Collaborative Research: Investigation of a Proposed Suture Between East and West Gondwana - - An Integrated Field, Geochronologic, and Remote-Sensing Analysis In East Madagascar

该项目将调查马达加斯加东部一条地质缝合线（Betsimisaraka缝合线）的年龄、结构几何形状和区域范围，该缝合线宽约50公里，长700多公里，将东、西冈瓦纳大陆碎片焊接在一起。缝合假说对目前关于罗迪尼亚地貌及其向冈瓦纳的转变的范式提出了根本性的挑战。本研究的目的是确定东武带关键部位的陆块增生和末端缝合事件的构造收敛、运动学和时间，这些事件在全球范围内对新元古代构造具有重要意义。研究将通过地质测绘和结构分析的综合计划，以及遥感分析（Landsat TM和SIR C/X雷达）、U-Pb地质年代学、地球化学和放射性成因同位素（Re-Os, Sm-Nd）调查进行。结构调查和样本收集将沿着五条河流横断面进行，这些河流横断面穿过拟议的缝合线。在建议的缝合线内，有几米和几公里大小的橄榄岩、哈尔兹布尔岩、辉长岩和玄武岩块，被解释为前莫桑比克大洋的遗迹。地球化学和地质年代学分析将限制它们的年龄和起源，并为缝合假说提供重要的检验。构造调查和对拟议缝合线内部和附近岩石的U-Pb定年将使我们能够评估该假设的其他关键因素，并对冈瓦纳大陆地体的配置提出重要的限制。TM成像和SIR C/X雷达分析将揭示宏观尺度的运动学关系，并为更大尺度的缝合线外推提供依据。这项工作将导致对EAO东部关键部分的运动学，年龄和整体结构收敛的新理解，在那里对其演变的强烈分歧观点正在出现。这项研究将涉及马达加斯加和美国的专业同事之间的合作，并允许美国和马达加斯加的学生参与和培训实地和实验室研究。

This project will investigate the age, structural geometry, and regional extent of a proposed geological suture (the Betsimisaraka suture) in East Madagascar, approximately 50 km wide and over 700 km long, that welds the continental fragments of East and West Gondwana. The suture hypothesis poses a fundamental challenge to the current paradigm regarding the configuration of Rodinia and its transformation to Gondwana. The objectives of this research are to determine the structural vergence, kinematics, and timing of terrane-accretion and terminal-suturing events in the critical part of the EAO that have important global-scale implications for Neoproterozoic tectonics. Research will proceed through an integrated program of geologic mapping and structural analysis, together with remote sensing analysis (Landsat TM and SIR C/X radar), U-Pb geochronology, geochemical, and radiogenic isotope (Re-Os, Sm-Nd) investigations. The structural investigations and sample collections will be made along five river transects that traverse the proposed suture. Within the proposed suture are meter-and km-scale blocks of peridotite, hartzburgite, gabbro, and basalt interpreted as relicts of the former Mozambique Ocean. Geochemical and geochronological analysis of these will place constraints on their age and origin, and provide an important test of the suture hypothesis. Structural investigations and U-Pb dating of rocks within and adjacent to the proposed suture will allow us to evaluate other critical elements of the hypothesis, and place important constraints on the configuration of continental terranes within Gondwana. TM imaging and SIR C/X radar analysis will reveal macro-scale kinematic relations and provide a basis for extrapolation of the suture to a larger scale. This work will lead to a new understanding of kinematics, age and overall structural vergence in the critical, eastern part of the EAO where strongly divergent views of its evolution are emerging. The research will involve collaboration between professional colleagues in Madagascar and the U.S., and allow for the participation and training of American and Malagasy students in field- and laboratory-based research.