Transition from oceanic subduction to continental collision:Insights from volcanogenic-sedimentary rocks of the Tannuola terrane(northern Central Asian Orogenic Belt)  

作　　者：E.V.Vetrov N.I.Vetrova 

机构地区：[1]V.S.Sobolev Institute of Geology and Mineralogy SB RAS,Koptyuga ave.3,Novosibirsk,Russia

出　　处：《Geoscience Frontiers》2024年第4期41-60,共20页地学前缘（英文版）

基　　金：funded by a grant from the Russian Science Foundation(project No 22-77-10069;geochronological and geochemical studying)and by state assignment of IGM SB RAS(No122041400214-9,fieldwork).

摘　　要：Magmatism associated with oceanic subduction plays a dominant role in crustal growth during the Earth's evolution.The Tannuola terrane,situated in the northern Central Asian Orogenic Belt(CAOB),is a key area to understanding oceanic subduction and initial collision processes in the northern CAOB.In order to investigate the switch from subduction to collision settings,detailed field mapping,zircon SHRIMP U-Pb geochronological and whole-rock geochemical studies of volcanogenic-sedimentary rocks from the Tannuola terrane were carried out.Zircon U-Pb ages indicate multi-stage volcanism lasted at least 30 Ma from~540 to~510 Ma,that can be divided into three events:the late Ediacaran(before~540 Ma),the early Cambrian(~520 Ma)and the middle Cambrian(~510 Ma).These ages are inter-preted to the initial,main and final stages of oceanic subduction during the late Proterozoic-early Paleozoic.During the late Ediacaran,tholeiitic basalts with highεNd(t)values(from+7.4 to+8.5)were emplaced.Likely forming by the 10%-30%partial melting of spinel-garnet mantle source during slab subduction.During the early Cambrian,transitional from tholeiitic to calc-alkaline basaltic rocks withεNd(t)value(+5.6)and coeval intermediate-felsic volcanic rocks with similarεNd(t)values(+5.9 and+6.5)formed.The early Cambrian basaltic rocks are interpreted to be derived by 10%-30%partial melt-ing of a depleted mantle source metasomatized by slab-derived fluids released from the subducting ocea-nic slab.The middle Cambrian calcalkaline basaltic rocks withεNd(t)value of+6.2 might be emplaced as a result of low(5%-10%)degree partial melting of a metasomatized mantle followed by fractional crys-tallization of clinopyroxene and plagioclase.Associated intermediate-felsic volcanic rocks withεNd(t)values from+6.0 to+6.8 were formed through fractionation of the juvenile Neoproterozoic sources.The middle Cambrian volcanism is interpreted to be triggered by the slab break-off during the transition to a collisional setting.

关 键 词：Island-arc magmatism EDIACARAN CAMBRIAN zircon U-Pb dating Nd isotopes Central asian orogenic belt 

分 类 号：P542[天文地球—构造地质学] P588.121[天文地球—地质学]