云南中甸格咱地区晚三叠世火山岩年代学、地球化学特征及其构造意义

发布时间：2018-05-15 18:59

本文选题：晚三叠世 + 年代学　；参考：《岩石学报》2017年08期

【摘要】：位于义敦岛弧南端的中甸弧地区在印支期内发育大规模酸性-中酸性岩浆活动。近年来,前人对该地区做了大量的研究,但主要着眼于侵入岩,对火山岩的研究偏少。本文对分布于滇西北中甸格咱地区的中酸性火山岩进行锆石U-Pb定年、地球化学及Hf同位素分析,2件样品的锆石U-Pb年龄变化于214~212Ma,表明其为晚三叠岩浆活动的产物。岩石Si O2含量为53.37%~63.77%,全碱含量达5.19%~7.16%,为高钾钙碱性系列,富集大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ti等高场强元素,具有典型岛弧火山岩特征。所测锆石εHf(t)值介于-0.04~3.06之间,大部分为正值,显示出幔源岩浆特征,相对应的锆石Hf同位素二阶模式年龄为1.05~1.25Ga。综合岩石学、地球化学及构造地质特点认为,格咱火山岩形成于印支期甘孜-理塘洋壳西向俯冲构造背景,其源区为俯冲流体交代的岩石圈地幔,岩浆上升过程经历了壳源沉积物质混染。
[Abstract]:The Zhongdian arc region, located at the southern end of the Yun island arc, developed large-scale acid medium acidic magmatic activity during the Indosinian period. In recent years, a large number of previous studies have been done in this area, but the main focus is on intrusive rocks and less research on volcanic rocks. This paper made zircon U-Pb dating of the middle acidic volcanic rocks in the Zhongdian Ge Zan area, Northwest Yunnan. The zircon U-Pb age of 2 samples of 2 samples changes in 214~212Ma, indicating that it is a product of late three superposition of magma. The content of Si O2 in the rock is 53.37%~63.77%, the total alkali content is 5.19%~7.16%, it is a high potassium calc alkaline series, rich in large ion lithospheric elements and light dilute soil elements, and has a loss of Nb, Ta, Ti and other high field strength elements. The characteristics of island arc volcanic rocks. The measured value of the zircon Hf (T) is between -0.04~3.06, most of which is positive, showing the characteristics of mantle derived magma. The corresponding two order model age of zircon Hf isotopes is 1.05~1.25Ga. comprehensive petrology. The geochemistry and tectonic geological characteristics believe that the GEZAN volcanic rocks formed in the Western subduction of the Ganzi Litang ocean crust in the Indo Chinese period. The source area is the lithospheric mantle of subduction fluid metasomatism, and the process of magma rise has undergone a mixture of crustal deposits.

【作者单位】：中国地质大学地球科学与资源学院;中国人民武装警察部队黄金第七支队;
【基金】：国家重点基础研究发展规划项目(2015CB452604、2011CB403102) 国家重点研发计划项目(2016YFC0600502) 中国地质调查局综合研究项目(1212011220920)联合资助
【分类号】：P588.14

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