TY - JOUR
T1 - Ultrahigh-temperature metamorphism followed by two-stage decompression of garnet-orthopyroxene-sillimanite granulites from Ganguvarpatti, Madurai block, southern India
AU - Sajeev, K.
AU - Osanai, Y.
AU - Santosh, M.
N1 - Funding Information:
Acknowledgements We are grateful to Simon Harley and G.T.R Droop for their critical and constructive comments, and patient suggestions by the editor Ian Parsons which improved this manuscript. The first author is thankful to H. Mouri and M. Satish-Kumar for personal discussions and their comments on this work. The fieldwork was partly supported from the project led by M. Yoshida. This work was supported by the Grand-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan, to Y. Osanai, No. 14340150. This work is a contribution to IGCP 368 and 440.
PY - 2004/9
Y1 - 2004/9
N2 - The Mg-Al granulites from Ganguvarpatti consist of orthopyroxene-sillimanite-garnet ± quartz as peak assemblage, with a few porphyroblasts of cordierite and sapphirine. These assemblages were strongly overprinted by late symplectites and coronas. Orthopyroxene inclusions in garnet and porphyroblast cores have the highest XMg (0.80) and A12O3 content (10.7 wt%). The estimated near-peak metamorphic conditions (1,000 ± 50°C and 11 kbar) using garnet-orthopyroxene geothermobarometry are consistent with those determined using a petrogenetic grid. The proposed multi-stage evolution process implies an initial decompression, deduced from multi-phase symplectites, followed by cooling during biotite formation. Further late decompression is explained from the orthopyroxene rims on biotite. This proposed P-T path thus suggests a unique and complex evolution history for the UHT granulites of southern India. Present results are comparable with similar adjacent terranes in the Gondwana supercontinent, but the lack of structural and geochronological data makes a link with any major metamorphic event uncertain.
AB - The Mg-Al granulites from Ganguvarpatti consist of orthopyroxene-sillimanite-garnet ± quartz as peak assemblage, with a few porphyroblasts of cordierite and sapphirine. These assemblages were strongly overprinted by late symplectites and coronas. Orthopyroxene inclusions in garnet and porphyroblast cores have the highest XMg (0.80) and A12O3 content (10.7 wt%). The estimated near-peak metamorphic conditions (1,000 ± 50°C and 11 kbar) using garnet-orthopyroxene geothermobarometry are consistent with those determined using a petrogenetic grid. The proposed multi-stage evolution process implies an initial decompression, deduced from multi-phase symplectites, followed by cooling during biotite formation. Further late decompression is explained from the orthopyroxene rims on biotite. This proposed P-T path thus suggests a unique and complex evolution history for the UHT granulites of southern India. Present results are comparable with similar adjacent terranes in the Gondwana supercontinent, but the lack of structural and geochronological data makes a link with any major metamorphic event uncertain.
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U2 - 10.1007/s00410-004-0592-0
DO - 10.1007/s00410-004-0592-0
M3 - Article
AN - SCOPUS:4544265313
SN - 0010-7999
VL - 148
SP - 29
EP - 46
JO - Contributions to Mineralogy and Petrology
JF - Contributions to Mineralogy and Petrology
IS - 1
ER -