High-temperature metamorphic imprint on calc-silicate granulites of Rayagada, Eastern Ghats, India: Implication for the isobaric cooling path

R. K. Shaw, M. Arima

研究成果: Article査読

32 被引用数 (Scopus)

抄録

Calc-silicate granulites from Rayagada, north-central sector of Eastern Ghats granulite belt show a wide range of mineral assemblages and chemical compositions, which can be grouped as Gr. I (grossular-rich garnet-wollastonite-scapolite-calcite-clinopyroxene), Gr. II (andradite-rich garnet-scapolite-calcite-clinopyroxene), and Gr. III (scapolite-calcite-clinopyroxeneplagioclase) assemblages. Petrographic features suggest the following several reactions in the CaO-Al2O3 - SiO2-vapor system: Mei + 4Wo + Cal = 3Grs + Qtz + 2CO2, Mei + 3Wo + 2Cal = 3Grs + CO2, Mei = 3An + Cal, Wo + CO2 = Cal + Qtz, Mei + 5Wo = 3Grs + 2Qtz + CO2, An + Wo = Grs + Qtz, Mei + 5Cal + 3Qtz = 3Grs + 6CO2, and the following reactions in the CaO-FeO-MgO-Al2O3-SiO2-vapor system: Cpxss + Scp + Wo = Grtss + Qtz + CO2, 4Hd + 2Cal + O2 = 2Adr + 2Qtz + 2CO2, Cpxss + Scp = Grtss + Cal + Qtz. These reactions have been used to estimate peak T-XCO2 condition for these granulites. A maximum temperature of ∼920°C has been calculated at an estimated pressure of 9 kbar. A T-XCO2 diagram shows an isobaric cooling from ∼920°C to ∼815°C. A range of XCO2 (0.50 at 920°C to 0.25 at 815°C) has been observed for Gr. I calc-silicate granulites based on the reaction sequences including coronal garnet-forming reactions. This sequence is suggestive of internal fluid buffering rather than external fluid influx and the differences in XCO2 conditions has been thought to be due to local buffering of fluid phases. Group II and Gr. III calc-silicate granulites, on the other hand, exhibit relatively lower temperature conditions.

本文言語English
ページ(範囲)169-180
ページ数12
ジャーナルContributions to Mineralogy and Petrology
126
1-2
DOI
出版ステータスPublished - 1996 12月
外部発表はい

ASJC Scopus subject areas

  • 地球物理学
  • 地球化学および岩石学

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