东天山三条高压变质带地质特征和流体作用  

The geologic characteristics and fluid evolution in the three high-pressure metamorphic belts of eastern Tianshan.

作　　者：刘斌[1] 钱一雄[2] 

机构地区：[1]同济大学地下工程系,上海200092 [2]中国石化勘探开发研究院无锡实验地质研究所,无锡214151

出　　处：《岩石学报》2003年第2期283-296,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金(40173029;49672161);八五国家重点科技攻关项目(85-101-02-01)部分研究成果

摘　　要：微板块活动边缘常常产生高压变质作用,我们在东天山地区发现了三条高压变质带,分别出露在南天山北缘、中天山北缘和北天山南缘的早古生代至晚古生代地层中,它们是天山微板块多期次俯冲-碰撞-拼贴作用的产物。(南天山北缘铜花山高压变质带中有不同变异的蓝闪石类高压矿物,蓝闪石Ar^(40)/Ar^(39)同位素测定为360Ma年龄,而在同一带的西部的榆树沟有C型和B型的榴辉岩分布。中天山北缘乌斯特沟-米什沟高压变质带中发现了青铝闪石,同一阶段生成的多硅白云母为345Ma的年龄;北天山南缘后峡高压变质带中以出露在石炭世地层中钠闪石和多硅白云母为特征,三条高压变质带均经历过三个变质-变形作用阶段:①高压变质;②退变质;③韧性-脆性变质变形作用。) 流体活动与微板块构造作用密切相关,不同构造阶段有不同的变质-变形作用和矿物-流体反应:①高压变质作用阶段:微板块碰撞阶段产生不同的进变质作用,主要发生脱挥发组分的矿物反应,含水矿物转化成无水或少水矿物。南天山北缘有两次微板块与洋壳碰撞-俯冲作用,第一次碰撞-俯冲的热力学条件是:中-高温、高压和埋藏深度较大(540～720℃,0.92～1.29GPa,35～>50km),导致榴辉岩的生成,除了大量挥发组分逸出以外,另有不少熔体产生。It is well known that the active margin of micro-plates is usually associated with the high-pressure metamorphism. The three high-pressure metamorphic belts had been identified, which had been respectively exposed in the Palaeozoic stratigraphic succession in the north margin of Southern Tianshan and the Middle Tianshan, as well as in the south margin of Northern Tianshan, and had been supposed as the results of multi-periods subduction, collision and collage of micropalaeoslabs. The studies demonstrated that the high-pressure minerals, such as glaucophane with varied chemical composition and the (ArP)-Ar-40/(39) Ar 360Ma isotopic spectrum age are distributed in the high-pressure metamorphic belt in north margin of Southern Tianshan and ecologits are discerned along Yushugou, which lies to the west of the same belt, and crossites are confirmed in Wusitegou - Mishigou high-pressure metamorphic belt of the northern margin of the Middle Tianshan, and coeval phengite have the 345Ma age, while outcropping riebeckites and phenggites in stratum of Caboniferous System are developed in Houxia high-pressure metamorphic belts in the southern margin of Northern Tianshan. furthermore, the above three high-pressure belts had undergone the three-stage of deformation and metamorphic transformation, i.e. (1) the high pressure metamorphism; (2) the retreated metamorphism; (3)the ductile-brittle metamorphism and deformation. A wealth of evidence indicates that the fluid activities has close relationship with the tectonic movement of micro-palaeoslabs, and the different metamorphism and deformation and its related fluid-mineral reactions are genetically distinct, i.e. during the high pressure metamorphic transformation, the varied degree of progressive metamorphism is of characteristic of collisional of micropalaeoslabs, and the devolatilization in the fluid-mineral reactions are frequently occurred, and this render the hydrates into either the non-hydrates or less-hydrated molecule minerals. The studies also shows that there are tw

关 键 词：东天山高压变质带 三个变质-变形作用阶段 流体-岩石相互作用 构造演化 

分 类 号：P542.4[天文地球—构造地质学]