Sodicgedrite in ultrahigh-temperature Mg-Al-rich rocks from the Palghat-Cauvery Shear Zone system, southern India

• 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

• SHIMPO Makoto

  Master's Program in Education, University of Tsukuba

Abstract

We report high-Na gedrite (sodicgedrite) with up to 3.1 wt% Na₂O (∼ 0.81 Na^A pfu) in ultrahigh-temperature (UHT) Mg-Al-rich rocks from the northern margin of the Pan-African Madurai Block along the Palghat-Cauvery Shear Zone system, southern India. An amount of Na^A of the gedrite increases with increasing Al^IV. The sum of Na^A and Al^IV also increases linearly with decreasing Si suggesting the substitution of Na^AAl^IV ↔ Si. The negative correlation between Fe + Mg + Si and Al is probably due to the tschermak substitution ((Fe,Mg)^VISi^IV ↔ Al^VIAl^IV). The relatively coarse-grained nature and porphyroblastic occurrence of the sodicgedrite suggest that the mineral recrystallized at the peak UHT metamorphism. In contrast, retrograde gedrite with cordierite is less sodic with 1.1-1.6 wt% Na₂O (Na^A = 0.24-0.35 pfu). Our data suggest that high-Na content in gedrite is a possible indicator of UHT metamorphism.

Journal

• Journal of Mineralogical and Petrological Sciences

  Journal of Mineralogical and Petrological Sciences 102 (1), 39-43, 2007

  Japan Association of Mineralogical Sciences

Keywords

• Sodicgedrite
• Ultrahigh-temperature metamorphism
• Palghat-Cauvery Shear Zone system
• Madu rai Block
• Pan-African
• Gondwana
• Southern India

Details

• CRID: 1390282681521566720
• NII Article ID: 10018411510
• NII Book ID: AA11460926
• DOI: 10.2465/jmps.060824
• ISSN: 13493825
• ISSN: 13456296
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed