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东昆仑大格勒一带基性二辉麻粒岩的变质演化及地质意义
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作者 李佳斌 吕增 +1 位作者 陈振宇 刘小辉 《岩石学报》 SCIE EI CAS CSCD 北大核心 2023年第9期2636-2650,共15页
基性麻粒岩作为高温变质作用产物,其矿物组合能够较好地记录区域地壳热流的峰值范围,是揭示造山带演化历史的重要窗口。本文报道了在东昆仑造山带东段大格勒地区金水口岩群副片麻岩中发现的基性二辉麻粒岩露头,它们呈块状-片麻状构造,... 基性麻粒岩作为高温变质作用产物,其矿物组合能够较好地记录区域地壳热流的峰值范围,是揭示造山带演化历史的重要窗口。本文报道了在东昆仑造山带东段大格勒地区金水口岩群副片麻岩中发现的基性二辉麻粒岩露头,它们呈块状-片麻状构造,斑状变晶-细粒变晶结构,主要矿物为斜长石、斜方辉石、单斜辉石、黑云母和普通角闪石。斜方辉石与单斜辉石和高钙斜长石(An=74~81)的平衡结构以及斜方辉石中包裹残余普通角闪石和黑云母的结构表明这些岩石经历了较充分的麻粒岩相结晶作用。填隙状生长的普通角闪石和黑云母可能代表了冷却至固相线附近矿物-残余熔体发生反应的产物。根据二辉石温度计和相平衡模拟计算,获得在0.4~0.7GPa压力条件下的麻粒岩相变质温度为840~910℃。详细的变斑晶斜长石和钛铁矿包体研究表明,麻粒岩相变质之前可能存在一期低温高压变质作用,形成的矿物组合为斜黝帘石+金红石+榍石+普通角闪石±阳起石+黑云母+石英,相平衡模拟确定该阶段的温压条件为0.85~1.2GPa、500~640℃。斜黝帘石在减压阶段的早期转变为低钙斜长石(An=46-51),同时角闪石转变为单斜辉石,可能代表了低压角闪岩相阶段。通过LA-ICPMS锆石U-Pb测年以及锆石包体分析,确定麻粒岩相变质年龄为411.4±2.9Ma(MSWD=1.05)。这些二辉麻粒岩是在金水口以外的东昆仑地区发现的首例晚古生代低压高温变基性岩,其与围岩片麻岩构成一个麻粒岩地体。它们反映了泥盆纪早期东昆仑造山带的异常高温事件,与后碰撞伸展阶段软流圈地幔上涌带来的区域高温热流有关。本研究对解析东昆仑造山带高级变质地体的精细结构以及古特提斯洋形成过程的深部动力学机制具有重要意义。 展开更多
关键词 二辉麻粒岩 P-T轨迹 锆石U-PB定年 低压高温变质作用 大格勒 东昆仑造山带
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High-pressure granulite from Western Kunlun,northwestern China:Its metamorphic evolution,zircon SHRIMP U-Pb ages and tectonic implication 被引量:8
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作者 QU JunFeng ZHANG liFei +4 位作者 AI Yongliang l zeng WANG JianPing ZHOU Hui WANG ShiYan 《Science China Earth Sciences》 SCIE EI CAS 2007年第7期961-971,共11页
High-pressure mafic granulites occurring as lenticular bodies within garnet-amphibolites in Kangxiwar Fault have been first reported in this paper. The P-T conditions of two metamorphic stages were obtained using cali... High-pressure mafic granulites occurring as lenticular bodies within garnet-amphibolites in Kangxiwar Fault have been first reported in this paper. The P-T conditions of two metamorphic stages were obtained using calibrated geothermal barometers and ThermoCalc Program. The peak metamorphic condition of these high-pressure granulites is about 760–820°C, 1.0–1.2 GPa and the retrograde metamorphic condition is about 620–720°C, 0.7–0.8 GPa. The petrological studies show that they have a near-isobaric cooling P-T path which suggests that the Western Kunlun underwent initial crustal thickening, subsequent exhumation and cooling. The SHRIMP zircon U-Pb dating gives two groups of ages for high-pressure granulites. One is 177±6 Ma which is obtained from the rim of the zircon. We consider this age should be the metamorphic age. And the other is 456±30 Ma which is obtained from the core of the zircon and should be the protolith age. The formation of these high-pressure granulites in western Kunlun is closely correlated with the evolution of the Paleo-Tethys and has important implications for the research on Tethys and Paleo-Asian tectonic zone. 展开更多
关键词 WESTERN KUNLUN Kangxiwar Fault high-pressure GRANULITE P-T path SHRIMP U-PB DATING of ZIRCON
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