Ultrahigh-temperature mafic granulites from Panrimalai,south India: Constraints from phase equilibria and thermobarometry |
| |
| Institution: | 1. Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France;2. Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France;3. Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France;4. Centre Terrae Genesis, F-88120 Le Syndicat, France;1. Departent of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302, India;2. Univ Rennes, CNRS, Geosciences Rennes, UMR 6118, 35000 Rennes, France;3. School of Earth, Ocean and Atmospheric Sciences, Goa University, Taleigao Plateau, Goa 403206, India;1. Department of Marine Geology and Geophysics, Cochin University of Science and Technology, Lakeside Campus, Kochi 16, India;2. Center for Tectonics, Resources and Exploration, Department of Earth Sciences, University of Adelaide, SA 5005, Australia;3. School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China;4. Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan;5. Department of Geology, University of Johannesburg, Auckland Park 2006, South Africa;6. CSIR — National Geophysical Research Institute, Hyderabad 500007, India |
| |
| Abstract: | The Panrimalai area constitutes part of the granulite-facies rocks of the Madurai block in the Southern Granulite Terrain (SGT), India. Garnet-bearing mafic granulites in Panrimalai occur as small enclaves within charnockite. The common stable assemblage during peak metamorphism contains hornblende, garnet, orthopyroxene, clinopyroxene, quartz and plagioclase. The resorption of garnet in various reaction textures and the development of spectacular orthopyroxene–plagioclase and hornblende–plagioclase symplectites characterize the subsequent stages of metamorphism. Application of multi-equilibrium calculation procedures for mineral core compositions of the early assemblage yields near peak conditions at ≥ 900 °C at 9 kbar. These estimates are the highest yet reported in mafic granulites from the Madurai block. The post-peak P–T path is constructed for the mafic granulites based on observed microstructural relations and thermobarometric results is characterized by a steep clockwise decompressional P–T segment from ≥ 9 to < 4.5 kbar. Constraints from model Nd ages provide evidence for Paleoproterozoic magmatism restricted to the Madurai block in the Southern Granulite Terrain. The early part of the crustal evolution of the Panrimalai granulites could be coeval with the Paleoproterozoic event. Subsequent development of symplectitic assemblages via near-isothermal decompression can be ascribed to a distinctly later tectonic event. Available U–Pb and Sm–Nd mineral dates suggest a widespread Pan-African tectonothermal event in the SGT. Given the general recognition of ultrahigh-temperature (UHT) and isothermal decompression (ITD) in Pan-African age metamorphism in the East-African–Antarctic Orogen (EAAO) , the Panrimalai UHT history is considered to be part of this record. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
