MASSIVE GRANITOID PRODUCTION WITHOUT MASSIVE CONTINENTAL-CRUST GROWTH IN THE CHINESE ALTAY:INSIGHT INTO THE SOURCE ROCK OF GRANITOIDS USING INTEGRATED ZIRCON U-Pb AGE,Hf-Nd-Sr ISOTOPES AND GEOCHEMISTRY
作者单位：Key Laboratory of Mineral ResourcesInstitute of Geology and GeophysicsChinese Academy of Sciences State Key Laboratory of Lithospheric EvolutionInstitute of Geology and GeophysicsChinese Academy of Sciences
会议名称：《中国科学院地质与地球物理研究所2012年度（第12届）学术年会》
会议日期：2013年
学科分类：070902[理学-地球化学] 0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学]
关 键 词：Granitoid Chinese Altay non-massive continental-crust growth Hf-Nd-Sr isotopes zircon U-Pb age
摘 要：This study integrates new and extant zircon U-Pb age and Hf isotope data,whole-rock Nd-Sr isotope data,and geochemistry data from the Chinese Altay (CA) and adjacent areas,in an attempt to identify the source rocks of granitoids and acidic-intermediate volcanic rocks and,hence,continental-crust growth in the *** protolith of the gneisses includes the earliest products of erosion from the surface rocks of the island arc volcanics and the syn- and post-collisional granitoids of the Caledonian orogenic-mountain system,whereas the provenance of metasedimentary rocks was exposed from increasingly deeper levels or from an expanded region that evolved from the axis to the flank of the mountain system as it was denuded until planation such that eroded material from the Tuva-Mongol microcontinental block to the east could be delivered to the *** CA tends to be more mafic and isotopically more primitive with depth,because material eroded early constitutes the lower section and material eroded late constitutes the upper section of the Early-Paleozoic sedimentary -pile. Source rocks for the granitoids and acidic-intermediate volcanic rocks of the CA include the eroded material from the microcontinental block,the eroded material from the syn- and post-collisional granitoids of the Caledonian province,MORB-type mafic rocks,and a minor component from the metasomatized lithospheric-mantle. Eroded material from the terrains north of the CA was first deposited as an Early-Paleozoic sedimentary-pile in the *** top section of this pile was again eroded and transported to the trench at the CA continental margin,and these second-round sediments were subducted beneath the CA accretionary *** un-eroded lower section of the Early-Paleozoic sedimentary-pile lay at bottom of the CA accretionary wedge that was underplated by MORB-type mafic rocks. The CA granitoids can be divided into orogenic(460-360 Ma) and post-orogenic (～320-260 Ma).The orogenic granitoids can be subdivided