Tectonic juxtaposition of crust and continental growth during orogenesis: Example from the Rengali Province, eastern India

Abstract

a b s t r a c tThe southern boundary of the Singhbhum Craton witnessed multiple orogenies that juxtaposed thin slice of granulite suite of the Rengali Province against the low-grade granite-greenstone belt of the craton along the EeW trending Sukinda Thrust. The strong southerly dipping mylonitic foliation within the granulites along with the prominent down-dip mineral lineation, suggest a northerly-verging thrusting. Mylonitized charnockite at the contact zone contains enclaves of mafic and ultramafic granulite, whereas granitoid gneiss contains enclaves of pelitic granulite. Mafic granulite enclaves preserve an early (S 1M ) foliation that formed during D 1M deformation. This rock, along with the host charnockite, were intensely deformed by the D 2M thrusting event and resulting S 2M foliation development in both rock suites. Geothermobarometric and pseudosection analyses show that the garnet-clinopyroxene-plagioclaseorthopyroxene-ilmenite-quartz assemblage in mafic granulite was stabilized at high-pressure and temperature conditions (10À12 kbar, 860 C) and was overprinted by a fine-grained assemblage of clinopyroxene-plagioclase AE hornblende that developed during decompression (down to 5.5e7.5 kbar). Matrix hornblende shows incipient breakdown to garnet-clinopyroxene-quartz intergrowth due to a granulite facies reworking. A contrasting P-T history is preserved in the pelitic granulite. The peak assemblage garnet-orthopyroxene-cordierite-quartz-rutile was stabilized at w6.0 kbar, 730 C which resulted from heating of the mid crust magma during the D 2M thrusting. The contrasting P-T histories could result from the tectonic juxtaposition of lower-and mid-crustal section during the D 2M event. Evidences of an early orogenic imprint within the mafic granulite imply involvement of deep continental crust during southward growth of the Singhbhum Craton.Ó 2014, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/3.0/).

Petrological and geochemical evolution of the Central Gneissic Belt, Rengali Province, eastern India: Implications for the Neoarchean growth and orogenesis

“…The linear belt of high-grade rocks containing charnockite gneiss, mafic granulite, granite gneiss and pelitic granulites constitute the Central Gneissic Belt . This belt extends up to Bhuban in eastern part where the granulites of the Central Gneissic Belt are juxtaposed against the granulites of the Eastern Ghats Province (Bose et al, 2015). Mafic granulites from the eastern part of the Central Gneissic Belt indicate a high-pressure (11-12 kbar) metamorphism followed by cooling and decompression to mid-crustal level (Bose et al, 2015).…”

“…This belt extends up to Bhuban in eastern part where the granulites of the Central Gneissic Belt are juxtaposed against the granulites of the Eastern Ghats Province (Bose et al, 2015). Mafic granulites from the eastern part of the Central Gneissic Belt indicate a high-pressure (11-12 kbar) metamorphism followed by cooling and decompression to mid-crustal level (Bose et al, 2015). Pelitic granulite, on the other hand, records much lower pressure (6-8 kbar) granulite metamorphism (Mahapatro et al, 2012;Bose et al, 2015).…”

“…Mafic granulites from the eastern part of the Central Gneissic Belt indicate a high-pressure (11-12 kbar) metamorphism followed by cooling and decompression to mid-crustal level (Bose et al, 2015). Pelitic granulite, on the other hand, records much lower pressure (6-8 kbar) granulite metamorphism (Mahapatro et al, 2012;Bose et al, 2015).…”

“…2800 Ma orogenesis (Bose et al, 2015). Available geochronological data suggest an event of high-grade metamorphism and granitoid magmatism at ca.…”

“…2860-2780 Ma. Bose et al (2015) argued that this tectonothermal pulse resulted in partial melting, granulite metamorphism and magma emplacement in a subduction-accretioncollision cycle. All the rocks of the Central Gneissic Belt witnessed a second phase of highgrade metamorphism at ca.…”