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

9628252尼尔这个项目是为了继续研究世界上最大的海洋高原--西南太平洋的安通爪哇高原(OJP)的起源和演化。以前资助的研究补充了大洋钻探方案钻探的海底OJP熔岩的工作，重点是所罗门群岛圣伊莎贝尔和马莱塔的高原地下室段。本研究涉及以下几个方面的工作。野外工作：在马基拉南部和东南部进行详细的地层控制采样，预计这将是马基兰段最深的部分。40Ar-39Ar测年：需要对整个马基兰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Ma事件的意义和厚度。地球化学和岩石学：需要系统的常量元素和微量元素分析以及NdPbsr同位素分析来确定马基兰地球化学地层学，特别是OJP型熔岩的地球化学随深度的变化，广泛的类MORB玄武岩的性质和地层范围，以及两种类型夹层的性质和原因。铂族元素：以前的研究结果表明，马莱塔和ODP型钻探现场的熔岩富含亲铁元素W和Mo，可能指示了OJP地幔源区的核幔边界起源。对这一假设的进一步评估需要确定OJP熔岩子集的超铁亲铁PGE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.