南阿尔金断裂的韧性剪切作用时代及其构造意义  

Ductile shearing age of the south Altun fault and its tectonic implications

作　　者：崔军文[1] 

机构地区：[1]大陆构造与动力学国家重点实验室,中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2011年第11期3422-3434,共13页Acta Petrologica Sinica

基　　金：国家自然科学基金创新群体项目(40921001);国土资源部行业基金项目(201011034);中国地质调查局基础研究项目(1212010610105、1212011121275);中国石化股份有限公司科技开发部项目(YPH08110)联合资助

摘　　要：位于阿尔金山腹地古元古界阿尔金群深变质岩系与中-新元古界浅变质岩系间的南阿尔金断裂,是1条以近于E-W走向,微向S高角度倾斜的大型逆冲断裂,它经历了韧性变形和脆性变形2个构造演化阶段。韧性剪切带的形成始于晚寒武世,强烈活动期为中奥陶世-志留纪(468.4～412.2Ma),早-中泥盆世、早石炭世、晚二叠世和早侏罗世时期,剪切带进入以高、中温为主的韧性变形期,随着时间推移,变形温度不断降低,剪切作用的强度明显减弱,早侏罗世后,南阿尔金断裂完全进入以脆性变形为主的构造演化阶段。南阿尔金断裂以北广泛分布的年龄区间为491.3±4.6～413.8±8.0Ma的钙碱性系列花岗岩和断裂南侧出露的时代为519±37～500±10Ma的榴辉岩和角闪糜棱岩,表明在发生极性向北的逆冲型韧性剪切作用前,沿南阿尔金断裂曾发生过自南而北的岩石圈尺度的俯冲作用。因此,南阿尔金断裂是阿尔金山腹地的1条重要的早古生代板块汇聚、碰撞带。The South Altun fault,lying between the Neoarchean-Paleoproterozoic high-grade metamorphic rocks of the Altun Group and the Meso-Neoproterozoic low-grade metamorphic rocks in the Altun hinterland,is a roughly E-W-trending and slightly S-dipping high-angle large thrust fault.It has undergone two tectonic evolution stages,i.e.ductile deformation and fragile deformation.The ductile shear zone took shape in the Late Cambian,and shearing was intensive during the Middle Ordovician-Silurian（468.4～412.2Ma）.In Early-Middle Devonian,Early Carboniferous,Late Permian and Early Jurassic periods,the shear zone entered the ductile deformation stage dominated by high and medium temperatures.With the elapse of time,the deformation temperature continued to decrease,and shearing was obviously weakened.After the Early Jurassic,the fault completely entered the tectonic evolution stage dominated by fragile deformation.However,it is indicated by the 491.3±4.6～413.8±8.0Ma calc-alkaline granites widely distributed north of the fault and the 500±10～519±37Ma eclogite and amphibole-mylonite exposed on the south side of the fault that there had been a lithosphere-scale subduction from south to north along the fault before a thrust-type ductile shearing of north polarity occurred.Therefore,this fault is an important convergance and collision zone of Early Paleozoic plates in the Altun hinterland.

关 键 词：南阿尔金断裂 韧性剪切 40Ar/39Ar同位素年代学 中奥陶-志留纪 动力学 

分 类 号：P588.34[天文地球—岩石学]