Distributed Extension at the Galapagos Triple Junction, Eastern Equatorial Pacific

OCE-0751831智力价值：这项工作的总体目标是了解构造板块三交界处的变形是如何分布的，特别是阐明加拉帕戈斯三交界处的运动学演化。研究计划包括在加拉帕戈斯三重结合部进行为期5天的多波束水深测量和同步磁强计测量，这是一个海脊-海脊-海脊(RRR)三重结合处，科科斯、纳斯卡和太平洋板块在这里相交，由加拉帕戈斯微板块隔开。具体目标是：1)确定与传播的科科斯-纳斯卡(C-N)裂谷有关的应力是否控制着岩石圈向北和向南裂谷的位置和稳定性，2)了解什么条件可能导致Dietz深裂谷南部RRR三重结点的稳定以及随后加拉帕戈斯旋转微板块的发展。第二个目标是对加拉帕戈斯微盘的旋转速度施加额外的限制，这仍然是一个有争议的问题。在C-N裂谷以北，有一系列的瞬变裂谷和与EPR的三重交汇处。一个简单的裂隙相互作用模型预测，这些北部裂谷的位置受C-N裂谷尖端到EPR的距离控制。该模型还预测，拉应力应该是关于裂谷对称的，因此，瞬时裂谷可能发生在C-N裂谷以南。目前，情况并非如此：在加拉帕戈斯南部，微板块已经稳定了1年。然而，在微板块形成之前，没有收集到沿南部三重结迹的数据，以评估当时是否存在对称的多个跳跃裂谷。我们也没有足够的数据来了解有利于Dietz深裂谷发展、稳定和生长的条件，并导致形成旋转的加拉帕戈斯微板块。为了检验裂纹相互作用模型的适用性，将填补Dietz深裂谷沿线多波束测深数据中的大空白，并首次绘制出预测到~5My的南方三重结的踪迹。这些数据将有助于回答关于加拉帕戈斯三交界区运动学和岩石圈对应力的响应的几个悬而未决的问题。这一结果应适用于其他大洋三联结，并适用于正在形成微板块和过去已形成微板块的大洋中脊。因此，这项研究计划将填补我们在了解板块构造基本过程和地球海洋地壳演化方面的重要空白。广泛影响：该项目包括在海上和陆地上培训一名博士生。首席研究员每年在WHOI招待高中生，向学生介绍研究人员、新理论和数据。将收集的数据将是与学生进行演示和讨论的理想选择。邮轮报告将在邮轮返回后立即提供；他处理的水深、侧扫和磁力数据以及任何衍生产品将立即向更广泛的科学界和公众提供。原始多波束数据将被发送到Ridge 2000多波束合成站点，作为其一般测深数据库的一部分。最后，世界卫生组织同意捐助资金，以支付制作加拉帕戈斯三重结合部地区演变动画片的费用。将要开发的模型很难概念化，特别是对学生和普通公众来说。动画将极大地帮助描述和传播这项工作的结果。

OCE-0751831Intellectual Merit: The overall goals of this work are to understand how deformation is distributed at tectonic plate triple junctions, in general, and to elucidate the kinematic evolution of the Galapagos triple junction, in particular. The research program includes a 5-day multibeam bathymetry survey and concurrent magnetometer survey at the Galapagos triple junction, a ridge-ridge-ridge (RRR) triple junction where the Cocos, Nazca, and Pacific plates meet, separated by the Galapagos microplate. The specific goals are to 1) determine whether the stresses associated with the propagating Cocos-Nazca (C-N) Rift control the location and stability of rifting of the lithosphere to its north and south and, 2) understand what conditions might have led to the stabilization of the southern RRR triple junction at Dietz Deep Rift and the subsequent development of the rotating Galapagos microplate. A secondary goal is to place additional constraints on the rotation rate of the Galapagos microplate, which is still a matter of debate. North of the C-N Rift there has been a succession of transient rifts and triple junctions with the EPR. A simple crack interaction model predicts that the locations of these northern rifts are controlled by the distance of the tip of the C-N Rift to the EPR. The model also predicts that tensile stresses should be symmetrical about the Rift, and thus, transient rifts could occur south of the C-N Rift. Currently, this is not the case: to the south the Galapagos microplate has been stable for ~1 My. No data have been collected along the trace of the southern triple junction prior to the formation of the microplate, however, to assess whether there was a symmetrical occurrence of multiple jumping rifts then. Nor do we have sufficient data to understand the conditions that favored the development, stabilization and growth of Dietz Deep Rift and led to the formation of the rotating Galapagos microplate. To test the applicability of the crack interaction model, large gaps in the multibeam bathymetry data along the Dietz Deep Rift will be filled, and for the first time the trace of the predicted southern triple junctions out to ~5 My will be mapped. These data will help to answer several outstanding questions about the kinematics of the Galapagos triple junction region and the response of the lithosphere to stress. The results should be applicable to other oceanic triple junctions and applicable to mid-ocean ridges where microplates are forming and have formed in the past. As such this research program will fill in important gaps in our understanding of fundamental processes of plate tectonics and of the evolution of the Earth's oceanic crust.Broader Impacts: This project includes training of a Ph.D. student both at sea and on shore. The Principal Investigator hosts high school students at WHOI every year to introduce students to researchers, new theories and data. The data that will be collected will be ideal for presentations and discussions with the students. The cruise report will be made available immediately upon return from the cruise; and he processed bathymetry, sidescan, and magnetic data as well as any derived products will be made available immediately, to the wider scientific community and public. The raw multibeam data will be sent to the Ridge 2000 multibeam synthesis site as part of their general bathymetric database. Finally, WHOI has agreed to contribute funds to cover the costs of producing animations of the evolution of the Galapagos triple junction region. The models that will be developed are hard to conceptualize, especially for students and the general public. Animations will aid tremendously in describing and disseminating the results of this work.