Multiple tectonometamorphic imprints in the lower crust: first evidence of ca. 950 Ma (zircon U-Pb SHRIMP) compressional reworking of UHT aluminous granulites from the Eastern Ghats Belt, India

作者：Das Kaushik^*; Bose Sankar; Karmakar Subrata; Dunkley Daniel J; Dasgupta Somnath

来源：Geological Journal, 2011, 46(2-3): 217-239.

DOI：10.1002/gj.1246

• deep crustal reworking
• Eastern Ghats Belt
• India
• UHT aluminous granulites
• zircon U-Pb SHRIMP ages

Integrated structural, petrological and geochronological study on a suite of granulites from the central part of the Eastern Ghats Belt (EGB), India unveil polyphase tectonothermal evolution. We document (a) M(1) ultrahigh temperature (UHT) metamorphism (similar to 1000 degrees C at 6.5-8.5 kbar) on an anticlockwise P-T trajectory simultaneously with early deformations D(1)-D(2) involving partial melting, (b) cooling down to similar to 800 degrees C, 6 kbar that produced a variety of coronae/symplectites (M(1R)), (c) an unrelated compressional orogeny (D(3)) that produced deep crustal shears and mylonitic foliation (S(3m)) at low angles to D(1)-D(2) structures and was associated with slight loading, and possible partial melt extraction under granulite facies condition (M(2) similar to 7 kbar, 850 degrees C), and (d) localized retrogression (M(3)) in the presence of melt accompanying D(4) deformation. This is the first record of the prograde P-T path of the superimposed granulite facies metamorphism in the EGB. U-Pb SHRIMP data of zircon preserves an inherited grain domain of ca. 1700 Ma ((207)Pb-(206)Pb age) that traces back the history of EGB with a lineage of the Mesoproterozoic supercontinent, Columbia. The UHT metamorphosed (peak M(1) at ca. 1000 Ma) and subsequently cooled crustal segment (M(1R)) was subjected to strong tectonothermal reworking (M(2)) along a clockwise P-T path at 953 + 6 Ma (concordia age) that partially exhumed the rocks to mid-crustal levels. A later fluid-induced retrogressive event vis-a-vis melt crystallization occurred at ca. 900 Ma ((207)Pb-(206)Pb age). The post-peak evolution reveals striking similarities with those recorded in the rocks of the Rayner Complex of east Antarctica, thereby strengthening the notion of Indo-Antarctic correlation as part of Rodinia.

• 出版日期2011-6
• 单位中国极地研究中心