Hydroxyl-rich topaz in high-pressure and ultrahigh-pressure kyanite quartzites, with retrograde woodhouseite, from the Sulu terrane, eastern China

Zhang, Ru Y.; Liou, J. G.; Shu, Jiang

doi:10.2138/am-2002-0408

Cited by 92 publications

(46 citation statements)

References 27 publications

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“…9c), two groups of K-white micas are identified. The first one is composed of Si-rich phengites (Si **: Zhang et al, 1995Zhang et al, , 2000Zhang et al, and 2002bLiu et al, 2001;. * not taken into account for average P calculation Yang, 2003Zhang et al, 2006b and PT path: Zhang et al, 2005bZhang et al, 2000Zhang et al, 2005aZhang et al, 2006a T calculated at P > 2.8 GPa ** felsic rocks mafic rocks…”

Section: Application To Natural Samples-discussionmentioning

confidence: 99%

Titanium in phengite: a geobarometer for high temperature eclogites

Auzanneau

Schmidt

Vielzeuf

et al. 2009

Contrib Mineral Petrol

181

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Phengite chemistry has been investigated in experiments on a natural SiO 2 -TiO 2 -saturated greywacke and a natural SiO 2 -TiO 2 -Al 2 SiO 5 -saturated pelite, at 1.5-8.0 GPa and 800-1,050°C. High Ti-contents (0.3-3.7 wt %), Ti-enrichment with temperature, and a strong inverse correlation of Ti-content with pressure are the important features of both experimental series. The changes in composition with pressure result from the Tschermak substitution (Si ? R 2? = Al IV ? Al VI ) coupled with the substitution:The latter exchange is best described using the end-member Ti-phengite (KMgTi[Si 3 Al]O 10 (OH) 2 , TiP). In the rutile-quartz/coesite saturated experiments, the aluminoceladonite component increases with pressure while the muscovite, paragonite and Ti-phengite components decrease. A thermodynamic model combining data obtained in this and previous experimental studies are derived to use the equilibrium MgCel ? Rt = TiP ? Cs/Qz as a thermobarometer in felsic and basic rocks. Phengite, rutile and quartz/coesite are common phases in HT-(U)HP metamorphic rocks, and are often preserved from regression by entrapment in zircon or garnet, thus providing an opportunity to determine the T-P conditions of crystallization of these rocks. Two applications on natural examples (Sulu belt and Kokchetav massif) are presented and discussed. This study demonstrates that Ti is a significant constituent of phengites that could have significant effects on phase relationships and melting rates with decreasing P or increasing T in the continental crust.

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Section: Application To Natural Samples-discussionmentioning

confidence: 99%

Titanium in phengite: a geobarometer for high temperature eclogites

Auzanneau

Schmidt

Vielzeuf

et al. 2009

Contrib Mineral Petrol

181

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“…The range of the (OH,F)-solid solution was previously thought to be limited up to X OH = 0.5 [X OH = OH/(OH + F)] due to proton-proton avoidance (Barton 1982). However, finding of OH-rich topaz with X OH = 0.55 in samples from ultrahigh-pressure rocks of the Sulu terrane, eastern China (Zhang et al 2002), as well as experimental studies at high pressure indicate that depending on the P -T -X-conditions, topaz might be stable along the complete (OH,F)-solid solution series (Wunder et al 1993(Wunder et al , 1999. The existence of topaz with X OH = 1.0 was first predicted from energy calculations (Abbott 1990) and confirmed later by high-pressure synthesis (Wunder et al 1993).…”

Section: Introductionmentioning

confidence: 95%

“…Topaz, Al 2 SiO 4 (F, OH) 2 , is a well-known hydrous mineral in aluminous and fluorine-rich rocks occurring in near-surface environments (e.g., Ribbe 1982); less often it is also found in low-temperature, high-to ultrahigh-pressure metamorphic rocks (Theye 1988;Zhang et al 2002). The range of the (OH,F)-solid solution was previously thought to be limited up to X OH = 0.5 [X OH = OH/(OH + F)] due to proton-proton avoidance (Barton 1982).…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of the OH-stretching frequencies in topaz-OH

Watenphul

Wunder

2009

Phys Chem Minerals

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Hydrogen bonding in topaz-OH, Al 2 SiO 4 (OH) 2 , was investigated by IR spectroscopic analysis of the temperature dependence of the OH-stretching frequencies. Low-temperature spectra ranging from -196 to -160 • C prove the existence of four non-equivalent H-positions in the crystal structure from the occurrence of four different OH-bands. With increasing temperature, these bands merge first, above -160 • C, into two OH-bands and then above 400 • C into one asymmetric broad band. Shifting of the OH-bands is caused by thermally induced hydrogen order-disorder. Low temperature fixes the protons in their positions; increasing temperature induces proton movement and allows switching between the different positions. Autocorrelation analysis of the IR spectra reveals two phase transitions, one at about -155 • C from P1 to Pbn2 1 characterized as static-dynamic change and the second at about 380 • C from Pbn2 1 to Pbnm caused by disordering of the protons. The increasing symmetry with temperature is due to advanced proton movement and dynamical averages over the proton distribution densities.

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“…Topaz of an X OH content of up to 0.55, which is the highest ever found in nature, has recently been described for an occurrence in ultrahigh-pressure rocks of the Sulu terrane, Eastern China (Zhang et al 2002). The OH endmember of topaz (topaz-OH), Al 2 SiO 4 (OH) 2 , was first synthesized by Wunder et al (1993) in multi-anvil experiments at high pressures above 7.0 GPa.…”

Section: Introductionmentioning

confidence: 99%

Ab-initio calculations of the proton location in topaz-OH, Al 2 SiO 4 (OH) 2

Churakov¹,

Wunder

2004

Physics and Chemistry of Minerals

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The position of hydrogen in the structure of topaz-OH was determined by means of ab-initio quantum-mechanic calculations. Static lattice energy calculations predict the existence of four non-equivalent positions of protons, which are characterized by O4-H1…O1, O4-H2…O2, O4-H3…O3 and O4-H4…O4 hydrogen bonds. The distribution of the protons between positions of local equilibrium is controlled by the proton-proton avoidance rule and the strength of the hydrogen bonds. The most favourable configuration of hydrogen atoms is achieved for adjacent protons, which form O4-H3…O3 and O4-H4…O4 hydrogen bonds, respectively. The thermal excitation of atoms at a temperature of 55 K is large enough for the hydrogen atoms occasionally to change their positions to form O4-H1…O1 and O4-H2…O2 bonds. At ambient pressures and higher temperatures the protons are in a dynamic exchange between the allowed positions of local minima. As a consequence, for nearly room-temperature conditions, the dynamic change between different structural configurations leads to the violation of all possible symmetry elements and with that to space group P1. The flipping of the protons between different sites is achieved by simple rotation of the OH-dipole and does not produce any significant distortion of the framework of topaz, whose symmetry remains that of the space group Pbnm. Therefore, no reduction of symmetry has been observed in former X-ray studies on topaz-OH. Calculated IR absorption spectra of topaz-OH were found to be in good agreement with measured spectra. According to the calculations, the two favourable configurations of protons might correspond to the measured peak splitting within the OH-stretching range. An experimentally observed low-frequency band at 3520 cm )1 was assigned to the OH-stretching of the O4-H3…O3 bond, while the band at 3600 cm )1 was attributed to OH-stretching of the O4-H4…O4 hydrogen bond. The broad peak in FAR-IR frequency range at 100-150 cm )1 is attributed to the stretching of H3…O3 and H4…O4 contacts. The rate of proton exchange at 670 K among different sites was estimated by ab-inito molecular dynamic simulations. The calculations predict that flipping of adjacent protons between O4-H3…O3 and O4-H4…O4 bonds at 670 K occur at a rate of about 1.96 THz.

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Hydroxyl-rich topaz in high-pressure and ultrahigh-pressure kyanite quartzites, with retrograde woodhouseite, from the Sulu terrane, eastern China

Cited by 92 publications

References 27 publications

Titanium in phengite: a geobarometer for high temperature eclogites

Titanium in phengite: a geobarometer for high temperature eclogites

Temperature dependence of the OH-stretching frequencies in topaz-OH

Ab-initio calculations of the proton location in topaz-OH, Al 2 SiO 4 (OH) 2

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