Early growth of the Indian lithosphere: Implications from the assembly of the Dharwar Craton and adjacent granulite blocks, southern India

• Published in: Precambrian research Vol. 336; p. 105491
• Main Authors: Ratheesh-Kumar, R.T., Windley, B.F., Xiao, W.J., Jia, X-L., Mohanty, D.P., Zeba-Nezrin, F.K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2020
• Subjects: Arc magmatism; Charnockite; High-grade terrane; Metamorphism; Subduction; Zircon geochronology; Charnockite; Arc magmatism; Metamorphism; Subduction; Zircon geochronology; High-grade terrane
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2019.105491

•New insights into the geodynamic evolution of the Biligiri Rangan Block (BRB).•The BRB charnockites and mafic granulites evolved by Neoarchean arc magmatism.•Melting of ca. 3400–3200 Ma BRB protolith to form charnockites at ca. 2700–2500 Ma.•Similar arc magmatic evolution of charnockites in the Nilgiri and Coorg Blocks.•Closure of the Paleo-Dharwar Ocean and assembly of the Dharwar Craton. This study provides a new perspective into the Archean accretionary tectonic evolution of the Dharwar Craton and the adjacent high-grade granulite blocks of southern India. The necessary constraints for this tectonic assembly were derived using new petrochemical and zircon U-Pb age data from the granulite facies Biligiri Rangan Block (BRB), which occupies a central key position in the Archean collage of southern India. The BRB, composed largely of charnockites and mafic granulites, is a vestige of ca. 3400–3200 Ma cratonic fragment that was amalgamated with the Western Dharwar Craton (WDC) at ca. 2700–2500 Ma. The spatial variations in composition and evolution of the charnockites (i.e. low- and high-Sr/Y variants) are attributed to arc magmatic processes at different crust-mantle depths accompanied by a flat- or shallow-dipping subduction geometry. Different stages in the subduction processes such as exhumation and magma underplating (ca. 2800–2950 Ma), initial arc magmatism (ca. 2700–2650 Ma), and peak magmatism together with metamorphism (ca. 2700–2500 Ma) were identified from zircon age populations of different rock-types. Our new results integrated with all published geological and geophysical data lead to the conclusion that the Kollegal and Mettur Shear Zones on the western and eastern sides of the BRB respectively were sited on an east-dipping Archean suture and a closed back-arc basin. We propose a tectonic model for southern India according to which subduction-accretion of the Coorg Block in the Mesoarchean (ca. 3300–3100 Ma) and of the Nilgiri Block, Biligiri Rangan Block and the Eastern Dharwar Craton in the Neoarchean (ca. 2700–2500 Ma) led to closure of the Paleo-Dharwar Ocean and to terminal collision with the Western Dharwar Craton.