Analysis of E||X-polarized optical absorption spectra of natural olivines of various origin in the range of electronic spin-allowed dd-transitions of Fe2+ evidences that in some crystals, there is a weak ordering of Fe2+ as in M1, as in M2 structural sites. The samples of three different depth facies seem showing a vague tendency of lowering of k D -values from spinel-pyroxene (Sp-Px) through graphite-pyrope (G-Py) to diamond-pyrope (D-Py) facies, but the statistics are too poor (24 samples only) to be certain of it. Weak relations between Mg, Fe2+-distribution and iron content were found for the samples of Sp-Px- and G-Py-facies, while there is practically no one for those of the deepest D-Py facie.

Mineral-specific IR absorption coefficients were calculated for natural and synthetic olivine, SiO 2 polymorphs, and GeO 2 with specific isolated OH point defects using quantitative data from independent techniques such as proton–proton scattering, confocal Raman spectroscopy, and secondary ion mass spectrometry. Moreover, we present a routine to detect OH traces in anisotropic minerals using Raman spectroscopy combined with the “Comparator Technique”. In case of olivine and the SiO 2 system, it turns out that the magnitude of ε for one structure is independent of the type of OH point defect and therewith the peak position (quartz ε = 89,000 ± 15,000 l mol_H_2O^-1 cm^-2 ), but it varies as a function of structure (coesite ε = 214,000 ± 14,000 l mol_H_2O^-1 cm^-2 ; stishovite ε = 485,000 ± 109,000 l mol_H_2O^-1 cm^-2 ). Evaluation of data from this study confirms that not using mineral-specific IR calibrations for the OH quantification in nominally anhydrous minerals leads to inaccurate estimations of OH concentrations, which constitute the basis for modeling the Earth’s deep water cycle.

Infrared spectroscopic data show that nominally anhydrous olivine (Mg,Fe)(2)SiO(4) contains traces of H(2)O, up to several hundred wt. ppm of H(2)O (Miller et al., 1987; Bell et al., 2004; Koch-Muller et al., 2006; Matsyuk & Langer, 2004) and therefore olivine is suggested to be a water carrier in the mantle (Thompson, 1992). Protonation of olivine during its crystallization from a hydrous melt resulted in the appearance of intrinsic OH-defects (Libowitsky & Beran, 1995). Mantle olivine nodules from kimberlites were investigated with FTIR and TEM methods (Khisina et al., 2001, 2002, 2008). The results are the following: (1) Water content in xenoliths is lower than water content in xenocrysts. From these data we concluded that kimberlite magma had been saturated by H(2)O, whereas adjacent mantle rocks had been crystallized from water-depleted melts. (2) Extrinsic water in olivine is represented by high-pressure phases, 10 angstrom-Phase Mg(3)Si(4)O(10)(OH)(2)center dot nH(2)O and hydrous olivine n(Mg,Fe)(2)SiO(4)center dot(H(2)MgSiO(4)), both of which belong to the group of Dense Hydrous Magnesium Silicates (DHMS), which were synthesized in laboratory high-pressure experiments (Prewitt & Downs, 1999). The DHMS were regarded as possible mineral carriers for H(2)O in the mantle; however, they were not found in natural material until quite recently. Our observations demonstrate the first finding of the 10 angstrom-Phase and hydrous olivine as a mantle substance. (3) 10 angstrom-Phase, which occurred as either nanoinclusions or narrow veins in olivine, is a ubiquitous nano-mineral of kimberlite and closely related to olivine. (4) There are two different mechanisms of the 10 angstrom-Phase formation: (a) purification of olivine from OH-bearing defects resulting in transformation of olivine to the 10 angstrom-Phase with the liberation of water fluid; and (b) replacement of olivine for the 10 angstrom-Phase due to hydrous metasomatism in the mantle in the presence of H(2)O fluid.

A series of uncommon micro- and nano-inclusions has been identified in diamonds from the Rio Soriso placer deposit in Mato Grosso State, Brazil. The micro- inclusions are variable in size, from 1 to 300 mu m. Usually, they are polymineralic, being formed predominantly by intergrowths of carbonates, silicates and other minerals. Carbonates are represented mostly by dolomite and occasionally by calcite. Silicates found are coesite, wollastonite-II, cuspidine and monticellite. Sulphides and ilmenite form micro-inclusions as well. Nano-inclusions are different from micro-inclusions not only in size (not exceeding 200 nm): they are usually included in micro-inclusions. Among nano-inclusions, halides (NaCl, KCl, CaCl(2) and PbCl(2)), anhydrite, spine], phlogopite, PbO(2), TiO(2) with an alpha-PbO(2) structure, native Fe, and other phases are identified. All these minerals are of the eclogitic association: they are either associated with coesite or are included in a diamond with a light, 'organic' carbon isotopic composition (with delta (13)C from -14 to -25 parts per thousand PDB). This confirms our earlier conclusion that diamonds from the Juina area may have formed as a result of subduction of the crustal material to depths of at least the lower transition zone or even the lower mantle. The pressure estimates for the investigated diamonds vary in a range from 3 to 10 GPa. An interesting assemblage of calcite + cuspidine + wollastonite + monticellite + fluid identified in one of the studied diamonds is considered as a product of a reaction of wollastonite + fluid forming cuspidine + monticellite. The presence of numerous pores, cavities and bubbles in mineral inclusions, and identification of an association of volatile-containing mineral inclusions, such as halides (NaCl, KCl, CaCl(2), and PbCl(2)), fluorine-containing silicate cuspidine, and phlogopite emphasize the important role of volatiles, particularly chlorine and fluorine in the formation of the diamonds. (C) 2009 Elsevier B.V. All rights reserved.

Nyerereite and nahcolite have been identified as micro-and nano-inclusions in diamond from the Juina area, Brazil. Alongside them are Sr- and Ba-bearing calcite minerals from the periclase-wustite series, wollastonite II (high), Ca-rich garnet, spinels, olivine, phlogopite and apatite. Minerals of the periclase-wustite series belong to two separate groups: wustite and Mg-wustite with Mg# = 1.9-15.3, and Fe-periclase and periclase with Mg# = 84.9-92.1. Wollastonite-II (high, with Ca:Si = 0.992) has a triclinic structure. Two types of spinel were distinguished among mineral inclusions in diamond: zoned magnesioferrite (with Mg# varying from 13.5-90.8, core to rim) and Fe spinel (magnetite). Olivine (Mg# = 93.6), intergrown with nyerereite, forms an elongate, lath-shaped crystal and most likely represents a retrograde transformation of ringwoodite or wadsleyite. All inclusions are composed of poly-mineralic solid mineral phases. Together with previously found halides, sulphates and other mineral inclusions in diamond from Juina, they form a carbonatitic-type mineral paragenesis in diamond which may have originated in the lower mantle and/or transition zone. Wustite inclusions with Mg# = 1.9-3.4, according to experimental data, may have formed in the lowermost mantle. The source for the observed carbonatitic-type mineral association in diamond is lower-mantle natrocarbonatitic magma. This magma may represent a juvenile mantle melt, or be the result of low-degree partial melting of deeply-subducted carbonated oceanic crust. This magma was rich in volatiles, such as Cl, F and H, which played an important role in the formation of diamond.

Mineral-specific IR absorption coefficients were calculated for natural and synthetic olivine, SiO2 polymorphs, and GeO2 with specific isolated OH point defects using quantitative data from independent techniques such as proton-proton scattering, confocal Raman spectroscopy, and secondary ion mass spectrometry. Moreover, we present a routine to detect OH traces in anisotropic minerals using Raman spectroscopy combined with the "Comparator Technique''. In case of olivine and the SiO2 system, it turns out that the magnitude of epsilon for one structure is independent of the type of OH point defect and therewith the peak position (quartz epsilon = 89,000 +/- 15,000 1 mol(H2O)(-1) cm(-2)), but it varies as a function of structure (coesite epsilon = 214,000 +/- 14,000 1 mol(H2O)(-1) cm(-2); stishovite epsilon = 485,000 +/- 109,000 1 mol(H2O)(-1) cm(-2)). Evaluation of data from this study confirms that not using mineral-specific IR calibrations for the OH quantification in nominally anhydrous minerals leads to inaccurate estimations of OH concentrations, which constitute the basis for modeling the Earth's deep water cycle.

In the course of a thorough study of the influences of the second coordination sphere on the crystal field parameters of the 3 d N -ions and the character of 3 d N –O bonds in oxygen based minerals, 19 natural Cr 3+ -bearing (Mg,Ca)-garnets from upper mantle rocks were analysed and studied by electronic absorption spectroscopy, EAS. The garnets had compositions with populations of the [8] X -sites by 0.881 ± 0.053 (Ca + Mg) and changing Ca-fractions in the range 0.020 ≤ w Ca[8] ≤ 0.745, while the [6] Y -site fraction was constant with x Cr 3+ [6] = 0.335 ± 0.023. The garnets had colours from deeply violet-red for low Ca-contents (up to x Ca = 0.28), grey with 0.28 ≤ x Ca ≤ 0.4 and green with 0.4 ≤ x Ca . The crystal field parameter of octahedral Cr 3+ 10Dq decreases strongly on increasing Ca-fraction from 17,850 cm −1 at x Ca[8] = 0.020 to 16,580 cm −1 at x Ca[8] = 0.745. The data could be fit with two model which do statistically not differ: (1) two linear functions with a discontinuity close to x Ca[8] ≈ 0.3, range 0.0 ≤ x_Ca[8]≤ 0.3 10Dq = ( - 2638.3x_Ca[8] ) + 17846.1 (r = 0.993) range 0.3 ≤ x_Ca[8]≤ 0.75 10Dq = ( - 1417.8x_Ca[8] ) + 17616.5 (r = 0.997) , (2) one continuous second order function, range 0.0 ≤ x_Ca[8]≤ 0.75 10Dq = 1242.1x^2_Ca[8] - 2576.5x_Ca[8] + 17,836 (r = 0.996) The behaviour of the crystal field parameter 10Dq and band widths on changing Ca-contents favour the first model, which is interpreted tentatively by different influences of Ca in the structure above and below x Ca[8] ≈ 0.3. The covalency of the Cr–O bond as reflected in the behaviour of the nephelauxetic ratio β = (B_crystal/B_free ion)_Cr^3+ , decreases on increasing Ca-contents.

A series of natural omphacites from a wide range of P, T occurrences were investigated by electron microprobe (EMP), infrared (IR)-, Mössbauer (MS)- and optical spectroscopy in the UV/VIS spectral range (UV/VIS), secondary ion mass spectrometry (SIMS) and single crystal structure refinement by X-ray diffraction (XRD) to study the influence of hydrogen loss on valence state and site occupancies of iron. In accordance with literature data we found Fe2+ at M1 as well as at M2, and in a first approach assigned Fe3+ to M1, as indicated by MS and XRD results. Hydrogen content of three of our omphacite samples were measured by SIMS. In combination with IR spectroscopy we determined an absorption coefficient: ε i,tot = 65,000 ± 3,000 lmolH2O −1 cm−2. Using this new ε i,tot value, we obtained water concentrations ranging from 60 to 700 ppm H2O (by weight). Hydrogen loss was simulated by stepwise heating the most water rich samples in air up to 800°C. After heat treatment the samples were analyzed again by IR, MS, UV/VIS, and XRD. Depending on the type of the OH defect, the grade of dehydration with increasing temperature is significantly different. In samples relatively poor in Fe3+ (<0.1 Fe3+ pfu), hydrogen associated with vacancies at M2 (OH bands around 3,450 cm−1) starts to leave the structure at about 550°C and is completely gone at 780°C. Hydrogen associated with Al3+ at the tetrahedral site (OH bands around 3,525 cm−1, Koch-Müller et al., Am Mineral, 89:921–931, 2004) remains completely unaffected by heat treatment up to 700°C. But all hydrogen vanished at about 775°C. However, this is different for a more Fe3+-rich sample (0.2 Fe3+ pfu). Its IR spectrum is characterized by a very intense OH band at 3,515 cm−1 plus shoulder at 3,450 cm−1. We assign this intense high-energy band to vibrations of an OH dipole associated with Fe3+ at M1 and a vacancy either at M1 or M2. OH release during heating is positively correlated with decrease in Fe2+ and combined with increase in Fe3+. That dehydration is correlated with oxidation of Fe2+ is indirectly confirmed by annealing of one sample in a gas mixing furnace at 700°C under reducing conditions keeping almost constant OH− content and giving no indication of Fe2+-oxidation. Obtained data indicate that in samples with a relatively high concentration of Fe2+ at M2 and low-water concentrations, i.e., at a ratio of Fe2+ M2/H > 10 dehydration occurs by iron oxidation of Fe2+ exclusively at the M2 site following the reaction: \( {\left[ {{\text{Fe}}^{{{\text{2 + [ M2]}}}}{\text{OH}}^{ - } } \right]} = {\left[ {{\text{Fe}}^{{{\text{3 + [ M2]}}}} {\text{O}}^{{{\text{2}} - }} } \right]} + {\text{1/2}}\;{\text{H}}_{{\text{2}}} \uparrow . \) In samples having relatively low concentration of Fe2+ at M2 but high-water concentrations, i.e., ratio of Fe2+ M2/H < 5.0 dehydration occurs through oxidation of Fe2+ at M1.

Inclusions in alluvial diamond from Juina (Mato Grosso, Brazil) have been investigated by TEM methods (electron diffraction, HRTEM, AEM, HAADF, EELS) and Raman spectroscopy. The inclusion paragenesis of Juina diamonds is dominated by ultrahigh-pressure ("superdeep") phases. One of these diamonds, sample # 1. 1/4, contains several micrometer-sized (approximately 200 mu m by 50-70 mu m) inclusions, which have been studied. TEM foils prepared applying Focused Ion Beam (FIB) technique revealed that these inclusions consist of a porous, nanocrystalline groundmass, which is composed of nanometre-sized crystals of a hydrous aluminium silicate phase with Al: Si approximately 1: 1 and chemical composition of phase "Egg" (AlSiO3(OH)), a minor volume fraction of nanocrystalline stishovite and pore space, which was originally filled with a fluid or gas. The nanocrystalline hydrous aluminium silicate phase is idiomorphic, randomly oriented (approximately 20-30 nm in size) predominantly with tetragonal crystal structure (a(0)=0.743 nm, c(0)=0.706 nm). The monoclinic structure of synthetic phase "Egg" determined at ambient conditions [M.W. Schmidt, L.W. Finger, R.J. Ross, R.E. Dinnebier, Synthesis, crystal structure, and phase relations of AlSiO3OH, a high-pressure hydrous phase, American Mineralogist 83 (1998) 881 - 888] is only occasionally observed. The fluid filling in the porosity has been released into the vacuum of the FIB during TEM specimen preparation. Quench products of the fluid containing minor concentrations of F- P- S- Cl- K-Ca and Ba were detected at the walls of the pores. In addition phase "Egg" is identified by mu-Raman spectroscopy within a second sample (RS 43a) from the same location. The presence of Phase "Egg" in the inclusions in diamond may suggest that crustal material has been subducted to a depth of the lower Transition Zone. Although, metastable growth of nanocrystalline high-pressure phases or extension of their respective stability fields to lower pressure can not ruled out completely. (c) 2007 Elsevier B.V. All rights reserved.

The incorporation of hydrogen in mantle olivine xenocrysts from the Udachnaya kimberlite pipe was investigated by Fourier-transform infrared spectroscopy and secondary ion mass spectrometry (SIMS). IR spectra were collected in the OH stretching region on oriented single crystals using a conventional IR source at ambient conditions and in situ at temperatures down to −180°C as well as with IR synchrotron radiation. The IR spectra of the samples are complex containing more than 20 strongly polarized OH bands in the range 3,730–3,330 cm−1. Bands at high energies (3,730–3,670 cm−1) were assigned to inclusions of serpentine, talc and the 10 Å phase. All other bands are believed to be intrinsic to olivine. The corresponding point defects are (a) associated with vacant Si sites (3,607 cm−1 E || a, 3,597 E || a, 3,571 cm−1 E || c, 3,567 E || c, and 3,556 E || b), and (b) with vacant M1 sites (most of the bands polarized parallel to a). From the pleochroic behavior and position of the OH bands associated with the vacant M1 sites, we propose two types of hydrogen—one bonded to O1 and another to O2, so that both OH vectors are strongly aligned parallel to a. The O2–H groups may be responsible for the OH bands at higher wavenumbers than those for the O1–H groups. The multiplicity of the corresponding OH bands in the spectra can be explained by different chemical environments and by slightly different distortions of the M1 sites in these high-pressure olivines. Four samples were investigated by SIMS. The calculated integral molar absorption coefficient using the IR and SIMS results of 37,500±5,000 L mol H2O cm−2 is within the uncertainties slightly higher than the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003) (28,450±1,830 L mol H2O cm−2). The reason for the difference is the different distributions of the absorption intensity of the spectra of both studies (mean wavenumber 3,548 vs. 3,570 cm−1). Olivine samples with a mean wavenumber of about 3,548 cm−1 should be quantified with the absorption coefficient as determined in this study; those containing more bands at higher wavenumber (mean wavenumber 3,570 cm−1) should be quantified using the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003).

Olivine grains from an ilmenite–garnet–peridotite nodule from the kimberlite pipe Udachnaya–Wostotschnaya, Siberia have been investigated by TEM methods (electron diffraction, HREM, AEM, EELS). The nodule is a high-temperature garnet peridotite, which equilibrated at about 1200–1300 °C and 200 km depth. TEM investigation of several olivine grains revealed nanometre-sized inclusions of (Mg,Fe,Cr)TiO3 perovskite together with ilmenite. Both types of inclusions exhibit a typical grain size of about 50 nm. The crystal structure of the perovskite inclusions is monoclinic with a0=1.095 nm, b0=0.5169 nm, c0=0.743 nm and the monoclinic angle β=95°. The orientation relationship between perovskite and olivine is (101)ol//(300)per and [010]ol//[01¯0]per. This observation combined with the experimentally determined ilmenite/perovskite phase boundary [A. Metha, K. Leinenweber, A. Navrotsky, M. Akaogi, Calorimetric study of high-pressure polymorphism in FeTiO3: stability of the perovskite phase, Phys. Chem. Minerals, 21 (1994) 207–212] [8] allows the use of perovskite in olivine as a geobarometer. The presence of perovskite in olivine suggests that the peridotite originated at pressures of 8–10 GPa, significantly higher than the pressure of last silicate equilibration (4.5–6.5 GPa).