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拟议的一条地质缝合线(Betsimisaraka缝合线)的年龄、构造几何和区域范围，该缝合线宽约50公里，长700多公里，将冈瓦那东部和西部的大陆碎片焊接在一起。缝合假说对目前关于罗迪尼亚的构型及其向冈瓦那的转变的范式提出了根本的挑战。这项研究的目的是确定对新元古代构造具有重要全球意义的Eao关键部分的地体吸积和末端缝合事件的构造汇聚、运动学和时间。研究将通过地质填图和构造分析以及遥感分析(Landsat TM和SIR C/X雷达)、铀-铅地质年代学、地球化学和放射性同位素(Re-Os，Sm-ND)调查的综合方案进行。结构调查和样品采集将沿着横跨拟议缝合线的五个河流横断面进行。在拟议的缝合线内是米和公里级的橄榄岩、方辉橄榄岩、辉长岩和玄武岩区块，被解释为前莫桑比克大洋的遗迹。对它们的地球化学和地质年代学分析将限制它们的年龄和来源，并为缝合假说提供重要的检验。对拟议缝合线内和邻近岩石的构造调查和U-Pb测年将使我们能够评估该假说的其他关键元素，并对冈瓦那大陆地体的配置施加重要限制。TM成像和SIR C/X雷达分析将揭示大尺度的运动学关系，并为更大范围的缝合外推提供依据。这项工作将导致对EAO关键东部的运动学、年龄和总体结构趋同的新理解，在那里出现了对其演化的强烈分歧的观点。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基于实地和实验室的研究。

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.