Neoproterozoic Multi-Terrane Convergence in South China and Its Resource Implications
[Objective]The Neoproterozoic Era marks a crucial period for continental generation,reworking,and re-shaping of the South China Block(including the Yangtze Block to the northwest and Cathaysia Block to the south-east).However,Neoproterozoic rocks are widely developed in the block and constitute the leading basement sequenc-es of Phanerozoic rocks and ore deposits.Studying the formation of Neoproterozoic rocks and crustal construction pro-cesses of the South China Block is important for exploring regional resources and environment impacts,the assembly and dispersal behaviors of Neoproterozoic supercontinents and the subsequent"Cambrian explosion."[Methods]Here,we reviewed key geological records in the South China Block during the Early-to-Middle Neoproterozoic and suggested the existence of a multi-terrane(or multi-microcontinent)structure in South China and nearby regions dur-ing the Neoproterozoic.[Results and Conclusions]This multi-terrane structure may have paved the way for a long-lived ocean-continent interaction in Neoproterozoic South China,as well as consequent arc magmatism,subduction-zone metamorphism,and terrane accretion.Furthermore,the terrane/microcontinent boundaries could be roughly de-fined by a series active-and passive-continent-margin rock units.Specifically,we speculated the multi-terrane struc-ture was established in the Late Mesoproterozoic and persisted during the Early-to-Middle Neoproterozoic.This con-clusion is based on the occurrence of a series of Late Mesoproterozoic to Neoproterozoic oceanic lithosphere relics,in-cluding island arc rocks(e.g.,Dahongshan,Tongmuliang,Changba,Shuangxiwu arcs)and ophiolites(e.g.,Shimi-an,Miaowan,Huashan,Sanchazi and northeastern Jiangxi ophiolites).Late Mesoproterozoic continent passive-margin sedimentary rocks(e.g.,Shennongjia,Macaoyuan,Kunyang,and Huili Group)that are extensively preserved in the South China Block may correspond to a successful continental rift and support a multi-terrane struc-ture.In the Early Neoproterozoic,we suggest passive continental margins transitioned active ones,and extensive convergent processes operated within the South China Block and its nearby regions.This conclusion is supported:(1)linearly-distributed continental-arc calc-alkaline magmatism along western and northern Yangtze margins(i.e.,the Panxi-Hannan Belt);(2)rapid endogenic recycling processes induced by ocean-continent subduction recorded in the Huangshuihe migmatites;(3)a range of 880-750 Ma subduction-zone metamorphism reported in the Panxi-Hannan Belt and South Qinling;(4)Neoproterozoic extrusion-related deformation documented within the basement sequences of the Jiangnan orogen,southeastern Yangtze margins;(5)numerous accretionary rock complexes from the Neoproterozoic that witnessed accretion of oceanic sediments and arcs,ophiolites,outboard terrane(e.g.,eastern Jiangnan orogen,Dahongshan Group and Huangshuihe Group,Changba complex).In this regard,we propose the South China Block experienced a prolonged Neoproterozoic accretionary orogeny and consequent terrane/microcontinent amalgamation,accompanied by possible outward migration and reorganization of active continental margins.These Neoproterozoic subduction-accretion processes played an important role in shaping the current South China Block.More importantly,these Neoproterozoic terrane-boundary domains could be major sites for Phanerozoic crustal differentiation and element recycling that led to the formation of a range of ore deposits within the South China Block.For example,W-Sn and rare earth ores in southern Hunan and southern Jiangxi provinces situate in boundary domains between Nanling-Yunkai and Wuyi terranes.Additionally,W and Cu-Au ores in northeastern Jiangxi province are located at boundary domains between Huaiyu terrane and southeastern Yangtze margin.This potential connection between Neoproterozoic basement and Phanerozoic ore-forming processes requires further investigation in the future.
South China BlockNeoproterozoicsubduction-accretionmulti-terrane convergenceresource implication
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维普
