Tectonics of the Neoproterozoic Southern Granulite Terrain, South India

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• 作者：Cenki ; B脙脙n脙脙dicte ; Kriegsman ; Leo M.
• 关键词：Gondwana ; South India ; Tectonics ; Granulites ; Pan-African age
• 刊名：Precambrian Research
• 出版年：2005
• 期刊代码：75_03019268
• 类别：ear
• 出版时间：July 6, 2005
• 卷：138
• 期：1-2
• 页码：37-56
• 文件大小：1.54 M

摘要

Geological correlations between South India and adjacent Gondwana fragments are hampered by the lack of a coherent structural framework for India's Southern Granulite Terrain (SGT). This paper is an attempt at delineating its large-scale geometry and Neoproterozoic kinematics and tectonics. The basic regional pattern is that of a high-grade gneissic layering produced during several deformation stages (grouped as D₁), which became refolded during two regionally separated phases of upright folding (D_2a: NNW trending; D_2b: NE trending) and reworked in E- to ESE-trending zones of increased strain (D₃). Of these, the Palghat Cauvery Shear Zone (PCSZ), which marks the boundary between Archaean terrains in the north and Proterozoic belts in the south, may represent a major crustal shear zone, whereas the Achankovil Zone (AZ) is better considered as a high-strain zone characterized by flattening with a reverse component. D₁ structures developed close to the peak of Pan-African high-grade metamorphism. D_2a and D_2b occurred on the retrograde path, partly at supersolidus and partly at subsolidus conditions. D₃ high-strain zones show subsolidus textures. In view of the general clockwise nature with a clear decompressional component of all published P–T paths, we propose that D₂–D₃ occurred during partial exhumation of the terrain. Correlations with Madagascar are weakened as the AZ is no longer considered a major crustal shear zone, whereas correlations with Sri Lanka are strengthened by the presence of a similar syntactical bend possibly produced by an indentor.