西天山伊犁山间坳陷二叠系乌郎组玄武岩地球化学特征及构造环境判别  

Geochemical Characteristics and Tectonic Setting of the Basalt of Permian Wulang Formation in the Yili Intermountain Depression,Western Tianshan

作　　者：杨德敏[1] 刘陈明[1] 王明 杜勇 马伟[1] 唐娇[1] 刘德利[1] Yang Demin;Liu Chenming;Wang Ming;Du Yong;Ma Wei;Tang Jiao;Liu Deli(Yunnan Vocational College of Land and Resources,Kunming,Yunnan,650093,China;No.8 Geological Team,Xingjiang Geology and Mineral Resources Development Bureau,Aksu,Xingjiang,843000,China)

机构地区：[1]云南国土资源职业学院,云南昆明650093 [2]新疆维吾尔自治区地质矿产勘查开发局第八地质大队,新疆阿克苏843000

出　　处：《新疆地质》2023年第3期307-314,共8页Xinjiang Geology

基　　金：云南省教育厅科学研究基金项目(2018JJ569);新疆西天山1∶5万K44E004019、K44E004020、K44E005020三幅区域地质矿产调查项目(T15-1-LQ05)共同资助。

摘　　要：西天山二叠纪构造演化对哈萨克斯坦-准噶尔板块与塔里木-华北板块重建具重要意义,目前对该时期西天山构造环境认识存在争议。通过对新源县山口水电站东剖面乌郎组开展实测剖面研究发现,剖面包含玄武岩-凝灰岩-砂岩等,表现出溢流相-喷发相-沉积相组合,具5个火山喷发韵律等,表明该地区乌郎组形成于陆缘环境。通过对乌郎组玄武岩主量、微量、稀土元素进行分析发现,样品里特曼指数(σ)为1.6~6.71,AR为1.28~1.97,为钙碱-碱性准铝质玄武岩;ΣREE为-88.21×10^(-6)~285.73×10^(-6),LR/HR为3.31~6.49,属轻稀土富集型玄武岩。(Rb/Yb)_(N)为3.04~4.61,Nb/Ta为20.70~40.83,Zr/Hf为16.09~64.58,为受陆壳、火山弧影响交代地幔源残余玄武岩。通过Sm/Yb-Sm图解分析发现,火山岩浆对应俯冲深度可能起源于上地幔120~150km。据玄武岩源区特征判别岩浆物源为石榴石二辉橄榄岩带,深度熔融。结合区域以往研究和Hf/3-Th-Ta图解认为,该地区乌郎组形成于陆缘岛弧环境。The Permian tectonic evolution of the Western Tianshan Mountains is significance for the reconstruction of the Kazakhstan Junggar plate and the Tarim North China plate,but there is a dispute on the understanding of the tectonic environment of the Western Tianshan Mountains during this period.Based on the field survey of Wulang Formation in the east section of Shankou Hydropower Station,this paper found that the profile contains basalt,tuff,sandstone,showing the combination of overflow-eruption-sedimentary,with five volcanic eruption rhythms,indicating that the Wulang Formation in this area was formed in a continental margin environment;The major,trace and rare earth elements analysis study of basalts show that the sample Littman index 1.6~6.71,AR 1.28~1.97,calc-alkaline,alkaline para aluminous basalt.ΣREE 88.21×10^(-6)~285.73×10^(-6),LR/HR3.31~6.49,light rare earth enriched basalt.(Rb/Yb)_(N)3.04~4.61,Nb/Ta 20.70~40.83,Zr/Hf16.09~64.58,which are residual basalts of metasomatic mantle source affected by continental crust and volcanic arc.Through Sm/Yb-Sm graphic analysis,it is found that the corresponding subduction depth of volcanic magma may originate from the upper mantle 120~150km.According to the characteristics of basalt source area,the magma material source is garnet lherzolite belt,with a high depth melting;Combined with previous regional studies and Hf/3-Th Ta diagram,it is believed that the Wulang Formation in this area was formed in a continental edge island arc environment.

关 键 词：乌郎组 玄武岩 地球化学 构造环境 陆缘岛弧 

分 类 号：P588.145[天文地球—岩石学] P59[天文地球—地质学]