义敦岛弧带稻城贡巴纳过铝质花岗岩成因及构造意义Petrogenesis and Tectonic Implication of Gongbana,Daocheng,Peraluminous Granitoids in Yidun Island Arc Belt
杨海军;肖龙;吴涛;杨钢;
摘要(Abstract):
稻城贡巴纳岩体位于义敦岛弧碰撞造山带的南东侧。采用LA-ICP-MS的方法研究了贡巴纳岩体,结果表明岩体锆石LA-ICP-MS U-Pb表面年龄为(226.7±2.8)Ma,是印支期岩浆活动的产物。岩性组合复杂,在岩相学特征上,呈浅灰-灰白色,暗色矿物含量低,并出现褐帘石等富铝矿物。岩石地球化学特征显示:高w(SiO2)=71.24%~73.86%,低MgO、FeOT、CaO,ALK=6.47%~6.86%,A/CNK=1.04~1.07,δ=1.36~1.57,AR=4.43~4.90,属于高钾钙碱性系列过铝质花岗岩。相对富集大离子亲石元素,贫化高场强元素;Rb/Sr=0.71~0.88,w(∑REE)=159.3×10-6~190×10-6,轻稀土元素相对富集,轻重稀土元素的分馏比值较高La/Yb=12.87~16.54,δEu=0.16~0.18,总体表现为右倾型,显示与Ⅰ型花岗岩的特征相似。根据花岗岩的R1-R2,Nb-Y构造环境判别图解及区域构造演化史研究,认为该岩体形成于同碰撞构造环境,其形成与义敦岛弧带俯冲碰撞造山活动有关,即三江古特提斯洋闭合事件对接时间为三叠纪。
关键词(KeyWords): 过铝质Ⅰ型花岗岩;锆石U-Pb定年;地球化学;岩石成因;构造意义;稻城贡巴纳
基金项目(Foundation): 国家自然科学基金项目“青藏高原中部昆仑-巴颜喀拉-金沙江古特提斯构造岩浆演化及动力学”(1212011121270)
作者(Author): 杨海军;肖龙;吴涛;杨钢;
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