ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    西藏孔隆乡地区典中组火山岩年代学、 地球化学特征及构造意义

    Chronology, Geochemistry and Geological Significance of Volcanic Rocks of Dianzhong Formation in Konglong Township Area, Xizang

    • 摘要: 笔者对冈底斯中段孔隆乡地区典中组火山岩进行了年代学与地球化学研究。西藏孔隆乡地区典中组火山岩为一套酸性、弱铝质的高钾钙碱性岩石,富集大离子亲石元素Rb、K、U等,亏损高场强元素Nb、P和Ti,具有明显的壳源岩浆的特征,可能是地壳不同程度重熔作用的产物。根据该火山岩地球化学特征,推测其形成于火山弧构造环境,并且有向同碰撞及板内环境过渡的趋势。笔者获得流纹质凝灰岩样品的LA−ICP−MS锆石U−Pb年龄为(62.70±0.83)Ma,指示其形成时代为古近纪古新世。通过对比分析,该套火山岩喷发在冈底斯中西部要早于东部,印证了印度−亚洲大陆碰撞的穿时性这一观点。

       

      Abstract: In this paper, the chronology and geochemistry of the volcanic rocks of the Dianzhong Formation in the Konglong Township area of the central Gangdise are studied. The volcanic rocks of the Dianzhong Formation in Konglong Township Xizang are is a set of acidic, peraluminous, high-potassium, calcium-alkaline rocks, which are rich in large ion lithophile elements(e.g., Rb, K, U), and are depleted of high field strength elements (e.g., Nb, P, Ti), showing obvious characteristics of crust-derived magma, which may be the product of different degrees of remelting of the earth's crust.According to the geochemical characteristics of this volcanic rock, it is speculated that it was formed in a volcanic arc structural environment and has a tendency to transition to syn-collision and intraplate environment. The study samples are all rhyolite tuffs, and one sample obtained LA-ICP-MS zircon U-Pb age of 62.70±0.83 Ma, indicating that its formation age is the Paleogene Paleocene. Through comparative analysis, this set of volcanic rocks erupted earlier in the central and western Gangdise than in the east, confirming the view that the India-Asian collision is time-lapse.

       

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