Collaborative Research: Structure of the Crust and Upper Mantle Beneath the Tibetan Plateau Interior (INDEPTH III)

合作研究：青藏高原内部地壳和上地幔的结构（INDEPTH III）

• 批准号: 9614616
• 负责人: James Ni
• 金额: --
• 依托单位: New Mexico State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9614616&HistoricalAwards=false
• 关键词: Collaborative; Research; Structure; Crust; Upper

9614616 Ni This project is the third phase of Project INDEPTH (INternational DEep Profiling of Tibet and the Himalaya), a collaborateve, multinational, multidisciplinary program to investigate the lithosphere beneath the Himalaya/Tibet Plateau collision zone. Support is provided by NSF (Continental Dynamics Program), the Chinese National Natural Science Foundation, the Chinese Ministry of Geology and the DeutschesForschungs Gemneinshaft (Germany). Project INDEPTH has completed two field Programs in southern Tibet aimed at elucidating the structure of the lithosphere beneath this key region. The first, undertaken in 1992, was a feasibility study of deep reflection profiling on the high Tibetan Plateau that had the additional scientific goal of tracking the top of the Indian plate underthrusting the Himalaya (INDEPTH I). The second, undertaken in 1993-94, was a much more substantial program involving the acquisition of complementary CMP reflection, wide- angle reflection, broadband earthquake, magnetotelluric, and surface geological data along a transect (including INDEPTH I) extending approximately 300 km north of the crest of the Himalaya (INDEPTH II). The combined INDEPTH I-II results yeild a refined and exciting new view of the lithosphere beneath southern Tibet. They support some previous hypotheses while necessarily contradicting others. Among other things, the INDEPTH data imply that: 1)Indian continental crust does not extend as a coherent unit in the footwall of the India-Asia decollement for a significan distance north of the Tsangpo suture (and may not extend that far); 2) in contrast, Indian mantle lithosphere in contact with the overlying crust apparently does extend at least 150 km north of the suture; 3) the Tsangpo suture is not currently a lithosphere-penetrating structure, but rather is cut off in the mikkle crust by a younger feature, and finally, perhaps of greatest global significance; 4) the new data strongly imply the existence of a widespread mid- crustal partial melt layer beneath southern Tibet. Taken together the data lead to a model for the current behavior of the southern Tibetan Plateau lithosphere wherein the Indian continental crust underthrusting the southern margin of the Plateau partially melts in the vicinity of the North Himalayan domes, thereby contributing to a partially molten effectively fluid, mid-crustal layer that underlies the Plateau to the north. These results have important implications for how the Himalaya/Tibetan Plateau as a whole has evolved, and for our concepts of lithosphere formation and modification during continent-continent collisions in general. The purpose of INDEPTH III is to address three fundamental, interrelated issues about the nature and evolution of the lithosphere beneath the region. These are: 1) What is the magnitude and mechanism(s) of accommodation of Neogene/Quaternary deformation within the Tibetan Plateau? 2)Is there an areally extensive mid-crustal partial melt layer within the Tibetan crust that has exerted a primary control on the Neogene/Quaternary structural evolution and present morphology of the Plateau? and 3) What is the nature and cause of the reported first-order south to north change in the character of the mantle lithosphere beneath the Plateau? The program includes magnetotelluric profiling and broadband earthquake recording to assess the bulk electrical resistivity and velocity structure of the crust and upper mantle beneath the region. These data will provide primary information on the presence or absence of seismically attenuating crustal melt within the interior of the Plateau, and characterize the south-to- north upper mantle transition beneath the region. These efforts will be augmented by a modest controlled-source "test", and a modest field geology program aimed at delineating the geometry of upper crustal structure, the distribution of Neogene/Quaternary shortening, and the existence of a mid-crustal bright-s pot horizon which, if present, may indicate a mid-crustal partial melt zone. ***

9614616 ni该项目是Indepth项目的第三阶段（西藏和喜马拉雅山的国际深层概况），这是一个合作，跨国，跨学科的计划，旨在调查喜马拉雅/西藏高原碰撞区域下的岩石圈。 支持由NSF（Continental Dynamics计划），中国国家自然科学基金会，中国地质部和Deutschesforschungs Gemneinshaft（德国）提供支持。 Indepth项目已在西藏南部完成了两个野外计划，旨在阐明该关键区域下岩石圈的结构。 第一个于1992年进行的是对高藏高原的深思熟虑分析的可行性研究，该研究的进一步科学目标是跟踪印度板块的顶部，使喜马拉雅板（Indepth I）推动。 The second, undertaken in 1993-94, was a much more substantial program involving the acquisition of complementary CMP reflection, wide- angle reflection, broadband earthquake, magnetotelluric, and surface geological data along a transect (including INDEPTH I) extending approximately 300 km north of the crest of the Himalaya (INDEPTH II). I-II的组合结合结果是西藏南部下岩石圈的精致而令人兴奋的新观点。 他们支持一些以前的假设，同时必然与其他假设相矛盾。 除其他事项外，Indepth数据表明：1）印度大陆地壳在印度 - 亚洲 - 拆解的脚壁上没有作为连贯的单位扩展，因为在Tsangpo缝合线以北的显着距离（并且可能不会扩展到这么远）； 2）相反，印度地幔岩石圈与上覆的外壳接触，显然在缝合线以北至少延伸至少150公里。 3）tsangpo缝合线目前不是岩石圈的结构，而是通过年轻的特征在Mikkle Croust中切断，最后是最大的全球意义； 4）新数据强烈暗示着西藏南部下方的中壳部分融化层的存在。 总而言之，数据导致了一个模型，以实现藏族南部高原岩石圈的当前行为，其中印度大陆地壳在高原的南部边缘降低了北北喜马拉雅圆顶附近的部分融化，从而有效地有效地融化了一部分，有效地融化了北部的层，该层是北部的北部。 这些结果对整个喜马拉雅/藏高原的整体以及我们在大陆 - 大陆碰撞期间的岩石圈形成和修改的概念都具有重要意义。 Indepth III的目的是解决有关该地区下岩石圈的性质和演变的三个基本，相互关联的问题。 这些是：1）藏族高原内新近纪/第四纪变形的适应性的幅度和机制是什么？ 2）在藏族外壳内是否存在对新金属/第四纪结构性进化的主要控制和高原形态的主要控制？ 3）报告的高原下地幔岩石圈特征的一阶南向北变化的性质和原因是什么？ 该程序包括磁性分析和宽带地震记录，以评估该区域下地壳和上层地壳的大块电阻率和速度结构。 这些数据将提供有关高原内部内的地震层融化的存在或不存在的主要信息，并表征了该地区下面的北部上地幔过渡。 这些努力将通过适度的控制源“测试”以及旨在描述上层地壳结构的几何形状，新金元/四季缩短的分布以及存在中壳中的布莱特-S盆栽地平线的分布来增强这些努力。 ***