喜马拉雅汇聚带结构-属性解剖及印度-欧亚大陆最终拼贴格局
发布时间：2018-08-31 08:53
【摘要】：针对印度与欧亚大陆的碰撞方式与时限存在争议的现状,为探讨学术界关于喜马拉雅造山作用观点分歧的原因,本文首先综述了汇聚带结构-属性解剖方法论与基本原则,指出大陆碰撞造山带实际上包括了多种类型,但常见的大陆碰撞造山带往往包括了被动大陆边缘和活动大陆边缘的诸多块体拼贴的格局,其最终的碰撞格局及缝合带产出位置由增生楔底部界面控制,可能在拼贴后呈起伏状或者Z字形等复杂产状.厘定最终碰撞缝合带的可行思路,就是解剖活动大陆边缘结构,确定其作为俯冲上盘的岩石类型属性,特别是增生楔、高压-超高压和巴洛(Barrovian)变质带以及上叠弧前盆地.同时,找寻被动大陆边缘与活动大陆边缘接触的最外、最远边界及其趋近界面,就能厘定缝合面在地表的出露线.根据地球物理资料和高压变质岩等产出位置,限定其深部的产出状态,就可以限定缝合带的产出状态.结合汇聚带结构-属性解剖方法论与基本原则讨论,本文指出喜马拉雅南部汇聚带成分、结构复杂,急需重新开展结构-属性解剖.在综合前人研究资料的基础上,结合我们自己的最新研究结果,进一步总结探讨喜马拉雅造山带结构-属性的新认识,其中雅江蛇绿岩带包含多种构造组分,并非代表单一缝合带,可能是位于弧前后盾(backstop)的多地质单元组合.特提斯喜马拉雅(THS)包含混杂岩结构组成,具有"基质+块体"的结构特征;统一的南向古水流物源、单一的欧亚大陆特征碎屑锆石年龄谱,均表明特提斯喜马拉雅(THS)应该是冈底斯弧前体系,在最终碰撞前具有欧亚大陆属性.高喜马拉雅(GHS)和低喜马拉雅(LHS)组成复杂,由俯冲碰撞作用产生的榴辉岩等高压变质岩就位于高喜马拉雅(GHS)和低喜马拉雅(LHS)的顶部.根据造山带内的高压变质岩石折返都就位于俯冲上盘的产出特征,高喜马拉雅(GHS)和低喜马拉雅(LHS)的顶部含高压变质岩部分应属于俯冲上盘单元,俯冲带必须位于其下(南)部.因此,印度大陆最主要也是最终的俯冲作用是沿该俯冲带结构面发生.低喜马拉雅(LHS)和锡瓦里克的岩石组合表明其主体不发育混杂带,很可能属于印度的前陆体系.通过对喜马拉雅造山带内不同单元的结构-属性解剖,结合俯冲拼贴相关的构造变形年龄,本文认为印度与欧亚大陆最终的碰撞拼贴发生在14Ma之后.青藏地区南北向裂谷的发育、藏东地区哀牢山等剪切带左行-右行的转换等构造事件的发生,均可以协调地反映在俯冲带的影响范围和动力学控制之中.通过对喜马拉雅造山带的研究,提出喜马拉雅造山带最终碰撞拼贴新模式,表明造山带的结构-属性解剖是正确认识造山带的关键,其分析方法可以应用到全球造山带的研究.同时,本文也提出一些关于喜马拉雅造山带结构-属性研究未来需要关注的重要科学问题.
[Abstract]:In view of the current situation that the collision mode and time limit between India and Eurasia are controversial, in order to explore the reasons for the different views on Himalayan orogeny in academic circles, this paper first summarizes the methodology and basic principles of structure-attribute anatomy of convergent zone. It is pointed out that the continental collision orogenic belt actually includes many types, but the common continental collision orogenic belt often includes many blocks of passive continental margin and active continental margin. The final collision pattern and the location of the suture belt are controlled by the interface at the bottom of the accretive wedge, which may take on a complex occurrence such as undulation or Z shape after collage. The feasible way to determine the final collision suture zone is to dissect the active continental margin structure and determine its rock type attributes as the subduction upper disc, especially the accretive wedge, the high-pressure ultra-high pressure and Barlow (Barrovian) metamorphic belt, as well as the prearc basin. At the same time, finding the outermost, farthest boundary and its approaching interface between passive continental margin and active continental margin can determine the outcrop line of suture surface on the surface. According to the geophysical data and the high pressure metamorphic rocks, the occurrence state of the suture zone can be defined. Based on the discussion of the methodology and basic principles of structure-attribute anatomy of convergent zone, this paper points out that the composition of convergent zone in southern Himalayas is complex, and it is urgent to develop structure-attribute anatomy again. On the basis of synthesizing the previous research data and combining with our own latest research results, we further summarize and discuss the new understanding of structure-attribute of Himalayan orogenic belt, in which the Yajiang ophiolite belt contains a variety of tectonic components. It does not represent a single suture zone, but may be a combination of multiple geological units located in front and rear shield (backstop). The Tethys Himalayan (THS) contains a melange structure with a "matrix block" structure, a unified southward paleocurrent source, a single Eurasian characteristic zircon age spectrum, It is suggested that the Tethys Himalayan (THS) should be a Gangdis prearc system with Eurasian attributes before the final collision. The composition of high Himalayan (GHS) and low Himalayan (LHS) is complex, and the high pressure metamorphic rocks, such as eclogite, which are produced by subduction and collision, are located at the top of high Himalayan (GHS) and low Himalayan (LHS). According to the exhumation characteristics of high-pressure metamorphic rocks in the orogenic belt, the high-pressure metamorphic rocks at the top of the high Himalayan (GHS) and the low Himalayan (LHS) should belong to the subduction upper plate unit, and the subduction zone must be located in the lower (south) part. Therefore, the main and final subduction in the Indian continent is along the structural plane of the subduction zone. The rock assemblages of low Himalayan (LHS) and SiVarik indicate that their main body is not developed and probably belongs to the Foreland system of India. Based on the structure-attribute anatomy of different units in the Himalayan orogenic belt and the tectonic deformation age associated with subduction collage, it is considered that the final collision collage between India and Eurasia occurred after 14Ma. The development of the north-south rift in the Qinghai-Tibet region and the tectonic events such as the left-to-right transition of the Ailaoshan shear belt in the eastern Tibetan region can be reflected harmoniously in the influence range and dynamic control of the subduction zone. Based on the study of Himalayan orogenic belts, a new model of final collision collage of Himalayan orogenic belts is proposed, which indicates that the structure-attribute anatomy of orogenic belts is the key to correct understanding of orogenic belts, and its analytical method can be applied to the study of global orogenic belts. At the same time, this paper also puts forward some important scientific problems about the structure-attribute of Himalayan orogenic belt.
【作者单位】： 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室;中国科学院青藏高原地球科学卓越创新中心;中国科学院大学地球科学学院;
【基金】：中国科学院战略性先导科技专项项目(B类)(编号:XDB03010801,XDB18020203) 国家自然科学基金项目(批准号:41230207,41190075,41472192) 国际地球科学计划IGCP-592项目资助
【分类号】：P542
本文编号：2214503
[Abstract]:In view of the current situation that the collision mode and time limit between India and Eurasia are controversial, in order to explore the reasons for the different views on Himalayan orogeny in academic circles, this paper first summarizes the methodology and basic principles of structure-attribute anatomy of convergent zone. It is pointed out that the continental collision orogenic belt actually includes many types, but the common continental collision orogenic belt often includes many blocks of passive continental margin and active continental margin. The final collision pattern and the location of the suture belt are controlled by the interface at the bottom of the accretive wedge, which may take on a complex occurrence such as undulation or Z shape after collage. The feasible way to determine the final collision suture zone is to dissect the active continental margin structure and determine its rock type attributes as the subduction upper disc, especially the accretive wedge, the high-pressure ultra-high pressure and Barlow (Barrovian) metamorphic belt, as well as the prearc basin. At the same time, finding the outermost, farthest boundary and its approaching interface between passive continental margin and active continental margin can determine the outcrop line of suture surface on the surface. According to the geophysical data and the high pressure metamorphic rocks, the occurrence state of the suture zone can be defined. Based on the discussion of the methodology and basic principles of structure-attribute anatomy of convergent zone, this paper points out that the composition of convergent zone in southern Himalayas is complex, and it is urgent to develop structure-attribute anatomy again. On the basis of synthesizing the previous research data and combining with our own latest research results, we further summarize and discuss the new understanding of structure-attribute of Himalayan orogenic belt, in which the Yajiang ophiolite belt contains a variety of tectonic components. It does not represent a single suture zone, but may be a combination of multiple geological units located in front and rear shield (backstop). The Tethys Himalayan (THS) contains a melange structure with a "matrix block" structure, a unified southward paleocurrent source, a single Eurasian characteristic zircon age spectrum, It is suggested that the Tethys Himalayan (THS) should be a Gangdis prearc system with Eurasian attributes before the final collision. The composition of high Himalayan (GHS) and low Himalayan (LHS) is complex, and the high pressure metamorphic rocks, such as eclogite, which are produced by subduction and collision, are located at the top of high Himalayan (GHS) and low Himalayan (LHS). According to the exhumation characteristics of high-pressure metamorphic rocks in the orogenic belt, the high-pressure metamorphic rocks at the top of the high Himalayan (GHS) and the low Himalayan (LHS) should belong to the subduction upper plate unit, and the subduction zone must be located in the lower (south) part. Therefore, the main and final subduction in the Indian continent is along the structural plane of the subduction zone. The rock assemblages of low Himalayan (LHS) and SiVarik indicate that their main body is not developed and probably belongs to the Foreland system of India. Based on the structure-attribute anatomy of different units in the Himalayan orogenic belt and the tectonic deformation age associated with subduction collage, it is considered that the final collision collage between India and Eurasia occurred after 14Ma. The development of the north-south rift in the Qinghai-Tibet region and the tectonic events such as the left-to-right transition of the Ailaoshan shear belt in the eastern Tibetan region can be reflected harmoniously in the influence range and dynamic control of the subduction zone. Based on the study of Himalayan orogenic belts, a new model of final collision collage of Himalayan orogenic belts is proposed, which indicates that the structure-attribute anatomy of orogenic belts is the key to correct understanding of orogenic belts, and its analytical method can be applied to the study of global orogenic belts. At the same time, this paper also puts forward some important scientific problems about the structure-attribute of Himalayan orogenic belt.
【作者单位】： 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室;中国科学院青藏高原地球科学卓越创新中心;中国科学院大学地球科学学院;
【基金】：中国科学院战略性先导科技专项项目(B类)(编号:XDB03010801,XDB18020203) 国家自然科学基金项目(批准号:41230207,41190075,41472192) 国际地球科学计划IGCP-592项目资助
【分类号】：P542
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