Hydrous components of grossular-andradite garnets from Thailand: thermal stability and exchange kinetics

Phichaikamjornwut, Bongkot; Skogby, Henrik; Ounchanum, Prayote; Limtrakun, Phisit; Boonsoong, Apichet

doi:10.1127/0935-1221/2011/0023-2146

Cited by 9 publications

(26 citation statements)

References 25 publications

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“…As shown in Figure 2, the most prominent OH absorption bands are located at 3612, 3583, 3564 cm -1 and a minor band is found at 3634 cm -1 . These OH absorptions are typical of andradite from a skarn (Amthauer and Rossman 1998), and resemble the Ti-bearing andradite described by Armbruster et al (1998) and the KPK 54-9 andradite An 99 from Phu Kha Hill, Thailand, used by Phichaikamjornwut et al (2012) to study hydrogen dehydration and rehydration. Using Gaussian and Lorentzian (for bands at 3641 and 3526 cm -1 ) shapes, spectral peak-deconvolution using Peakfit software (SPSS Inc.) leads to 12 different peaks located at 3641,3634,3628,3621,3612,3605,3596,3583,3575,3564,3547,3526, and a small broad band of water at 3406 cm -1 , probably due to the presence of some fluid inclusions (Fig.…”

Section: Experimental Data From H-d and D-h Exchangementioning

confidence: 95%

“…It has been shown that it is difficult to model the evolution of H concentration of garnets with time by a simple diffusion process (Kurka 2005;Phichaikamjornwut et al 2012). This is particularly true for andradite garnets where it was frequently observed that 10 to 20% of the original H content remained in the crystal after annealing (Kurka 2005;Phichaikamjornwut et al 2012). Several explanations were proposed for this behavior but no definitive solution was found.…”

Section: Introductionmentioning

confidence: 94%

“…These studies have shown that the activation energies of the extraction laws are much higher than in most ferromagnesian silicates; they range between 200 and 350 kJ/mol and the diffusion coefficients cover two orders of magnitude in the temperature range of 700-1050 °C. It has been shown that it is difficult to model the evolution of H concentration of garnets with time by a simple diffusion process (Kurka 2005;Phichaikamjornwut et al 2012). This is particularly true for andradite garnets where it was frequently observed that 10 to 20% of the original H content remained in the crystal after annealing (Kurka 2005;Phichaikamjornwut et al 2012).…”

Section: Introductionmentioning

confidence: 95%

“…Few studies on the diffusion of hydrogen in garnets have been published (pyrope: Wang et al 1996;Ingrin 2004a, 2004b; grossular: Kurka et al 2005;andradite: Kurka 2005;Ingrin and Blanchard 2006;Phichaikamjornwut et al 2012). These studies have shown that the activation energies of the extraction laws are much higher than in most ferromagnesian silicates; they range between 200 and 350 kJ/mol and the diffusion coefficients cover two orders of magnitude in the temperature range of 700-1050 °C.…”

Section: Introductionmentioning

confidence: 96%

“…Furthermore, the mechanisms involved in H extraction in garnets remain largely unknown. Although, the redox-reaction Fe 2+ + OH -= Fe 3+ + O 2-+ 1 ⁄2H 2 seems to be a possible candidate for pyrope and grossular (Blanchard and Ingrin 2004b;Forneris and Skogby 2004;Kurka 2005;Kurka et al 2005), this process is not available for H extraction in andradites, which dominantly contain Fe 3+ (Phichaikamjornwut et al 2012).…”

Section: Introductionmentioning

confidence: 96%

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Kinetics of deuteration in andradite and garnet

Zhang

Ingrin

Depecker

et al. 2015

American Mineralogist

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The hydrogen mobility in andradite single crystals from an iron-skarn deposit was investigated through H-D and D-H exchange experiments. Thin slices were annealed in a horizontal furnace flushed with a gas mixture of Ar/D 2(10%) and Ar/H 2(10%) at ambient pressure between 400 and 700 °C. FTIR analyses were performed before and after each annealing run. Between 15 and 35% of the original OH content remained in the crystal structure at the end of the deuteration experiments. This contrasts with the results of similar experiments performed in other NAMs, where all hydrogen atoms are replaced by deuterium in the structure. However, because a steady state was reached at the end of the experiments, the diffusion law for the exchange process was determined as: D H-D = D 0 exp[-(96 ± 11) kJ/mol/RT], with logD 0 = -5.9 ± 0.7 (in m 2 /s). The activation energy is similar to that for hydrogen diffusion in grossular, but H diffusivity is more than two orders of magnitude faster. Our results demonstrate that, because major element composition has a major effect on H-D diffusion laws, it must be considered in any discussion of δD signatures in garnets. In andradite-rich garnets, hydrogen isotope data can only be used to record short, low-grade metamorphic or metasomatic events, at temperatures lower than 400 °C.

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Section: Experimental Data From H-d and D-h Exchangementioning

confidence: 95%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

See 3 more Smart Citations

Kinetics of deuteration in andradite and garnet

Zhang

Ingrin

Depecker

et al. 2015

American Mineralogist

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Experimental constraints on hydrogen diffusion in garnet

Reynes

Jollands

Hermann

et al. 2018

Contrib Mineral Petrol

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The incorporation mechanisms and diffusional loss of hydrogen in garnet have been experimentally investigated. A suite of gem-quality hydrous spessartine-and grossular-rich garnets were analysed by Fourier transform infrared spectroscopy (FTIR) and by ion microprobe (SHRIMP-SI) to determine the calibration coefficients for quantification of FTIR data. The excellent agreement between measured absorption and OH/O indicates that the same molar extinction coefficient can be used for spessartine and grossular. The coefficient of 14400 l mol − 1 cm − 2 proposed by Maldener et al. (Phys Chem Miner 30:337-344, 2003) seems the most appropriate for both minerals. A grossular with 6.4% andradite and 1.6% almandine containing 834 ppm H 2 O, and an almost pure spessartine with 282 ppm H 2 O, were selected for diffusion experiments. 1.5-mm cubes of garnets were heated between 12 h and 10 days at 1 atm under various temperature (750-1050 °C) and oxygen fugacity ( f O 2 ) conditions, (ΔQFM + 15.2 to − 3.0). Diffusion profiles were acquired from sections through the cubes using FTIR, with a deconvolution algorithm developed to assess peak-specific behaviour. Different families of peaks have been identified based on their diffusive behaviour, representing hydrogen incorporated in different H-bearing defects. A dominant, fast, strongly f O 2 -dependent oxidation-related diffusion mechanism is proposed) with a relatively low activation energy (158 ± 19 kJ mol − 1 ). This diffusion mechanism is likely restricted by availability of ferrous iron in grossular. At low oxygen fugacity, this diffusion mechanism is shut off and the diffusivity decreased by more than three orders of magnitude. A second, slower hydrogen diffusion mechanism has been observed in minor bands, where charge balance might be maintained by diffusion of cation vacancies, with much higher activation energy (≈ 200-270 kJ mol − 1 ). Spessartine shows clear differences in peak retentivity suggesting that up to four different H sites might exist. This opens exciting opportunities to use hydrogen diffusion in garnet as speedometer. However, it is essential to constrain the main diffusion mechanisms and the oxygen fugacity in the rocks investigated to obtain timescales for metamorphic or igneous processes.

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