喜馬拉雅匯聚帶結構-屬性解剖及印度-歐亞大陸最終拼貼格局
發(fā)布時間：2018-08-31 08:53
【摘要】：針對印度與歐亞大陸的碰撞方式與時限存在爭議的現(xiàn)狀,為探討學術界關于喜馬拉雅造山作用觀點分歧的原因,本文首先綜述了匯聚帶結構-屬性解剖方法論與基本原則,指出大陸碰撞造山帶實際上包括了多種類型,但常見的大陸碰撞造山帶往往包括了被動大陸邊緣和活動大陸邊緣的諸多塊體拼貼的格局,其最終的碰撞格局及縫合帶產(chǎn)出位置由增生楔底部界面控制,可能在拼貼后呈起伏狀或者Z字形等復雜產(chǎn)狀.厘定最終碰撞縫合帶的可行思路,就是解剖活動大陸邊緣結構,確定其作為俯沖上盤的巖石類型屬性,特別是增生楔、高壓-超高壓和巴洛(Barrovian)變質(zhì)帶以及上疊弧前盆地.同時,找尋被動大陸邊緣與活動大陸邊緣接觸的最外、最遠邊界及其趨近界面,就能厘定縫合面在地表的出露線.根據(jù)地球物理資料和高壓變質(zhì)巖等產(chǎn)出位置,限定其深部的產(chǎn)出狀態(tài),就可以限定縫合帶的產(chǎn)出狀態(tài).結合匯聚帶結構-屬性解剖方法論與基本原則討論,本文指出喜馬拉雅南部匯聚帶成分、結構復雜,急需重新開展結構-屬性解剖.在綜合前人研究資料的基礎上,結合我們自己的最新研究結果,進一步總結探討喜馬拉雅造山帶結構-屬性的新認識,其中雅江蛇綠巖帶包含多種構造組分,并非代表單一縫合帶,可能是位于弧前后盾(backstop)的多地質(zhì)單元組合.特提斯喜馬拉雅(THS)包含混雜巖結構組成,具有"基質(zhì)+塊體"的結構特征;統(tǒng)一的南向古水流物源、單一的歐亞大陸特征碎屑鋯石年齡譜,均表明特提斯喜馬拉雅(THS)應該是岡底斯弧前體系,在最終碰撞前具有歐亞大陸屬性.高喜馬拉雅(GHS)和低喜馬拉雅(LHS)組成復雜,由俯沖碰撞作用產(chǎn)生的榴輝巖等高壓變質(zhì)巖就位于高喜馬拉雅(GHS)和低喜馬拉雅(LHS)的頂部.根據(jù)造山帶內(nèi)的高壓變質(zhì)巖石折返都就位于俯沖上盤的產(chǎn)出特征,高喜馬拉雅(GHS)和低喜馬拉雅(LHS)的頂部含高壓變質(zhì)巖部分應屬于俯沖上盤單元,俯沖帶必須位于其下(南)部.因此,印度大陸最主要也是最終的俯沖作用是沿該俯沖帶結構面發(fā)生.低喜馬拉雅(LHS)和錫瓦里克的巖石組合表明其主體不發(fā)育混雜帶,很可能屬于印度的前陸體系.通過對喜馬拉雅造山帶內(nèi)不同單元的結構-屬性解剖,結合俯沖拼貼相關的構造變形年齡,本文認為印度與歐亞大陸最終的碰撞拼貼發(fā)生在14Ma之后.青藏地區(qū)南北向裂谷的發(fā)育、藏東地區(qū)哀牢山等剪切帶左行-右行的轉換等構造事件的發(fā)生,均可以協(xié)調(diào)地反映在俯沖帶的影響范圍和動力學控制之中.通過對喜馬拉雅造山帶的研究,提出喜馬拉雅造山帶最終碰撞拼貼新模式,表明造山帶的結構-屬性解剖是正確認識造山帶的關鍵,其分析方法可以應用到全球造山帶的研究.同時,本文也提出一些關于喜馬拉雅造山帶結構-屬性研究未來需要關注的重要科學問題.
[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.
【作者單位】： 中國科學院地質(zhì)與地球物理研究所巖石圈演化國家重點實驗室;中國科學院青藏高原地球科學卓越創(chuàng)新中心;中國科學院大學地球科學學院;
【基金】：中國科學院戰(zhàn)略性先導科技專項項目(B類)(編號:XDB03010801,XDB18020203) 國家自然科學基金項目(批準號:41230207,41190075,41472192) 國際地球科學計劃IGCP-592項目資助
【分類號】：P542
本文編號：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.
【作者單位】： 中國科學院地質(zhì)與地球物理研究所巖石圈演化國家重點實驗室;中國科學院青藏高原地球科學卓越創(chuàng)新中心;中國科學院大學地球科學學院;
【基金】：中國科學院戰(zhàn)略性先導科技專項項目(B類)(編號:XDB03010801,XDB18020203) 國家自然科學基金項目(批準號:41230207,41190075,41472192) 國際地球科學計劃IGCP-592項目資助
【分類號】：P542
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