Petrology and fluid inclusions of garnet-clinopyroxene rocks from Paramati in the Palghat-Cauvery Shear Zone System, southern India

• NISHIMIYA Yuki

  Graduate School of Life and Environmental Sciences (Earth Evolution Sciences), University of Tsukuba

• TSUNOGAE Toshiaki

  Graduate School of Life and Environmental Sciences (Earth Evolution Sciences), University of Tsukuba Department of Geology, University of Johannesburg

• SANTOSH M.

  Department of Natural Environmental Science, Faculty of Science, Kochi University

抄録

We report petrological and fluid inclusion data on garnet-clinopyroxene rocks from Paramati in the Palghat-Cauvery Shear Zone System, southern India. The rocks are composed of garnet, clinopyroxene, and plagioclase with or without orthopyroxene and retrograde pargasite. The peak P-T conditions of 9-12 kbar and 830-880 °C were obtained from early garnet-clinopyroxene-plagioclase-quartz assemblage. Available petrological data from this region suggest that the high-pressure event was followed by heating to the peak ultrahigh-temperature condition and decompression as supported by the occurrence of orthopyroxene + plagioclase symplectite between garnet + clinopyroxene and plagioclase lamella in clinopyroxene. High Ca-Eskola molecule in the integrated clinopyroxene (∼ 8.6%) is also comparable with its high-pressure origin. Primary and secondary fluid inclusions in garnet are dominantly CO₂-rich. They were homogenized into the liquid phase in the temperature range of −11.1 to +14.2 °C, corresponding to low-CO₂ densities of 0.82 to 0.99 g/cm³. The fluid densities, when computed into isochores, indicate lower pressures (∼ 6-7 kbar at 900 °C) than the P-T conditions estimated by geothermobarometry. The low-density values and the primary nature of the inclusions trapped in garnet, as well as wide variation in homogenization temperatures, indicate density modification of prograde metamorphic fluid during exhumation. The results of this study support prograde high-pressure metamorphism and subsequent decompression along a clockwise P-T path for the evolution of the rocks in this Gondwana suture zone probably related to subduction of crustal materials to the mantle depth (>40 km) and following continent-continent collision during the amalgamation of the Gondwana Supercontinent.

収録刊行物

• Journal of Mineralogical and Petrological Sciences

  Journal of Mineralogical and Petrological Sciences 103 (5), 354-360, 2008

  一般社団法人　日本鉱物科学会

キーワード

• Garnet-clinopyroxene rock
• Fluid inclusions
• High-pressure and ultrahigh-temperature metamorphism
• Palghat-Cauvery Shear Zone System
• Southern India
• Gondwana supercontinent

詳細情報

• CRID: 1390001206546114048
• NII論文ID: 10022079523
• NII書誌ID: AA11460926
• DOI: 10.2465/jmps.080617
• ISSN: 13493825
• ISSN: 13456296
• 本文言語コード: en
• データソース種別:
  • JaLC
  • Crossref
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可