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Hot orogens and supercontinent amalgamation: A Gondwanan example from southern India |
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| Institution: | 1. Department of Applied Geology, Curtin University, Perth WA 6845, Australia;2. School of Geosciences, King''s College, University of Aberdeen, AB24 3UE United Kingdom;3. Department of Earth Sciences, The University of Adelaide SA 5005, Australia;4. School of Earth Science & Resources, Chinese University of Geosciences, Beijing, China;1. Departamento de Mineralogia e Petrologia, Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, CEP 05508-080, São Paulo, SP, Brazil;2. Department of Geology, The University of Kansas, 2335 Irving Hill Road, Nichols Hall, Lawrence, KS, 66045-7559, USA;3. Department of Geosciences, University of Massachusetts, 611 North Pleasant Street, Amherst, MA, 01003-9297, USA;1. Geological Faculty, Moscow State University, Leninskie Gory, Moscow 119234, Russia;2. Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka 142432, Russia;3. Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Johannesburg, South Africa;4. Department of Earth Sciences, Swiss Federal Institute of Technology, CH-8092 Zürich, Switzerland |
| Abstract: | The Southern Granulite Terrane in southern India preserves evidence for regional-scale high to ultrahigh temperature metamorphism related to the amalgamation of the supercontinent Gondwana. Here we present accessory mineral (zircon and monazite) geochronological and geochemical datasets linked to the petrological evolution of the rocks as determined by phase equilibria modelling. The results constrain the duration of high to ultrahigh temperature (> 900 °C) metamorphism in the Madurai Block to be c. 40 Ma with peak conditions achieved c. 60 Ma after the formation of an orogenic plateau related to the collision of the microcontinent Azania with East Africa at c. 610 Ma. A 1D numerical model demonstrates that the attainment of temperatures > 900 °C requires that the crust be moderately enriched in heat producing elements and that the duration of the orogenic event is sufficiently long to allow conductive heating through radioactive decay. Both of these conditions are met by the available data for the Madurai Block. Our results constrain the length of time it takes for the crust to evolve from collision to peak P–T (i.e. the prograde heating phase) then back to the solidus during retrogression. This evolution illustrates that not all metamorphic ages date sutures. |
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