Petrogenesis of Early Carboniferous Alkaline Basalt from the Wusun Mountain:Implications for Tectonic Evolution of the Western Yining Block,NW China  

作　　者：WANG Zuopeng LV Yan LI Hai LI Yongjun ZHOU Yanlong LI Ganyu YANG Gaoxue 

机构地区：[1]School of Geological Engineering and Geomatics,Chang'an University,Xi'an 710054,China [2]School of Earth Science and Engineering,Xi'an Shiyou University,Xi'an 710054,China [3]School of Earth Science and Resources,Chang'an University,Xi'an 710054,China [4]Hebei GEO University,Shijiazhuang 050031,China

出　　处：《Acta Geologica Sinica(English Edition)》2021年第4期1128-1138,共11页地质学报（英文版）

基　　金：financially supported by the Fundamental Research Funds for the Central Universities,CHD(Grant Nos.300102271403,300102261401 and 300102261403);the National Natural Science Foundation of China(Grant No.41672285)。

摘　　要：Late Paleozoic volcanic rocks are well exposed in the Yining Block,NW China,and are predominately composed of andesites,rhyolites and volcaniclastics as well as minor basalts.Study of the petrology,whole-rock geochemistry and zircon U-Pb dating for the Early Carboniferous alkaline basalts from Wusun Mountain,western Yining Block,constrains their petrogenesis and tectonic evolution.The alkaline basalts consist mainly of plagioclases,mostly albite and labradorite,as well as clinopyroxenes and olivines;zircon U-Pb dating indicates their formation at ca.350 Ma.Geochemically,the basaltic samples have low SiO_(2)contents,and high TiO_(2),Al_(2)O_(3)and alkaline contents,coupled with high Na_(2)O/K_(2)O ratios,displaying an alkaline basalt affinity.They show remarkable LILE enrichment and HFSE depletion.Meantime,these samples have relatively high TFe_(2)O_(3),MgO,and Mg#values as well as Ni and Cr,relatively high Sm/Yb and U/Th,suggesting origination from a mantle source metasomatized by slab fluids.They formed in a transitional tectonic setting from arc to intraplate,showing a typical affinity of back-arc basin basalts.The alkaline basalts were likely generated in a nascent back-arc extension setting resulting from slab rollback of the southern Tianshan oceanic lithosphere.A bidirectional subduction model seems more reasonable for the evolution of the southern Tianshan Ocean.These new data will provide a new tectonic model for Late Paleozoic tectonic evolution of the western Yining Block.

关 键 词：PETROLOGY geochemistry isotopic dating alkaline basalt slab rollback Yining Block CAOB 

分 类 号：P534.45[天文地球—古生物学与地层学] P588.245[天文地球—地质学]