阿尔金南缘早古生代岩浆作用及碰撞造山过程  

Early Paleozoic Magmatism and Collision Orogenic Process of the South Altyn

作　　者：康磊[1] 校培喜[1] 高晓峰[1] 奚仁刚[1] 杨再朝[1] 

机构地区：[1]国土资源部岩浆作用成矿与找矿重点实验室,中国地质调查局西安地质调查中心,西安710054

出　　处：《地质学报》2016年第10期2527-2550,共24页Acta Geologica Sinica

基　　金：中国地质调查局国土资源大调查研究项目(12120113044500);国家自然科学基金项目(41202044,41272089,41002063);陕西省自然科学基金项目(2012JM5004)资助的成果

摘　　要：阿尔金南缘发育着大规模多种多样的早古生代岩浆岩,对不同阶段岩浆作用时限、源岩特征及其形成机制的系统研究,对全面理解该地区早古生代洋-陆转换、大陆深俯冲、板片断离等地球动力学过程具有重要的科学意义。本文通过对早古生代岩浆岩的时空分布、岩石类型、同位素定年数据和岩石地球化学资料的综合分析,研究岩浆活动期次和岩石成因机制,结合区域资料,将阿尔金南缘早古生代构造-岩浆演化过程分为4个阶段：1〉500Ma,由E-MORB、N-MORB型基性—超基性岩浆岩和O型埃达克岩组成,为＂南阿尔金洋盆＂洋脊扩张和板片俯冲消减作用阶段;2497~472Ma,由I型和S型花岗岩组成,具C型埃达克岩特征,是上地壳砂质岩和下地壳玄武质岩石高压部分熔融的产物,属于碰撞造山的陆壳深俯冲阶段;3469~445Ma,由OIB型碱性基性-超基性岩和I型-S型花岗岩组成,具板片断离后同折返岩浆岩特征,前者形成与陆内伸展裂解环境,后者以低Sr（或高Sr）、高Y和低Sr/Y为主（少量高Sr、低Y）,是上地壳折返减压部分熔融（局部仍为挤压作用）的产物,属于初始后碰撞伸展的地壳折返阶段;4424~385Ma,由具低Sr、高Y特征的A型岩浆岩组成,是上地壳砂质-泥质岩高温低压部分熔融的产物,为后碰撞伸展拉张阶段。根据岩浆活动特征和构造演化过程,提出了阿尔金南缘早古生代构造-岩浆演化模式图。The spatial and temporal distribution,sources and petrogenesis of the massive diverse early Paleozoic magmatite in the South Altyn Tagh,are helpful to comprehensive understanding the geodynamic processes of ocean-land transition,continental deep subduction,continantal slab break-off during the collisional orogeny.In this paper,we come to the conclusion that tectonic magmatic evolution of the early Paleozoic south Altyn Tagh should be divided into four stages according to the rock types,ages and geochemistry of these magmatic associations：（1）〉500Ma,the stage of ocean ridge spreading and slab subduction,the magmatic rocks are characterized by E-MORB、N-MORB and O-type adakites;（2）497~472Ma,the stage of deep subduction of continental crust during continental collision,the magmatic rocks that consist of I and S-types,and C-type adakites,were products of the high press partial melting of arenaceous rocks in upper crust or basalt in lower crust;（3）469~445Ma,the stage of primary post-collision setting,basicultrabasic rock being characterized by OIB and I-S types granites are composed of bimodal magmatite relating continantal slab uplifting,the former formed within intracontinental rift environment,the latter with low/high Sr and low Sr/Y ratios（high Sr and low Y,few）,originated from partial melting of upper cruslt in the condition of reducing stress;（4）424~385Ma,the stage of post-collision setting,A-type magmatite with high Y and low Sr should be the productions of mudstones and sandstones partial melting in upper crust at high temperature and low pressure.According to magmatic activity and tectonic evolution,the early Paleozoic tectonic evolution models of South Altyn Tagh are proposed.

关 键 词：阿尔金南缘 早古生代 岩浆岩 岩浆—构造演化过程 

分 类 号：P542[天文地球—构造地质学]