Accomplishment Based Renewal: Geochemical Evolution of the Mantle

由地球内部流动驱动的融化过程决定了火山活动的特征和危险程度。这项研究的目的是提高我们对控制热点线的地幔动力学和控制后续火山活动的相关融化过程的理解。这将涉及对萨摩亚岛链若干火山的斑晶中的橄榄岩捕虏体和熔体内含物进行同位素研究，使用原位离子探针和激光烧蚀- icp /MS技术，以及从构造限制中吸收信息。研究结果将揭示地球化学非均质的成因、演化、分布和岩性性质，以及这些区域的熔融和熔体提取动力学。它还解决了萨摩亚热点是否是深部地幔柱的表现。需要验证的一个假设是，萨摩亚地区重新恢复的火山活动是否与俯冲的汤加板块向东滚动时撕裂的迁移有关。全面的地球化学研究和对来自七个岛屿和海底山的玄武岩的测年将被用来检验情况是否如此。这项工作的更广泛影响包括对研究生的支持，以及对马萨诸塞州伍兹霍尔海洋研究所（WHOI）清洁实验室/质谱仪同位素设施的分析基础设施的支持，该设施被许多地球科学界成员用作开放式实验室设施。在过去三年中，该设施为32多名学生和工作人员提供了分析专业知识和基础设施，其中约一半来自世卫组织，一半来自其他机构。在奖励期内设计的新分析协议将在互联网上公布，供公众查阅。资金还将帮助完成对萨摩亚群岛的地震研究，在这项研究中，萨摩亚的高中学生和教师将接受地震台站运行、操作和维护方面的培训。地震作业也将被纳入他们的课堂作业。该PI还将帮助在深部地球研究合作研究所举办为期三周的研讨会，将地震学、矿物物理学、地球化学和地球动力学的教师和学生聚集在一起。

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.