Eastern Dharwar Craton, India： Continental lithosphere growth by accretion of diverse plume and arc terranes

• Published in: Di xue qian yuan. 2012-05, Vol.3 (3), p.225-240
• Main Authors: Manikyamba, C., Kerrich, Robert
• Format: Article
• Language: English
• Subjects: Continental lithosphere growth; Eastern Dharwar Craton; Geodynamics; Marine; Neoarchean mantle; Subduction-accretion; Zoned plume; 印度; 地体; 地块; 增生; 大陆岩石圈; 拉斑玄武岩; 洋壳俯冲; 碱性玄武岩
• ISSN: 1674-9871
• DOI: 10.1016/j.gsf.2011.11.009

Abstract Greenstone belts of the eastern Dharwar Craton, India are reinterpreted as composite tecto- nostratigraphic terranes of accreted plume-derived and convergent margin-derived magmatic sequences based on new high-precision elemental data. The former are dominated by a komatiite plus Mg-tholeiitic basalt volcanic association, with deep water siliciclastic and banded iron formation （BIF） sedimentary rocks. Plumes melted at 〈90 km under thin rifted continental lithosphere to preserve intrao- ceanic and continental margin aspects. Associated alkaline basalts record subduction-recycling of Me- soarchean oceanic crust, incubated in the asthenosphere, and erupted coevally with Mg basalts from a heterogeneous mantle plume. Together, komatiites-Mg basalts-alkaline basalts plot along the Phanero- zoic mantle array in Th/Yb versus Nb/Yb coordinate space, representing zoned plumes, establishing that these reservoirs were present in the Neoarchean mantle. Convergent margin magmatic associations are dominated by tholeiitic to calc-alkaline basalts compo- sitionally similar to recent intraoceanic arcs. As well, boninitic flows sourced in extremely depleted mantle are present, and the association of arc basalts with Mg-andesites-Nb enriched basalts-adakites documented from Cenozoic arcs characterized by subduction of young （〈20 Ma）, hot, oceanic litho- sphere. Consequently, Cenozoic style ＂hot＂ subduction was operating in the Neoarchean. These diverse volcanic associations were assembled to give composite terranes in a subduction-accretion orogen at -2.7 Ga, coevally with a global accretionary orogen at -2.7 Ga, and associated orogenic gold mineralization.