青海沱沱河地区扎拉夏格涌粗面岩锆石U-Pb年代学及地球化学特征  

Zircon U-Pb chronology and geochemistry of Zhalaxiageyong trachyte in Tuotuohe area,Qinghai

作　　者：宁传奇 李碧乐[1] 王斌[2] 王国志[1] 杨文龙[1] NING Chuan-qi LI Bi-le WANG Bin WANG Guo-zhi YANG Wen-long(College of Earth Sciences, Jilin University, Changchun 130061, China No. 5 Exploration Team of Hebei Geological and Prospecting Bureau, Tangshan 063004, Hebei, China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]河北地勘局第五地质大队,河北唐山063004

出　　处：《世界地质》2016年第4期920-930,共11页World Geology

基　　金：青海沱沱河整装勘查区富铅锌矿成矿规律及富矿体找矿部署研究(12120114080901)资助

摘　　要：对青海沱沱河地区扎拉夏格涌粗面岩进行U--Pb年代学和地球化学特征研究,结果表明：扎拉夏格涌粗面岩锆石U--Pb年龄为32.39-34.06 Ma,加权平均年龄为（33.09±0.26）Ma,形成时代为渐新世;岩石属于高硅高钾准铝质-过铝质钾玄岩系列。稀土元素配分模式图呈右倾型,轻重稀土元素分馏明显[（La/Yb）N=19.96-34.00,平均值26.99],弱铕正异常（δEu=1.00-1.20,平均值1.08）;样品富集大离子亲石元素（LILE：Rb,Ba,K）,亏损高场强元素（HFSE：Nb,Ta,P,Ti）,高场强元素Zr,Th较富集。岩石具有C型埃达克岩特征,为新生镁铁质下地壳部分熔融产物。通过区域对比和总结前人研究成果,认为扎拉夏格涌粗面岩形成于新生代早期造山加厚之后的伸展阶段。The authors studied the characteristics of U--Pb chronology and geochemistry of trachyte in Zhalaxiageyong of Tuotuohe area,Qinghai.The results show that the zircon U--Pb age is 32.39 - 34.06 Ma,with weighted average age of（33.09 ± 0.26） Ma,which indicate the trachyte formed in Oligocene.The rock belongs to high-SiO2,high-K peraluminous-metaluminous shoshonite series.The REE pattern appears rightward sloping with significant fractionation of LREE and HREE [（La/Yb）N= 19.96 - 34.00,mean = 26.99],with slight positive Eu anomalies（δEu = 1.00 - 1.20,mean = 1.08）.The samples are characterized by enrichment in large ion lithophile elements（LILEs：e.g.Rb,Ba,K）,depletion in high field strength elements（HFSEs：e.g.Nb,Ta,P,Ti）,but HFSEs Th and Zr are richer.The rock has the characteristics of C-type adakite,as a new product of the partial melting of mafic lower crust.On the basis of the previous research results in combination with regional comparison,it is considered that Zhalaxiageyong trachyte formed in extensional stage after orogenic thickening in Early Cenozoic.

关 键 词：青海 沱沱河地区 扎拉夏格涌 粗面岩 锆石U-PB年龄 年代学 地球化学 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]