Evolution of the Philippine Sea Plate: Geochemical and Geochronological Studies of Pre-Oligocene Igneous Rocks

本文研究了南马里亚纳海沟斜坡上罕见的长英质和中侵入岩的成因。这些不寻常的岩石似乎代表了伊豆-波宁/马里亚纳（IBM）火山弧下的海洋地壳的中部。出乎意料的是，这些早期岩石具有岛弧地球化学特征，Pb同位素年龄表明它们的年龄为白垩纪。如果得到证实，这将表明更古老的弧或地壳碎片构成了IBM弧基底的一部分。这对IBM弧区海底的演变有重大影响，可能对整个火山弧也有重大影响。研究目标是确定这些岩石在弧演化过程中形成的时间和/或它们是否是古弧或弧的一部分，以及这些侵入单元是否促进了壳内岩浆分选和中地壳发育。将收集地球化学和同位素资料，研究侵入中地壳剖面可能的继承特征和发育情况。了解洋内弧壳的形成过程对大陆地壳的发育及其模拟具有重要意义。这项工作的更广泛影响包括对科学领域性别代表性不足的研究者和研究生的支持、国际合作以及对少数族裔服务机构教员的支持。这项工作加强了美国国家科学基金会资助的边际项目正在进行的工作。

This research addresses the origin of the unusual felsic and intermediate intrusive rocks collected from the slope of the southern Mariana Trench. These unusual rocks appear to represent the middle part of the ocean crust under the Izu-Bonin/Mariana (IBM) volcanic arc. Unexpectedly, these early rocks have an island arc geochemical signature with Pb isotope ages indicating they are Cretaceous in age. If verified, this would indicate that older arc or crustal fragments comprise some of the IBM arc basement. which has significant ramifications for the evolution of the seafloor in the IBM arc area and possibly for volcanic arcs in general. Research goals are to determine at what time during arc evolution these rocks formed and/or whether they are parts of older or arcs and if these intrusive units enhanced intracrustal magmatic differentiation and middle crust development. Geochemical and isotopic data will be collected to examine possibly inhereted features and the development of the intrusive middle crustal section. Understanding the formation of how intra-oceanic arc crust forms is critical for development of continental crust and its modeling. Broader impacts of the work include support of an investigator and graduate student from a gender under-represented in the sciences, international collaboration, and support of faculty at minority-serving institution. The work enhances work being carried out by the NSF-funded MARGINS program.