东昆仑东段浪木日上游早古生代榴辉岩的发现及其意义

发布时间：2018-03-06 20:28

本文选题：东昆仑东段　切入点：高压变质　出处：《地质通报》2016年11期 　论文类型：期刊论文

【摘要】：在东昆仑东段郎木日上游最新识别出榴辉岩,其野外产状为透镜状、块状,与围岩呈断层接触。含榴辉岩的变质带宽1~3km,榴辉岩呈透镜体状分布于古元古界白沙河岩组变质岩及新元古代花岗片麻岩中,榴辉岩相岩石组合为榴辉岩和榴闪岩。榴辉岩相矿物组合为石榴子石+绿辉石+金红石+石英。石榴子石-单斜辉石矿物温压计估算出榴辉岩形成的温压条件为T=650~750℃,p=1.8~2.0GPa,在石榴子石Alm+Spess-Pyr-Gross三角图解中落入C型榴辉岩区。榴辉岩中锆石阴极发光图像显示,大部分具有扇形分带或杉树叶结构,少数具有弱环带结构,31颗锆石Th/U值较低(0.06~0.135),其LA-ICP-MS锆石U-Pb年龄明显分为2类,一类谐和年龄值为431.9±2.3Ma,代表了榴辉岩相峰期变质年龄;另一类谐和年龄值为487±5.9Ma,可能为原岩在俯冲过程中受构造热事件影响发生变质的结果。参考区域蛇绿岩及构造岩浆事件,确定研究区本次高压变质的峰期时代为早志留世晚期,可能发生于东昆仑俯冲消减-碰撞环境,结合邻区发现的同类型榴辉岩,恢复了一条东昆仑地区早古生代的高压变质带。
[Abstract]:Eclogites have been recently identified in the upper reaches of Langmuri, East Kunlun. The eclogite occurs lenticular and massive in the field. The metamorphic bandwidth of eclogite is 1 ~ 3 km, and eclogite is distributed in the paleoproterozoic Baishaheyan formation metamorphic rocks and Neoproterozoic granitic gneiss, and the metamorphic rocks of the paleoproterozoic Baishaheyan formation and the Neoproterozoic granitic gneiss. The eclogite facies rock assemblage consists of eclogite and eclogite. The eclogite facies mineral assemblage is pomegranate alopyroxene rutile quartz. The temperature and pressure conditions of eclogite and clinopyroxene minerals are estimated as follows:. In the Alm Spess-Pyr-Gross triangle diagram of pomegranate, it fell into the C eclogite area. The cathodoluminescence image of zircon from eclogite shows that the zircon of the eclogite falls into the C type eclogite area. Most of them have fan-shaped zonation or fir leaf structure, and a few have weak annular structure. The Th/U value of 31 zircons is lower than 0.06 ~ 0.135. The U-Pb age of LA-ICP-MS zircon is obviously divided into two categories, and the harmonic and age values are 431.9 卤2.3 Ma, which represent the metamorphic age of eclogite facies. The other kind of harmonic age is 487 卤5.9 Ma, which may be the result of metamorphism caused by tectonic thermal events during subduction. Referring to the regional ophiolite and tectonic magma events, the peak age of this high-pressure metamorphism in the study area is determined to be the late early Silurian period. A high-pressure metamorphic zone of early Paleozoic in East Kunlun region was restored by combining the same type of eclogite discovered in adjacent area in the subduction subduction collisional environment of East Kunlun Mountains.
【作者单位】：中陕核工业集团地质调查院有限公司;长安大学地球科学与资源学院;中国地质科学院地质研究所;
【基金】：中国地质调查局项目(编号:12120113028500)
【分类号】：P588.3

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