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

9612111 Mahoney 该项目旨在继续研究世界上最大的海洋高原——西南太平洋的翁通爪哇高原（OJP）的起源和演化。 先前资助的研究补充了海洋钻探计划 (ODP) 钻探的海底 OJP 熔岩工作，重点关注所罗门群岛圣伊莎贝尔和马莱塔的高原基底部分。 本研究涉及以下任务。 实地考察：在马基拉南部和东南部进行详细的地层控制采样，预计将成为马基兰剖面的最深处。 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 熔岩，并确定 34 Ma 和 64 Ma 事件的显着性和厚度。 地球化学和岩石学：需要系统的主量元素和微量元素以及 Nd-Pb-Sr 同位素分析来定义 Makiran 地球化学地层学；特别是，OJP型熔岩随深度的地球化学变化、大致MORB状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（PGE）：先前的研究结果表明，来自 Malaita 和 ODP 钻探地点的熔岩富含亲铁元素 W 和 Mo，并且可能表明 OJP 地幔源的核幔边界起源。 对这一假设的进一步评估需要确定 OJP 熔岩子集的超嗜铁 PGE 丰度。

9612111 Mahoney 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.