Collaborative Research: Thin Crust Over The Marion Rise: Remelting The Gondwanan Mantle II

合作研究：马里恩隆起的薄地壳：冈瓦纳地幔 II 的重熔

• 批准号: 1935837
• 负责人: Henry Dick
• 金额: $ 29.79万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-15 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1935837&HistoricalAwards=false
• 关键词: Collaborative; Research; Thin; Crust; Over

Earth is a dynamic planet. Its surface is being continuously created and destroyed at ocean ridges and subduction zones, which comprise the boundaries of the great tectonic plates. These processes create seismic and volcanic hazards as well as generating economic resources, thermal energy, and the planet's oceans and atmosphere. Underlying this is the circulation of the Earth's mantle, largely manifest by upwelling along ocean ridges, and mantle plumes. The latter are upward flows that produce mantle hotspots, such as Hawaii and Iceland. Where ocean ridges pass near mantle hotspots as at Iceland and the Azores Islands in the Atlantic, and at Marion Hotspot in the Indian Ocean, the ocean ridge is greatly elevated and has a chemical composition similar to the associated mantle hotspot. The standard scientific explanation for this is that the volcanic hotspot is created by a mantle plume rooted deep in the mantle, and that the flow of this plume is partially diverted to the adjacent ocean ridge, where it becomes the source of the lavas erupting there. However, there are large differences between ocean rises, and a different process may be responsible for the Marion Hotspot, a remote volcanic feature roughly 1,000 miles southeast of South Africa that sits at the boundary of the African and Antarctic tectonic plates. An international team, led by German, U.S., and Chinese scientists, is working together to test a new hypothesis that the Marion Rise represents the melting of a piece of anomalous mantle set adrift in the deep earth during the breakup of the ancient supercontinent Gondwana. The conventional deep mantle plume hypothesis predicts thickened crust all along the rise, while remelting the Gondwana mantle predicts thin or missing crust along the ridge, with isolated widely spaced local magmatic centers, with the thickest crust located at the intersection of the mantle melting anomaly with the ridge. This award supports the U.S. participation in a German-U.S.-China collaborative cruise, which is the second of a two expedition program, the first of which was led by the U.S. scientists. The U.S. Scientific Party will direct the geophysical magnetics, gravity, and multibeam mapping survey of the Southwest Indian Ridge west of the Discovery Fracture Zone north of Bouvet Island, and will use this data, in combination with the results of the rock dredging and ROV sampling on the German research vessel Sonne, to map out the extent of the mantle directly exposed on the seafloor, and constrain the crustal thickness where it is not exposed. They will characterize the differences in seafloor topography and tectonics from that seen at magmatically more robust ocean ridges such as the East Pacific Rise and Mid-Atlantic Ridge. In doing this, they will directly test and validate one of the two hypotheses for the origin of the Marion Rise described above.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地球是一个充满活力的星球。它的表面在洋脊和俯冲带处不断地被创造和破坏，这些洋脊和俯冲带构成了大构造板块的边界。 这些过程会造成地震和火山灾害，并产生经济资源、热能以及地球的海洋和大气。 其背后是地幔的循环，主要表现为沿着洋脊和地幔柱的上升流。后者是向上流动，产生地幔热点，例如夏威夷和冰岛。在洋脊经过地幔热点附近的地方，如冰岛和大西洋的亚速尔群岛，以及印度洋的马里昂热点，洋脊高度升高，其化学成分与相关的地幔热点相似。 对此的标准科学解释是，火山热点是由根植于地幔深处的地幔羽流形成的，并且该羽流的流动部分转移到邻近的洋脊，在那里成为熔岩喷发的源头。 然而，海平面上升之间存在很大差异，马里恩热点可能是由不同的过程造成的，马里恩热点是位于南非东南部约 1,000 英里处的一个偏远火山地貌，位​​于非洲和南极板块的边界处。由德国、美国和中国科学家领导的一个国际小组正在共同测试一个新的假设，即马里恩隆起代表着古代超大陆冈瓦纳大陆分裂期间漂浮在地球深处的一块异常地幔的融化。传统的深部地幔柱假说预测沿隆起地壳会增厚，而冈瓦纳地幔重​​熔则预测沿山脊地壳薄或缺失，局部岩浆中心间隔较远，最厚的地壳位于地幔熔融异常与地幔熔异常的交汇处。山脊。 该奖项支持美国参与德美中合作巡航，这是两次探险计划中的第二次，第一次探险计划由美国科学家领导。美国科学小组将指导对布韦岛以北发现断裂带以西的西南印度洋脊进行地球物理磁学、重力和多波束测绘调查，并将结合岩石疏浚和 ROV 采样的结果使用这些数据在德国科考船 Sonne 上，绘制出直接暴露在海底的地幔范围，并限制未暴露处的地壳厚度。 他们将描述海底地形和构造与东太平洋隆起和大西洋中脊等岩浆更坚固的洋脊所见的差异。 在此过程中，他们将直接测试和验证上述马里恩隆起起源的两个假设之一。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Shallow recycling of lower continental crust: The Mahoney Seamount at the Southwest Indian Ridge

下大陆地壳的浅层再循环：西南印度洋脊的马奥尼海山

• DOI: 10.1016/j.epsl.2022.117968
• 发表时间: 2023
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Woelki, Dominic;Salters, Vincent;Beier, Christoph;Dick, Henry;Koepke, Juergen;Romer, Rene
• 通讯作者: Romer, Rene