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The Ti-in-muscovite geothermometer was empirically calibrated as ln[T( o C)]=7.258+0.289ln(Ti)+0.158[Mg/(Fe+Mg)]+0.031ln[P(kbar)] using ilmenite- and Al 2 SiO 5 -bearing assemblages in metapelites under P–T conditions of 450–800°C and 0.1–1.4GPa. The calibration was conducted for muscovites containing Ti=0.01–0.07, Fe=0.03–0.16, Mg=0.01–0.32 and Mg/(Fe+Mg)=0.05–0.73, respectively,...
Zircons from two Myanmar jadeitite samples were separated for texture, mineral inclusion, U–Pb dating and trace element composition analyses. Three types of zircons, with respect to U–Pb isotope system, were recognized. Type I zircons are inherited ones, yielding an igneous protolith age of 160±1Ma; Type II zircons are metasomatic/hydrothermal ones, giving a (minimum) jadeitite formation age of 77±3Ma;...
Equilibrium P–T conditions of garnet-facies or garnet-spinel transition facies mantle xenoliths are suggested to be best determined through a combination of the Taylor (1998) two-pyroxene thermometer either with the Taylor (1998) garnet-orthopyroxene barometer for TiO 2 -rich orthopyroxenes (Al/Ti<12.0), or with the Nickel and Green (1985) garnet-orthopyroxene barometer for TiO 2 ...
The various existing garnet–orthopyroxene geobarometers calibrated based on the Al 2 O 3 or Cr 2 O 3 components in orthopyroxene buffered by coexisting garnet for mantle xenoliths, abbreviated as Al 2 O 3 -barometer and Cr 2 O 3 -barometer, respectively, have been extensively studied, to test their precision by applying them to phase...
In this contribution we have empirically calibrated the garnet–biotite–muscovite–aluminosilicate–quartz (GBMAQ) barometer using low- to medium–high-pressure, mid-grade metapelites. Application of the barometer suggests that the GBMAQ and GASP barometers show quite similar pressure estimates. Furthermore, metapelites within thermal contact aureole or very limited geographic area show no meaningful...
At present there are many calibrations of both the garnet–biotite (GB) thermometer and the garnet–aluminum silicate–plagioclase–quartz (GASP) barometer that may confuse geologists in choosing a reliable thermometer and/or barometer. To test the accuracy of the GB thermometers we have applied the various GB thermometers to reproduce the experimental data and data from natural metapelitic rocks of various...
Placer sapphire and ruby are common in the western zone and the central/eastern zone, respectively, of the Chanthaburi-Trat (C-T) alkali basaltic gemfield in southeastern Thailand. Sapphires have O-isotope composition in the range from +5.1‰ to +6.2‰, while rubies, from +1.3‰ to +4.2‰. These data clearly show that the C-T placer sapphires and rubies should have a different primary genesis. Olivine...
Based on the net transfer reactions among garnet, muscovite, plagioclase, and quartz (for both Mg and Fe end-member models), the garnet-muscovite-plagioclase-quartz (GMPQ) geobarometry was empirically calibrated under the physical conditions of P=1.0-11.4 kbar and T=505-745 o C for 128 natural metapelitic rock samples collected from the literature. The input temperatures and pressures were...
Two empirical garnet-muscovite geothermometers, assuming no ferric iron (Model A) and 50% ferric iron (Model B) in muscovite, respectively, were calibrated under the physical conditions of P=3.0-14.0 kbar and T=530-700 o C. The input temperatures and pressures were determined by simultaneously applying the garnet-biotite thermometer [Am. Mineral. 85 (2000) 881.] and the GASP geobarometer [Am...
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