Accomplishment Based Renewal: Geochemical Evolution of the Mantle

地球内部流动驱动的融化过程决定了火山活动的性质和危险程度。这项研究旨在提高我们对控制热点线理的地幔动力学以及控制后续火山活动的相关熔融过程的理解。这将涉及利用原位离子探头和激光烧蚀-电感耦合等离子体质谱技术对萨摩亚岛链若干火山斑晶中的橄榄岩包裹体和熔融包裹体进行同位素研究，并吸收来自构造制约因素的信息。研究结果将有助于揭示地球上化学不均质性的成因、演化、位置和岩性，以及这些区域的熔融和熔融提取动力学。它还讨论了萨摩亚热点是否是深地幔热柱的表现。一个有待检验的假设是，萨摩亚地区的火山活动复苏是否与俯冲的汤加板块向东滚动时撕裂的迁移有关。将使用对其中七个岛屿和海山的玄武岩进行全面的地球化学研究和测年来测试情况是否属实。这项工作的更广泛影响包括对研究生的支持，以及在马萨诸塞州伍兹霍尔海洋研究所(WHOI)的清洁实验室/质谱仪同位素设施方面对分析基础设施的支持，该设施被地球科学界的许多成员用作开放式实验室设施。在过去三年中，该机构为32多名学生和工作人员提供了分析专业知识和基础设施，其中约一半来自世界卫生组织，一半来自其他机构。在授标期间设计的新分析方案将张贴在互联网上供公众查阅。资金还将帮助完成对萨摩亚群岛的地震研究，在该研究中，萨摩亚高中生和教师接受了地震台站运行、操作和维护方面的培训。地震作业也将纳入他们的课堂作业。这个PI还将帮助在地球深部研究合作研究所举办一个为期3周的研讨会，将地震学、矿物物理学、地球化学和地球动力学的教职员工和学生聚集在一起。

Melting processes driven by flow within the Earth determine the character and hazard level of volcanic activity. This research targets improving our understanding of the mantle dynamics that control hotspot lineations and the associated melting processes that control subsequent volcanism. This will involve an isotopic study of peridotite xenoliths and melt inclusions in phenocrysts from a number of volcanoes in the Samoan Island chain, using in situ ion probe and laser ablation-ICP/MS techniques, as well as assimilating information from tectonic constraints. Results of the research will shed light on the genesis, evolution, placement and lithologic nature of chemical heterogeneities in the Earth and the dynamics of melting and melt extraction from these domains. It also addresses whether the Samoan hotspot is a manifestation of a deep mantle plume. One hypothesis to be tested is whether rejuvenated volcanism in the Samoa area is related to the migration of the tear in the subducting Tonga slab as it rolls back to the east. Comprehensive geochemical studies and dating of basalts from seven of the islands and seamounts will be used to test whether this is the case. Broader impacts of this work include the support of graduate student and support of analytical infrastructure in terms of the clean lab/mass spectrometer isotope facility at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts, which is used as an open-door laboratory facility by many members of the geoscientific community. Over the last three years this facility has provided analytical expertise and infrastructure for more than 32 students and staff, about half from WHOI and half from other institutions. New analytical protocols devised during the award period will be posted for public access on the Internet. Funding will also help complete a seismic study of the Samoan Islands, in which Samoan high school students and teachers are trained in the running, operation, and maintenance of seismic stations. The seismic work will also be incorporated into their class work. This PI will also help run a 3-week workshop at the Cooperative Institute for Deep Earth Research to bring together faculty and students from seismology, mineral physics, geochemistry and geodynamics.