Collaborative Research: Origins of the Ontong Java Plateau, SW Pacific: A Stratigraphic and Geochemical Study of Exposed Plateau Basement in the Solomon Islands, Part 2

这个项目是为了继续研究世界上最大的海洋高原——西南太平洋的Ontong爪哇高原（OJP）的起源和演变。先前资助的研究，补充了海洋钻探计划（ODP）钻探海底OJP熔岩的工作，主要集中在所罗门群岛Santa Isabel和Malaita的高原基底部分。本研究包括以下任务。实地工作：在Makira南部和东南部进行了详细的地层控制采样，预计这将是Makiran剖面最深的部分。40Ar-39Ar测年：需要对整个Makiran剖面的样品进行测年，以确定是否存在90 Ma和/或122 Ma的熔岩，并确定34 Ma和64 Ma事件的重要性和厚度。地球化学和岩石学：需要系统的主微量元素和Nd-Pb-Sr同位素分析来定义Makiran地球化学地层；特别是ojp型熔岩的地球化学随深度的变化，大致类似morb的玄武岩的性质和地层范围，以及两类玄武岩的性质和插层原因。铂族元素（PLATINUM GROUP ELEMENTS, PGEs）：前人的研究结果表明，Malaita和ODP钻探点的熔岩富含亲铁元素W和Mo，可能是OJP地幔源的核幔边界成因。对这一假设的进一步评估需要确定OJP熔岩子集的超亲铁PGEs的丰度。

9628252 Neal This project is for a continuation of research into the origin and evolution of the world's largest oceanic plateau, the Ontong Java Plateau (OJP) in the SW Pacific. Previously funded study, complementing work on submarine OJP lavas drilled by the Ocean Drilling Program (ODP), focused on plateau basement sections on Santa Isabel and Malaita, Solomon Islands. This research involves the following tasks. FIELDWORK: Detailed, stratigraphically controlled sampling in south and southeastern Makira, in what is expected to be the deepest part of the Makiran section. 40Ar-39Ar DATING: Dating of samples from throughout the Makiran section is required to determine if 90 Ma and/or 122 Ma lavas are present, and to establish the significance and thickness of the 34 Ma and 64 Ma events. GEOCHEMISTRY AND PETROGRAPHY: Systematic major and trace element, and Nd-Pb-Sr isotopic analyses are required to define Makiran geochemical stratigraphy; in particular, the geochemical variation of OJP-type lavas with depth, the nature and stratigraphic extent of the broadly MORB-like basalts, and the nature and causes of intercalation of the two types. PLATINUM GROUP ELEMENTS (PGEs): Results from previous study show that lavas from Malaita and ODP drill sites are enriched in the siderophile elements W and Mo, and may indicate a core-mantle boundary origin for the OJP's mantle source. Further evaluation of this hypotheses requires determination of abundances of the ultra-siderophilic PGEs for a subset of OJP lavas.