中缅边界那邦变质基性岩的两期变质作用及其构造意义  

Study on Metamorphism of Granulitefacies MetamorphicRocks Discovered in the Nabang Area on the Border between China and Burma

作　　者：季建清[1] 钟大赉[1] 丁林[1] 韩秀伶[1] 

机构地区：[1]中国科学院地质研究所

出　　处：《岩石学报》1998年第2期163-175,共13页Acta Petrologica Sinica

基　　金：国家自然科学基金

摘　　要：中缅边界首次发现的麻粒岩相变质基性岩经历了两期变质作用的改造，依据共生矿物组合和矿物电子探针分析判定早期的变质作用的压力下限是０．８～１．０ＧＰａ，温度是７５０℃～８６０℃，为麻粒岩相变质作用；后期变质作用的温压是０．５９～０．８０ＧＰａ、６５０℃～７２０℃，为高角闪岩相变质作用。变质作用ＰＴ演化轨迹呈现降温减压的特点，指示俯冲作用和碰撞造山作用的大地构造背景。区域地质背景显示变质基性岩的早期变质作用与密支那古洋壳俯冲作用有关。构造分析得出后期的变质变形作用与研究区约２３．０８～０．６３Ｍａ前后的右行逆冲走滑剪切作用有关，是俯冲带上驮板片前缘强烈抬升的记录。那邦麻粒岩相变质岩的发现对滇西腾冲地块大地构造属性的研究、与密支那缝合带相关的板片俯冲、俯冲板片的裂离、俯冲带上驮板片前缘的抬升和变形研究具有重要意义。The recent discovery give geologists a good way to explore the tectonic frame of the western Yunnan and the subduction of the Myitkyina ocean crust,slabbreakoff,uplifting and deformation of overriding plate related to Myitkyina suture zone.The studied rocks experienced graunlitefacies metamorphism (>08￣10GPa,750℃￣860℃) and the upperamphibolitefacies metamorphism (059￣080GPa,640℃￣720℃)The early metamorphism is the result of the subduction of the Myitkyina ocean crust .The late metamorphism is attributed to the lateral strikeslip shearing deformation extensively occuring in the area about 2308±063Ma ago, It also records the uplifting process of the front part of the overriding plate.The metamorphic process shows a clockwise PT path suggesting that the tectonic setting is similar to the subducted zone or orogenic belt.

关 键 词：变质岩 变质基性岩 变质作用 构造意义 中缅边界 

分 类 号：P588.3[天文地球—岩石学] P548[天文地球—地质学]