Expediting the Identification, Analysis, and Interpretation of Paleogene Volcaniclastic Facies at IODP Site U1438, Expedition 351

伊豆-博宁-马里亚纳(IBM)系统是2014年国际海洋发现计划(IODP)第350、351和352次考察的重点。这些考察旨在回答关于大洋内部背景下会聚边缘启动和地壳发展的基本板块构造过程的问题。拟议的研究涉及351次探险的主要目标，特别是上覆地层段记录的岩浆弧启动和演化史。在探险期间，取了1.6公里长的火山/沉积段的岩心。该岩心记录了始新世至渐新世的地层记录，包括俯冲的开始、岩浆弧的启动、弧的发展和弧的衰落？当弧裂陷导致四国盆地的海底扩张和弧岩浆活动轴向东迁移到日本南部的现在位置时。将对岩芯的沉积学和沉积岩石学进行详细分析。这些分析将为沉积序列提供对火山源(S)的性质、喷发机制、接近性和岩浆演化的洞察。沉积相分析包括基于船上岩心描述和来自离散样品的岩石学检查的成分和结构信息的综合，对这些沉积物产生并然后运往盆地的过程进行评估。结果以详细的地层柱状和相图进行了列表和总结。结果将与巡航后对特定矿物和玻璃组分的地球化学和同位素分析、孔隙水地球化学、成岩研究和测井数据的其他研究相结合。这项研究直接涉及IODP 2013-2023年科学计划中的一个专题，也涉及NSF GeoPrISMS关于俯冲旋回和变形倡议的科学计划。因此，这项研究的结果在科学上与全球广大地球科学家受众有关，并对理解俯冲起始和岩浆弧发展是基本的。

The Izu-Bonin-Mariana (IBM) system was the focus of International Ocean Discovery Program (IODP) Expeditions 350, 351, and 352 in 2014. These expeditions were designed to answer questions about the fundamental plate-tectonic processes of convergent-margin initiation and crustal development in intra-oceanic settings. The proposed research addresses primary objectives for Expedition 351, specifically the history of magmatic arc initiation and evolution as recorded in the overlying stratigraphic section. During the expedition, a 1.6 km volcanic/sedimentary section was cored. This core records the Eocene to Oligocene stratigraphic record, including the inception of subduction, initiation of the magmatic arc, arc development, and arc decline ? when arc rifting led to seafloor spreading in the Shikoku Basin and eastward migration of the axis of arc magmatism to its present position south of Japan. A detailed analysis of the sedimentology and sedimentary petrology of the core will be performed. The analyses will provide insights into the nature, eruption mechanism, proximity, and magmatic evolution of the volcanic sources (s) for the sedimentary succession. The sedimentary facies analysis includes an assessment of the processes by which these sediments were produced and then transported to the basin, based on integration of shipboard core description and compositional and textural information from petrographic examination of discrete samples. Results are tabulated and summarized in detailed stratigraphic columns and facies motifs. Results will be integrated with other post-cruise studies of specific mineral and glass component geochemistry and isotopic analyses, pore water geochemistry, diagenetic studies, and logging data. The research directly addresses a topic featured in the IODP 2013-2023 Science Plan, but also the NSF GeoPRISMS Science Plan for the Subduction Cycles and Deformation initiative. Thus, results from this study are scientifically relevant to a broad global audience of geoscientists and are fundamental to the understanding of subduction initiation and magmatic arc development.