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

地球是一个充满活力的星球。它的表面在构成巨大构造板块边界的洋脊和俯冲带不断地产生和破坏。 这些过程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层。 在此基础上是地球地幔的循环，主要表现为沿着洋脊的上涌和地幔柱。后者是向上的流动，产生地幔热点，如夏威夷和冰岛。当洋脊经过地幔热点附近时，如在大西洋的冰岛和亚速尔群岛，以及在印度洋的马里恩热点，洋脊被大大抬高，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，火山热点是由深深扎根于地幔中的地幔柱产生的，并且该地幔柱的流动部分转向邻近的洋脊，在那里它成为熔岩喷发的源头。 然而，海洋上升之间存在很大差异，不同的过程可能是造成马里恩热点的原因，马里恩热点是南非东南约1,000英里处的一个偏远的火山特征，位于非洲和南极构造板块的边界。一个由德国，美国，与中国科学家合作，正在共同验证一个新的假设，即马里恩隆起代表了古冈瓦纳超大陆分裂期间漂浮在地球深处的一块异常地幔的融化。传统的深地幔柱假说预测增厚的地壳所有沿着上升，而重熔冈瓦纳地幔预测薄或失踪地壳沿着脊，与孤立的广泛分布的本地岩浆中心，与最厚的地壳位于交叉处的地幔熔融异常与脊。 该奖项支持美国参与德国-美国-中国合作巡航，这是两个探险计划中的第二个，其中第一个由美国科学家领导。美国科学队将指导对布维岛以北发现断裂带以西的西南印度洋海岭进行地球物理磁学、重力和多波束测绘，并将利用这些数据，结合德国研究船索内号上的岩石疏浚和岩石取样结果，绘制出直接暴露在海底的地幔范围，并限制未暴露的地壳厚度。 它们将描述海底地形和构造与东太平洋海隆和大西洋中脊等岩浆作用较强的洋脊的差异。 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知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.