Neoarchaean crustal reworking in the Aravalli Craton: Petrogenesis and tectonometamorphic history of the Malola granite, Bhilwara area, northwestern India. (3rd August 2020)

• Record Type: Journal Article
• Authors: D'Souza, Joseph; Sheth, Hetu; Xu, Yigang; Wegner, Wencke; Prabhakar, N.; Sharma, Kamal Kant; Koeberl, Christian
• Is Part Of: Geological journal. Volume 55:Number 12(2020)
• Page Start: 8186
• Page End: 8210
• Publication Date: 2020-08-03
• Subjects: Aravalli Craton -- granite -- India -- magmatism -- tectonometamorphic history -- zircon geochronology; Geology -- Periodicals; 551
• DOI: 10.1002/gj.3927
• Languages: English
• ISSNs: 0072-1050

Abstract

Abstract : The Banded Gneissic Complex of the Aravalli Craton of northwestern India comprises Palaeo‐ to Neoarchaean (3.3–2.7 Ga) gneisses, including tonalite–trondhjemite–granodiorite (TTG) gneisses, intruded by Neoarchaean (2.6–2.5 Ga) TTGs, sanukitoids, and potassic granites. The latter include the Malola granite that crops out near Bhilwara and forms the basement for the Mesoproterozoic Pur‐Banera mineralized belt. The granite has experienced three deformation events, represented by an S1 foliation and superimposed open folds and dextral shears. Textural evidence and thermobarometry indicate that prograde metamorphism initially forming actinolite and subsequently diopside, and culminating in the upper amphibolite facies, was followed by retrograde metamorphism in the greenschist facies with fluid influx, forming zoisite. Zircon geochronology yields a crystallization age of 2, 538 ± 11 Ma and indicates a prominent metamorphic overprint in the region at 1, 307 ± 9 Ma. The Malola granite has low Sr–Nd isotopic ratios, enrichments in fluid‐mobile elements (Cs, Rb, Ba, Th, and Pb), and depletions in alteration‐resistant elements (Nb, Ta, and Ti). These characteristics combined with mineralogical evidence suggest that the granite was derived by anatexis of older crystalline crust (possibly granulitic lower crust) in the same subduction zone setting inferred previously for other Neoarchean granitoids in this region. Geochemical and Sr–Nd–Hf isotopic similarities between the Malola granite and Neoarchaean granitoids of the Aravalli, Bundelkhand, Bastar, Dharwar, and Congo cratons indicate a major role for anatectic crustal reworking in their genesis. Abstract :