内蒙古大青山古元古代造山带中-下地壳深熔流变研究  

Rheology of the anatectic mid-lower crust in the Paleoproterozoic orogenic belt in Daqingshan, Inner Mongolia

作　　者：刘同君 李伟民[1,2] 刘永江 金巍 邵弋伦[5] LIU TongJun;LI WeiMin;LIU YongJiang;JIN Wei;SHAO YiLun(College of Earth Sciences,Jilin University,Changchun 130061,China;Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun 130026,China;Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,MOE,College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266100,China;Department of Geology,University of Otago,Dunedin 9054,New Zealand)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]自然资源部东北亚矿产资源评价重点实验室,长春130026 [3]深海圈层与地球系统前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,青岛266100 [4]青岛海洋科学与技术国家实验室,海洋矿产资源评价与探测技术功能实验室,青岛266100 [5]奥塔哥大学地质系,达尼丁9054

出　　处：《岩石学报》2020年第11期3309-3330,共22页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41772212、41872215);泰山学者计划(ts20190918);青岛市创新领军人才计划(19-3-2-19-zhc);筑峰人才工程联合资助。

摘　　要：内蒙古大青山地区是典型的早前寒武纪造山带根部岩石出露区,大量下地壳高级变质-深熔岩石中保留了丰富的流变构造样式,是开展部分熔融岩石流变行为研究的天然实验室。本文对内蒙古大青山地区雪海沟和大庙-忽鸡沟构造带内变形岩石开展了宏观、微观构造解析、EBSD组构以及锆石U-Pb年代学研究,并结合前人研究成果,考查了不同构造层次、不同熔融程度岩石的流变特征及其与造山过程的耦合关系。研究结果表明,雪海沟至大庙-忽鸡沟地区体现了造山带地壳结构层次由深至浅的特点。深部构造层次(雪海沟)高级深熔条件下,宏观上以各种形式的浅色脉体参与岩石流变,深熔熔体夹矿物颗粒流形成网状的断续条带状构造。微观上斜长石受扩散蠕变、颗粒边界滑移和颗粒流动影响,一般没有明显的晶内变形组构,CPO(晶格优选方位)发育不明显。在中深部构造层次(大庙-忽鸡沟)深熔作用相对较弱,宏观上形成平行片麻理的较规则条纹/条带构造。微观上斜长石发生位错蠕变,CPO发育明显。此外,角闪石在不同构造层次下均表现出位错蠕变特征,结晶优选方向受深熔作用影响不大。上述变形样式和机制,体现了造山带根部高级变质-深熔岩石在固-液两相介质中,发生水平层状粘-塑性流动变形特点。随后深熔岩石的塑性流动变形伴随加厚地壳的伸展减薄-隆升过程而逐渐硬化并遭受剥露。The Daqingshan area in Inner Mongolia is a typical area of Early Paleoproterozoic orogenic belt in the North China Craton,in where a large number of high grade metamorphic-anatectic rocks are widely exposed,and it preserved abundant rheological structural patterns formed in the deeper level of continental crust. It therefore becomes a natural laboratory for the study of rheological behavior and mechanism of partially molten rock. This study carried out detail macroscopic-microscopic deformation,EBSD fabric analysis and zircon U-Pb chronology on the high-grade metamorphic-anatectic rocks from the Xuehaigou and Hujigou-Damiao belts in the Daqingshan area,and combining with the previous research data,we focus on the rock rheology with partial melting and its influence on the orogenic process. The results presented here suggest that the deformation patterns occurred in the deeper crustal level in the Xuehaigou belt and in the middle-deep level in the Damiao-Hujiigou belt in Daqingshan Paleoproterozoic orogenic belt. Under advanced metamorphic-anatectic conditions at the deep crustal level( e. g. Xuehaigou area),macroscopically,various forms of lightcolored veins( melt) are involved in rheological deformation,usually showing a intermittent network-like zone formed by melt flow entraining mineral particles. Microscopically,single minerals,especially feldspars,are affected by diffusion creep,grain boundary slip and particle flow,instead of obvious deformation fabric. Therefore,there is no or very weak Crystallographic Preferred Orientation( CPO) development for the grains. In contrast,under relatively weak metamorphic-anatectic conditions in the middle-deep crustal level( e. g. Damiao-Hujiigou area),the melt content is relatively lower due to the weak anatexis,and some stripe or banded structures are formed macroscopically. Microscopically,minerals( e. g. plagioclase) usually suffer dislocation creep deformation and develop strong CPO. Significantly,the amphibole shows obvious dislocation creep characteristics at both i

关 键 词：古元古代造山带 构造片麻岩 部分熔融 构造层次 岩石流变 变形机制 组构分析 

分 类 号：P542[天文地球—构造地质学] P588.2[天文地球—地质学]