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

详细信息	查看全文 | 推荐本文 |

• 作者：C. Manikyamba^a ; ^{cmaningri@yahoo.com} ; Robert Kerrich^b
• 关键词：Continental lithosphere growth ; Zoned plume ; Subduction-accretion ; Neoarchean mantle ; Geodynamics ; Eastern Dharwar Craton
• 刊名：Geoscience Frontiers
• 出版年：2012
• 期刊代码：pc98_16749871
• 类别：ear
• 出版时间：May, 2012
• 卷：3
• 期：3
• 页码：225-240
• 文件大小：1489 K

摘要

Greenstone belts of the eastern Dharwar Craton, India are reinterpreted as composite tectonostratigraphic 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聽km under thin rifted continental lithosphere to preserve intraoceanic and continental margin aspects. Associated alkaline basalts record subduction-recycling of Mesoarchean 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 Phanerozoic 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 compositionally 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聽Ma), hot, oceanic lithosphere. Consequently, Cenozoic style 鈥渉ot鈥?subduction was operating in the Neoarchean. These diverse volcanic associations were assembled to give composite terranes in a subduction-accretion orogen at 鈭?.7聽Ga, coevally with a global accretionary orogen at 鈭?.7聽Ga, and associated orogenic gold mineralization.

Archean lithospheric mantle, distinctive in being thick, refractory, and buoyant, formed complementary to the accreted plume and convergent margin terranes, as migrating arcs captured thick plume-plateaus, and the refractory, low density, residue of plume melting coupled with accreted imbricated plume-arc crust.