coefficients based on Beer-Lambert law. A Fourier Transform IR microspectrometer totally used in this study is equipped with a silicon carbide (globar) IR source and a Ge-coated KBr beamsplitter. IR light through a sample is measured using a mercury-cadmium-telluride detector. temperature, and spectra were collected at about 1 minute. Mapping measurements were carried out using an auto XY-stage under atomospheric condition.

Water in rocks: As an example of chalcedonic quartz
Fluid water and -OH are trapped in chalcedonic quartz, an aggregate of microcrystalline quartz (SiO 2 ) grains (sometimes called as chalcedony or agate which has different transparency and is treated as a gem). Fluid water in chalcedonic quartz is dominantly trapped at intergranular regions such as grain boundaries and triple junctions of grains. IR spectra of chalcedonic quartz have been measured at room temperature (RT) (Frondel, 1982;Graetsch et al., 1985). In this section, I measure in-situ high temperature IR spectra for chalcedonic quartz as a representative material that abundantly contains fluid water and structurally-trapped -OH.

Typical IR spectrum at RT and water species
Figure 1 is a typical IR spectrum at RT for a thin section (ca. 100 ǚm thickness) of chalcedonic quartz. The band due to fluid water shows an asymmetric broad band ranging from 2750 to 3800 cm -1 with a shoulder around 3260 cm -1 : this band feature is the same with that of simple fluid water which exists everywhere around us (e.g., Eisenberg & Kauzman, 1969). -OH in chalcedonic quartz is mainly trapped as Si-OH by breaking the network of SiO 2 bonds (Kronenberg & Wolf, 1990), and the OH stretching band is sharp (3585 cm -1 at RT). The bending mode of fluid water, which should be seen at around 1600 cm -1 , is hindered by many sharp Si-O stretching bands. Combination modes of the stretching and bending modes of fluid water and Si-OH are clearly seen for a thicker sample (1 mm in Fig.  1), and they are detected at 5200 cm -1 and 4500 cm -1 respectively. Contents of fluid water and Si-OH can be calculated from these bands' heights using their molar absorption coefficients of 0.761 and 1.141 L mol -1 cm -1 , respectively (Scholze, 1960;Graetsch et al., 1985); in this case 0.32 wt % H 2 O and 0.28 wt % Si-OH, respectively (Fukuda et al., 2009a). Fig. 1. Typical IR spectrum of chalcedonic quartz at RT. The sample thickness of 100 ǚm for 4000-1000 cm −1 and 1 mm for 5500-4000 cm −1 (combination modes of the stretching and bending modes of fluid water and Si-OH).

Water vibrations at high temperatures
High temperature IR spectra were measured for the sample set on the heating stage (Fig. 2). With increasing temperature up to 400 °C, the broad band due to fluid water dominantly and asymmetrically shifts to high wavenumbers. Contrary to this, the band due to Si-OH slightly shifts to high wavenumbers. After quenching to RT from high temperatures, these water bands do not change from those before heating, indicating that vibrational states of fluid water and Si-OH are changed at high temperatures without dehydration. The following is discussion for changes in the vibrational states of water. Fig. 2. In-situ high temperature IR spectra of a chalcedonic quartz (black lines) in the water stretching region (Replotted from Fukuda et al., 2009c). The spectrum at RT after heating at 400 °C is shown as gray line on the top, showing no significant change from the spectrum before heating.
Since vibrational energy of OH stretching of Si-OH is structurally limited within quartz crystal structures, the band is sharp even at high temperatures. The deviation of the wavenumber from free -OH stretching (around 3650 cm -1 ; summarized in Libowitzky, 1999) can be explained by the work of hydrogen bond in Si-OH…O-Si in quartz crystal structures, which weaken OH vibrational energy. With increasing temperature, the hydrogen bond distance is extended due to thermal expansion of quartz crystal structure (e.g., Kihara, 2001). Resultantly, the band due to Si-OH slightly shifts to high wavenumber and the band height is not so decreased (3599 cm -1 at 400 °C; Fukuda & Nakashima, 2008).
In fluid water, H 2 O is clustered and networked by various hydrogen bond strengths (e.g., Brubach et al., 2005). Therefore, fluid water shows the broad band. With increasing temperatures, the average coordination numbers of a H 2 O molecule to adjacent H 2 O molecules at confined intergranular regions of chalcedonic quartz are reduced due to increases of vibrational energies without dehydration. The average coordination number of a single H 2 O molecule in fluid water is 2-3 molecules at RT (Brubach et al., 2005), and 1-2 above supercritical temperature (Nakahara et al., 2001). This leads to significant shifts of wavenumbers to higher. Also, band heights of fluid water are decreased with increasing www.intechopen.com temperatures. For example, the maximum band height at 400 °C is approximately 50 % of that at RT. This is also because of decreases of average numbers of H 2 O in areas that IR light captures (i.e., density; Schwarzer et al., 2005).

Dehydration behaviour
When the sample is kept at high temperatures, dehydration occurs. High temperature IR spectra were continuously measured to monitor dehydration. Figure 3 shows dehydration behaviour measured at 500 °C (Fig. 3a) and 400 °C (Fig. 3b). Both of the experiments were performed by heating during 500 minutes in total. Broad bands around 3800-3000 cm -1 in both spectra decrease with keeping at high temperatures, and the wavenumbers of the broad bands are not changed during heating. IR spectra at RT after heating (gray spectra in Fig. 3) also show decreases of fluid water. This indicates that fluid water was dehydrated through intergranular regions which are fast paths for mass transfers (See Ingrin et al., 1995;Okumura and Nakashima, 2004;Fukuda et al., 2009c for estimation of water diffusivity). Over 50 % of the band areas are decreased during the heating in 84 minutes at 500 °C. Band areas of 80 % are decreased in 250 minutes, and the features of the spectra are not changed after that. The RT temperature spectrum after 500 minutes heating at 500 °C also shows significant reduction of board band due to fluid water. This remained band due to fluid water may reflect fluid inclusions, which is tightly trapped at open spaces in crystal structures. On the other hand, 60 % of the band areas are preserved after heating in 500 minutes at 400 °C, and the RT spectrum after 500 minutes heating at 400 °C still shows a strong signal of fluid water. Fig. 3. Dehydration behaviour at 500 °C (left) and 400 °C (right) in the water stretching region (after Fukuda et al., 2009c). The spectra at RT after heatings are also shown as gray lines. The integrated heating times are shown at the right of each spectrum.
Since contents of fluid water are reduced by dehydration, different degrees of hydrogen bonds of Si-OH at intergranular regions (surface silanol) to fluid water are formed. This leads to the appearances of several -OH bands (3660 and 3730 cm -1 at 500 °C, and possibly the split of the band at 3585 cm -1 at RT) (Yamagishi et al., 1997). The appearance of the band at 3730 cm -1 at 0 minute heating at 500 °C is due to slight dehydration during heating from RT to 500 °C at 100 °C/minute. The wavenumbers of these new -OH bands at high temperature are slightly different from those at RT, presumably due to thermal expansions of crystals and changes of hydrogen bond distances at high temperature.

H 2 O molecules in minerals: As an example of beryl
In addition to fluid water in rocks and -OH in mineral crystal structures as described above, isolated (not clustered) H 2 O molecules are incorporated in open cavities of crystal structures, and they are sometimes coupled with cations. H 2 O in open cavities has well been studied for beryl, a typical cyclosilicate (after Wood & Nassau, 1967). Ideal chemical formula of beryl is Be 3 Al 2 Si 6 O 18 , and six-membered SiO 4 rings are stacked along the crystallographic c-axis and make a pipe-like cavity called a channel ( Fig. 4) (Gibbs et al., 1968). Isolated H 2 O is trapped in the channel, and forms two kinds of orientations, depending on whether it coordinates to a cation (called type II) or not (called type I) (after Wood & Nassau, 1967). Such cations are trapped in the channels to compensate the electrical charge balances caused by Be 2+ -Li + and Si 4+ -Al 3+ substitutions and lacks of Be 2+ in the crystal structure of beryl. The cations in the channels are assumed to be mainly Na + , and some other alkali cations may be incorporated (Hawthorne and Černý, 1977;Aurisicchio et al., 1988;Artioli et al., 1993;Andersson, 2006). In this section, I introduce polarized IR spectra of beryl, and discuss changes of the states of type I/II H 2 O in the channels by temperature changes and dehydration.

Chemical composition of the sample
The chemical composition of the natural beryl sample used in this study was analyzed by Xray wavelength dispersive spectroscopy for major atomic contents, inductivity coupled plasma-atomic emission spectroscopy for Be content, and atomic absorption spectroscopy for Li and Rb contents ( Table 1). The type I/II H 2 O contents were determined from intensities of IR bands due to the asymmetric stretching of type I and the symmetric stretching of type II in a polarized IR spectrum at RT (See the spectrum in the next section), using their molar absorption coefficients of 206 L mol -1 cm -1 and 256 L mol -1 cm -1 , respectively (Goldman et al., 1977). The CO 2 content was also calculated for the band at 2360 cm -1 from 800 L mol -1 cm -1 in Della Ventura et al. (2009). In the chemical composition, the Li and Na contents are relatively high in addition to the Si, Al and Be contents of major atoms. Be content (2.893 in 18 oxygen), which is lower than the ideal composition of beryl (Be 3 Al 2 Si 6 O 18 ), must be replaced by Li, and Na must be incorporated as Na + in the channels to compensate the electrical charge balance. However, Li + may be also incorporated in the channels, since the Li content is not completely explained by Be 2+ -Li + substitution (e.g., Hawthorne and Černý, 1977). Table 1. Chemical composition of the beryl sample used in this study.

Typical polarized IR spectra of beryl at RT and types of H 2 O
Polarized IR spectra were measured by inserting a wire grid IR polarizer to IR light through the sample. Electric vector of IR light, E to the c-axis (i.e., the direction of the arraignments of the channels) were gradually changed and spectra were obtained (Fig. 5). Fundamental vibrations of type I/II H 2 O (asymmetric stretching; Ǜ 3 , symmetric stretching; Ǜ 1 , and bending modes; Ǜ 2 ) can be detected under different polarized conditions, which correspond to the orientations of type I/II H 2 O in the channels (Fig. 4) and IR active orientations of their vibrational modes: In a sample section of the (100)-plane (i.e., the section including the alignment of channels), the bands due to the Ǜ 3 mode of type I (referred to as Ǜ 3 -I hereafter), Ǜ 1 -II, and Ǜ 2 -II are dominantly detected under E//c-axis (Fig. 5a). Their wavenumbers are 3698, 3597, and 1628 cm -1 , respectively.
Under Ec-axis in the (100)-section (bottom spectra in Fig. 5a) or in the (001)-section (Fig. 5b), the bands due to Ǜ 3 -II (3661 cm -1 ), Ǜ 1 -I (3605 cm -1 ), and Ǜ 2 -I are dominant. The Ǜ 2 -I www.intechopen.com somewhat shows three bands at 1640, 1600, and 1546 cm -1 (e.g., Wood & Nassau 1967;Charoy et al., 1996;Łodziński et al., 2005), and I refer these three bands to the Ǜ 2 -I related bands. The asymmetric stretching mode of CO 2 molecules is detected at 2360 cm -1 under Ec-axis. These H 2 O and CO 2 bands are not changed at any angles of E to the sample in the (001)-plane, corresponding to that these molecules are isotropically distributed due to the hexagonal symmetry of beryl. There are other unassigned bands; for example the sharp band at 3594 cm -1 can be seen. This band has been argued and might be due to Na + -OH in the channels.
Ideally, the Ǜ 3 , Ǜ 1 , and Ǜ 2 modes of isolated free H 2 O are detected at 3756, 3657, and 1595 cm -1 , respectively at RT (Eisenberg & Kauzman, 1969). That the fundamental vibrations of type I/II H 2 O in beryl are deviated from those for ideal value, is due to interaction of type I/II H 2 O with channel oxygens and cations (Fig. 5). The wavenumbers of the stretching modes of type I/II H 2 O at RT are lower than those of free H 2 O, while those of the bending modes are higher. Falk (1984) experimentally demonstrated reverse correlations of band shifts between stretching and bending modes. The lower wavenumbers of the stretching modes than those of isolated water molecules are due to weak hydrogen bonds between type I/II and channel oxygens, similarly to the case for chalcedonic quartz. The reverse wavenumber shifts from ideal H 2 O between stretching and bending modes is mainly explained by changes in H-H repulsion constants in a simple spring model (Fukuda & Shinoda, 2008).

Water vibrations at high temperatures
Significant dehydration does not occur during short time heating from RT to 800 °C (temperature raise of 100 °C/minute and 1 minute for the measurements at each temperature; see Section 2). Figure 6 shows high temperature behaviour of type I/II H 2 O in beryl under E//c-axis (Fig. 6a) and Ec-axis (Fig. 6b) in the water stretching and bending regions. Spectral changes are different for each vibrational mode of type I/II H 2 O: Under E//c-axis at RT, the Ǜ 3 -I and Ǜ 1 -II bands are clearly seen at 3698 and 3597 cm -1 , respectively. The Ǜ 3 -I band is rapidly decreased in its height with increasing temperature; for example 60 % of the band height decreases at 200 °C, compared with that at RT (Fig. 7). The rapid decreases of the type I band are also seen for the Ǜ 1 -I band and the Ǜ 2 -I related bands under Ec-axis (Fig. 6b). Contrary to the case for the type I bands, only 20 % of the Ǜ 1 -II and Ǜ 2 -II bands are decreased at 200 °C. Alternatively, wavenumber shifts dominantly occur for these bands. The wavenumber of the former (3597 cm -1 at RT) and latter bands (1628 cm -1 at RT) linearly shift to lower and higher, with increasing temperature (Fig. 7). The changes of the Ǜ 3 -II band (3661 cm -1 at RT) under Ec-axis are difficult to monitor because of overlapping with other bands at high temperatures. Since these changes are reversible upon heating and cooling, they are not due to dehydration but changes of the states of type I/II H 2 O in the channels. Discussion is as follows. Fig. 7. Changes of band heights (left) and wavenumbers (right) of the Ǜ 3 -I, Ǜ 1 -II, and Ǜ 2 -II bands with increasing temperature (Modified after Fukuda & Shinoda, 2011). Values are determined from the spectra in Fig. 6a.
These changes in band heights and wavenumbers of type I/II H 2 O are interpreted mainly due to the presence (type I) or absence of cations (type II) in the beryl channels (Fig. 4). Since type I H 2 O is not coupled with a cation, its position in the channels is easy lost with increasing temperature, resulting the rapid decreases of band heights. On the other hand, since the position of type II H 2 O is fixed by a cation (mainly Na + ), the decreases in band heights with increasing temperature do not significantly occur, compared with those for type I bands. Alternatively, the wavenumber shifts occur. The inverse wavenumber shifts of type II bands in stretching and bending modes would be due to modifications in vibrational constants in the thermally-expanded beryl channels (Fukuda et al., 2009b), as similar to the deviations of wavenumbers from ideal H 2 O molecule in RT spectra (Section 4.2). www.intechopen.com

Dehydration behaviour
The beryl sample was heated on the heating stage at 850 °C where dehydration is enhanced (Fukuda & Shinoda, 2008). Polarized IR spectra are shown only at RT quenched from 850 °C (Fig. 8), since in-situ high temperature IR spectra at 850 °C show broadened water bands (Fig. 6) and changes of each bands are not clearly monitored. Under E//c-axis, the Ǜ 3 -I band at 3698 cm -1 disappeared at heating of 12 hours, without any wavenumber changes (Fig. 8a). This trend is same with the band at 3605 cm -1 (Ǜ 1 -I) and three Ǜ 2 -I-related bands under Ecaxis (Fig. 8b). Some bands remain in the water bending region under Ec-axis, and they would be due to structural vibrations of beryl. The dehydration behaviour of type II bands are different with that of type I: Since the position of type II H 2 O is fixed by a cation, its dehydration is obviously slower than type I H 2 O. Under E//c-axis, new bands develop at 3587 and 1638 cm -1 with decreasing of the initial bands at 3597 (Ǜ 1 -II) and 1628 cm -1 (Ǜ 2 -II). The band at 3661 cm -1 (Ǜ 3 -II) under Ec-axis also shows the wavenumber shifts to the lower with decreasing its intensity. These bands are stable after 24 hours heating. The appearances of these bands are explained as follows. A cation is coordinated by one or two type II H 2 O due to a spatial restriction of the channel (Fig. 4). Therefore, the dominant band at 3597 (Ǜ 1 -II) and 1628 cm -1 (Ǜ 2 -II) before heating would be mainly due to doubly-coordinated type II to a cation, mainly Na + . Since type II H 2 O dehydrates by heating, singly-coordinated type II are created. The wavenumbers of singlyand doubly-coordinated H 2 O have been calculated for free H 2 O molecules. According to a numerical approach for water vibrations by Bauschlicher et al. (1991), the wavenumbers of H 2 O-Na + -H 2 O is higher in its stretching modes and lower in the bending modes than those of Na + -H 2 O in approximately 10 cm -1 . This is consistent with wavenumber shifts in beryl due to the formation of singly-coordinated type II at 3587 (Ǜ 1 -II) and 1638 cm -1 (Ǜ 2 -II).
Another possibility for the wavenumber shifts of the Ǜ 1 -II and Ǜ 2 -II bands is the presence of Li + in the channels. According to the calculation in Lee et al. (2004) for free H 2 O molecules, the wavenumbers of Li + -H 2 O is higher in its stretching modes and lower in the bending modes than those of Na + -H 2 O. Also, binding energy of Li + to H 2 O is higher than that of Na + to H 2 O, which indicates the stable stability of Li + -H 2 O during dehydration. If Li + is trapped in the beryl channels, it can cause the wavenumber shifts observed in this study.
A sharp and unassigned band is seen at 3594 cm -1 under Ec-axis. This band is also more stable than that for type I bands. The wavenumber of this band is different from any vibrational modes of type I/II H 2 O. Judging from the thermal stability and the wavenumber, this band may be related to Na + -OH in beryl, as its presence has been argued in Andersson (2006).

IR mapping measurements for deformed rocks
Rocks are deformed at shear zones in the interior of the earth. Rocks, which underwent brittle and plastic deformation at shear zones, are called as cataclasites and mylonites, respectively. Brittle deformation of continental crusts (mainly granitoids) is dominated from the ground to 10-20 km depth. Plastic deformation of rocks is dominated below that with increasing temperature and pressure. Another important factor that significantly contributes to plastic deformation of rocks is water. Water contents in ppm order dramatically promote plastic deformation of minerals, as confirmed by deformation experiments (e.g., Griggs, 1967;Jaoul et al., 1984;Post & Tullis, 1998;Dimanov et al., 1999). Also, water contributes to solution-precipitation which sometimes involves reactions among minerals (especially, feldspar and mica in granitoids) (e.g., summarized in Thompson & Rubie, 1985;Dysthe & Wogelius, 2006). Then, solution-precipitation creep may also contribute to the strength of the crusts (Wintsch & Yi, 2002;Kenis et al., 2005). Thus, water contents and distribution as well as its species are important for rock deformation.
In this section, I use IR spectroscopy to map two-dimensional water distributions as well as to consider its species in deformed granites. I especially focus on water distributions associated with solution-precipitation process of feldspar, and consider possible transport mechanisms of water.

Samples and analyses
Deformed granites were collected from outcrops in an inner shear zone of the Ryoke Metamorphic Belt in the Kishiwada district, Osaka Prefecture, SW Japan, and believed to be www.intechopen.com deformed at ~500 °C (Takagi, 1988;Imon et al., 2002;. Sample thin sections of ~50 ǚm were at first observed under a polarized optical microscope and a back-scattered electron (BSE) image which reflects compositional differences in a scanning electron microscope (SEM). After IR mapping measurements, thin sections were again polished to suitable thickness (~20 ǚm) to observe detailed microstructures under the optical microscope.
IR mapping measurements were carried out along ~1000 ǚm traverses with 30 ǚm spatial resolution (aperture size) in steps of 30 ǚm. See Section 2 for the instrument of IR spectroscopy. The integral absorbances of the water stretching bands in the range 3800-2750 cm -1 are displayed as a color-contoured image for a measured sample area. Color-contoured images can be used as a qualitative representation of the distribution of water, since absorption coefficients tend to increase linearly with decreasing wavenumbers (Paterson, 1982;Libowitzky & Rossman, 1997). When the absolute water contents of the minerals are to be determined, Beer-Lambert law is applied, using the absorption coefficients for each mineral. For K-feldspar and plagioclase, I used the absorption coefficients of integral water stretching bands reported by Johnson & Rossman (2003) (15.3 ppm -1 cm -2 ), and for quartz, those reported by Kats (1962). Kats (1962) reported following relation between water content in quartz and integral absorbance of water stretching bands; C(H/10 6 Si)=0.812 x A int /d, where A int is the integral absorbance and d is the sample thickness in cm. Then, I converted H/10 6 Si value to a ppm H 2 O unit (1 ppm = 6.67 H/10 6 Si), as also adopted in Gleason & DeSisto (2008). To distinguish Si-OH and H 2 O contents separately, their combination bands of the stretching and bending modes should be used, as shown in Section 3. However, it is difficult for these samples, since sample thicknesses are thin for texture observations under the optical microscope, and 1 mm thickness is needed to measure the combination bands.

Typical water distribution in deformed granite
At first, I introduce water distribution in the granite mylonite with typical microtexture (Fig.  9) (See Passchier & Trouw, 2005 for many textures of deformed rocks). As can be seen under the polarized optical microscope (Fig. 9a), quartz is recrystallized by subgrain rotation, and plastically deformed by dislocation creep. Quartz grains are elongated with the aspect ratio of ca. 3:1 and the long axis is ca. 250 ǚm. Feldspar is a relatively hard mineral in this deformation condition, is not plastically deformed, and behaves as rigid body sometimes with fracturing (i.e., brittle deformation). Such relatively hard minerals are called as porphyroclasts. Under the BSE image, rims of plagioclase are replaced by K-feldspar, which would be due to solution-precipitation with or without reaction called myrmekitization (e.g., Simpson & Wintsch, 1989). Myrmekitization is the following reaction; K-feldspar + Na + + Ca 2+ = plagioclase + quartz + K + , where cations are included in circulating fluid water. Water contents in these replaced K-feldspar are difficult to determine in this region because of the limitation of its distribution, and discussed for other regions later.
The IR spectra for both plagioclase and quartz show broad bands at 3800-2750 cm -1 , which is due to the stretching vibration of fluid water (Fig. 9d) (See Section 3). Fluid water must be trapped as fluid inclusions within both minerals, since spatial resolution of 30 ǚm (aperture size) covers intracrystalline regions, rather than intergranular regions. The IR spectra for the plagioclase porphyroclast also exhibit sharp bands at 3625 and 3700 cm -1 , which are due to the stretching vibrations of structural hydroxyl in plagioclase (e.g., Hofmeister & Rossman, 1985;Beran, 1987;Johnson & Rossman, 2003). The band at 1620 cm -1 in plagioclase is due to www.intechopen.com (c) Water distribution mapped by integral absorbance of water stretching bands in the 3800-2750 cm -1 range of the IR spectra. The color contours from black to red approximately correspond to water contents from low to high. The boundaries of minerals are shown as dotted lines. Arrows with letters show the locations used to illustrate the various selected IR spectra in (d). Pl; plagioclase, Qtz; quartz. the bending vibrations of fluid water. Other bands in the range of 2500-1500 cm -1 are due to the structural vibrations of plagioclase. Six sharp bands between 2000 and 1500 cm -1 for quartz are due to the structural vibrations of quartz, which are same with the spectra for chalcedonic quartz (Fig. 1). Recognition of the bending vibrations of fluid water in quartz is difficult because of these sharp structural bands. Water concentration in this plagioclase porphyroclast ranges from 200 to 700 ppm, with an average of 450 ppm, consistent with values reported in the literature (Hofmeister & Rossman, 1985;Beran, 1987;Johnson & Rossman, 2003). The heterogeneity of water distribution in plagioclase does not directly correspond to textures under the optical microscope and BSE. The amount of water in the quartz is much lower than that in the plagioclase, ranging from 80 to 300 ppm, with an average of 130 ppm. www.intechopen.com

Water distribution around feldspar fine grains and possible water transportation
Water distribution was measured for an area where fine-grained K-feldspar develops around K-feldspar and plagioclase porphyroclasts (Fig. 10a). The BSE image shows that finegrained K-feldspar regions, which are constructed by ~20 ǚm grains, contain patchy distribution of plagioclase (Fig. 10b). This indicates that solution-precipitation of K-feldspar, which may be accompanied with myrmekitization, occurred for the development of fine grains. The IR-mapped image shows that water contents in these regions are 220 ppm H 2 O in average; low and homogeneously distributed, although fluid water must be participated in the solution-precipitation process. The features of water stretching bands of fine-grained K-feldspar and K-feldspar porphyroclasts do not show structural -OH bands, differently from plagioclase (Fig. 10d); only broad bands can be seen at 3800-2750 cm -1 . Water contents in K-feldspar and plagioclase porphyroclasts are 200-1150 ppm; heterogeneously distributed compared with those in fine-grained K-feldspar regions.  shows water distribution in an area that dominantly includes fine-grained plagioclase. The fine-grained plagioclase develops around plagioclase porphyroclasts, and some of it is closely associated with K-feldspar under the BSE image (Fig. 11b). Quartz in this region can be identified from its characteristic structural vibrations in the IR spectra (Fig. 11d), indicating that myrmekitization (K-feldspar + Na + + Ca 2+ = plagioclase + quartz + K + ; see Section 5.2) occured during rocks deformation. Water contents in the area where fine-grained plagioclase grains are associated with small amounts of K-feldspar and quartz are roughly 2-4 times lower than those within plagioclase porphyroclasts, as inferred from the color contrasts in the IR mapping image (Fig. 11c). However, it is not possible to measure the absolute water contents in this area because of a mixture of plagioclase, Kfeldspar, and quartz; consequently, the absorption coefficients are not clear. (c) Water distribution mapped by integral absorbance of water stretching bands in the 3800-2750 cm -1 range of the IR spectra. The boundaries of minerals are shown as dotted lines. Arrows with letters show the locations used to illustrate the various selected IR spectra in (d). Pl; plagioclase, FGP; fine-grained plagioclase, Qtz; quartz. IR spectra show quartz vibrational bands in fine-grained plagioclase. Absolute water contents for fine-grained plagioclase are not determined due to the mixtures of quartz and K-feldspar.
In general, fluid water can be trapped at intergranular regions (grain boundaries) up to a few thousand ppm H 2 O, as reported for quartz aggregates whose each grain size is a few tens of micrometers to a few hundred micrometers (e.g., Nakashima et al., 1995;Muto et al., 2004;O'kane et al., 2005). In this study, intergranular regions must also be covered in the measurements for fine-grained K-feldspar-and plagioclase-dominant regions. The solution-precipitation process that produces fined-grained K-feldspar and plagioclase are subsequently and/or simultaneously enhanced by the ability of fluid water along intergranular regions to carry ions in solution, especially in situations where intergranular diffusion was promoted by an increase in surface area. (e.g., Simpson & Wintch, 1989;Fitz Gerald & Stünitz, 1993;Tsurumi et al., 2003). However, contrary to the previous knowledge on water contents at intergranular regions, water contents in fine-grained Kfeldspar-and plagioclase-dominant regions are low and homogeneous (av. 250 ppm). Therefore, it can be inferred that fluid water may not abundantly be trapped in newlycreated grains, and rather released during and/or after the solution-precipitation process. The release of fluid water and dissolved ions, which contributed to the process, was a result of the concentration gradients formed in the context of numerous newly-created intergranular regions within the mix of fine-grained feldspar and quartz. As a consequence, the entire process results in a positive feedback to promote the solutionprecipitation process.

Conclusions
I investigated high temperature behaviour of water in rocks and minerals. Chalcedonic quartz was used as a representative rock which contains abundant fluid water at intergranular regions and -OH in quartz crystal structures. The average coordination numbers of water molecules were degreased with increasing temperature, which causes shifts of stretching vibrations to higher wavenumbers. Dehydration of fluid water in the chalcedonic quartz was monitored by keeping at high temperatures. Fluid water was rapidly dehydrated through intergranular regions at 500 °C, and new hydroxyl bands appeared with dehydration of fluid water.
States of water molecules, which are not clustered like fluid water, were investigated for beryl, typical cyclosilicate, using high temperature polarized IR spectroscopy. The beryl channels, open cavities in the crystal structures, contain two types of water molecules which freely exist or coordinate to cations from up and/or below them. The former type of water easily looses its specific position, resulting the rapid degreases of its IR band heights without dehydration, and shows rapid dehydration at 850 °C. The latter type of water shows significant changes in its wavenumbers with increasing temperatures. There are slight modifications in the wavenumbers during dehydration due to changes of coordination to cations during dehydration.
Distribution of fluid water was measured for deformed granites. K-feldspar and plagioclase fine grains were formed around porphyroclasts by solution-precipitation process. Water contents in fine-grained K-feldspar-and plagioclase-dominant regions show low and homogeneous distribution of fluid water, while water distributions in host porphyroclasts were heterogeneous. This indicates that fluid water, which was involved in the solution-precipitation process, was released during and/or after the solutionprecipitation process. The present book is a definitive review in the field of Infrared (IR) and Near Infrared (NIR) Spectroscopies, which are powerful, non invasive imaging techniques. This book brings together multidisciplinary chapters written by leading authorities in the area. The book provides a thorough overview of progress in the field of applications of IR and NIR spectroscopy in Materials Science, Engineering and Technology. Through a presentation of diverse applications, this book aims at bridging various disciplines and provides a platform for collaborations among scientists.