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

Izu-Bonin-Mariana（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会聚边缘形成和洋内地壳发展的基本板块构造过程的问题。拟议的研究解决了远征351的主要目标，特别是岩浆弧的起源和演化的历史记录在上覆地层部分。在考察期间，对一个1.6公里长的火山/沉积岩段进行了取芯。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、岩浆弧的形成、弧的发展和弧的衰退。当弧形裂谷导致四国盆地的海底扩张和弧形岩浆活动轴向东迁移到日本南部的现今位置时。将对岩心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火山源的性质、喷发机制、邻近性和岩浆演化的见解。 沉积相分析包括对这些沉积物产生并随后输送至盆地的过程进行评估，评估的基础是整合船上岩心描述以及来自离散样品岩相学检查的成分和结构信息。结果以详细的地层柱和相图案制成表格并进行了总结。研究结果将与特定矿物和玻璃成分地球化学和同位素分析、孔隙水地球化学、成岩作用研究和测井数据等其他航行后研究相结合。该研究直接解决了IODP 2013-2023科学计划中的一个主题，也是NSF GeoPRISMS俯冲周期和变形计划的科学计划。因此，这项研究的结果在科学上与全球广大的地球科学家有关，对理解俯冲的开始和岩浆弧的发展至关重要。

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.