A new cache of Eoarchaean detrital zircons from the Singhbhum craton,eastern India and constraints on early Earth geodynamics  

作　　者：Bulusu Sreenivas Sukanta Dey Y.J. Bhaskar Rao T. Vijaya Kumar E.V.S.S.K. Babu Ian S. Williams 

机构地区：[1]CSIR-National Geophysical Research Institute,Hyderabad 500007,India [2]Department of Earth Sciences,Indian Institute of Science Education and Research,Kolkata 741246,India [3]Research School of Earth Sciences,The Australian National University,Canberra 2601,Australia

出　　处：《Geoscience Frontiers》2019年第4期1359-1370,共12页地学前缘（英文版）

基　　金：Financial support from the Ministry of Earth Sci-ences,New Delhi for Excimer 193 nm LA system at CSIR-NGRI MoES/P.O.(Seismo)/1(245)/2014;for the project on Singhbhum craton to S.D.,E.V.S.S.K.B.,B.S.and T.V.K(No.MoES/P.O.(Geosci)45/2015;GAP-738-28EVB);part of the CSIR-NGRI projects INDEX(PSC0204) and GEOMET

摘　　要：The dominant geodynamic processes that underpin the formation and evolution of Earth’s early crust remain enigmatic calling for new information from less studied ancient cratonic nuclei.Here,we present U-Pb ages and Hf isotopic compositions of detrital zircon grains from^2.9 Ga old quartzites and magmatic zircon from a 3.505 Ga old dacite from the Iron Ore Group of the Singhbhum craton,eastern India.The detrital zircon grains range in age between 3.95 Ga and 2.91 Ga.Together with the recently reported Hadean,Eoarchean xenocrystic(up to 4.24 Ga)and modem detritus zircon grains from the Singhbhum craton,our results suggest that the Eoarchean detrital zircons represent crust generated by recycling of Hadean felsic crust formed at^4.3-4.2 Ga and^3.95 Ga.We observe a prominent shift in Hf isotope compositions at^3.6-3.5 Ga towards super-chondritic values,which signify an increased role for depleted mantle and the relevance of plate tectonics.The Paleo-,Mesoarchean zircon Hf isotopic record in the craton indicates crust generation involving the role of both depleted and enriched mantle sources.We infer a short-lived suprasubduction setting around^3.6-3.5 Ga followed by mantle plume activity during the Paleo-,Mesoarchean crust formation in the Singhbhum craton.The Singhbhum craton provides an additional repository for Earth’s oldest materials.The dominant geodynamic processes that underpin the formation and evolution of Earth’s early crust remain enigmatic calling for new information from less studied ancient cratonic nuclei.Here,we present U-Pb ages and Hf isotopic compositions of detrital zircon grains from ～2.9 Ga old quartzites and magmatic zircon from a 3.505 Ga old dacite from the Iron Ore Group of the Singhbhum craton,eastern India.The detrital zircon grains range in age between 3.95 Ga and 2.91 Ga.Together with the recently reported Hadean,Eoarchean xenocrystic(up to 4.24 Ga)and modem detritus zircon grains from the Singhbhum craton,our results suggest that the Eoarchean detrital zircons represent crust generated by recycling of Hadean felsic crust formed at ～4.3-4.2 Ga and ～3.95 Ga.We observe a prominent shift in Hf isotope compositions at～3.6-3.5 Ga towards super-chondritic values,which signify an increased role for depleted mantle and the relevance of plate tectonics.The Paleo-,Mesoarchean zircon Hf isotopic record in the craton indicates crust generation involving the role of both depleted and enriched mantle sources.We infer a short-lived suprasubduction setting around～3.6-3.5 Ga followed by mantle plume activity during the Paleo-,Mesoarchean crust formation in the Singhbhum craton.The Singhbhum craton provides an additional repository for Earth’s oldest materials.

关 键 词：U-PB ZIRCON ages Hf isotopes SINGHBHUM CRATON HADEAN Eoarchean GEODYNAMICS 

分 类 号：P[天文地球]