Collaborative Research: Geological Constraints on ~25 Million Years of Magmatism Along an Arc-transform Junction, Wrangell Volcanic Belt, Alaska

阿拉斯加南部的兰格尔火山带位于复杂的构造环境中，海洋高原（雅库塔地块）目前正以非常低的角度与阿拉斯加碰撞并俯冲到阿拉斯加下方。在东部，一个大型转换断层系统——德纳利断层——界定了这个俯冲高原的边缘，而一条主要火山链——过去 2500 万年形成的兰格尔火山带——标志着这个交点。这种交界处在现代会聚边缘环境中很常见，由此产生的火山带记录了板片前缘相对位置的变化以及上板块沿走滑断层的平移。人们对这些复杂环境中产生熔岩的过程知之甚少。在这里，该研究小组旨在通过对兰格尔火山带的地质、火山岩化学成分和地质年代学的综合研究，破译兰格尔火山带火山岩的起源。这些结果将为火山链如何在如此复杂的构造环境中发育提供新的认识。该项目还通过以下方式造福社会或促进预期的社会成果：(1) 有计划地让代表性不足的少数族裔学生参与 STEM； (2) 通过在当地社区进行演讲和为兰格尔-圣路易斯开发解释材料，提高公众科学素养和公众对科学技术的参与。埃利亚斯国家公园和自然保护区； (3) 通过培训研究生和本科生以及支持早期职业研究人员来发展 STEM 劳动力。该项目研究了欠采样 25 Ma 弧形转变岩浆带（阿拉斯加的兰格尔火山带）的地球化学喷发演化。该带被主要的走滑断层——迪纳利断层系统横切，位于雅库塔特平板的边缘和前缘之上。研究人员将从兰格尔火山带收集基岩、碎屑砂/鹅卵石样本以及沉积学和结构数据。他们将确定主量和微量元素组成、全岩 Sr、Nd、Pb 和 Hf 以及锆石 Hf 同位素浓度，以及基岩和碎屑样品的 40Ar/39Ar 和 U/Pb 地质年代学。该项目的具体目标是：（1）确定兰格尔火山带岩浆作用的时空历史； (2)破译走滑断层作用与板片熔融作用对该板片边缘火山带地球化学演化的联系。这些数据将与地质测绘相结合，为平板前沿岩浆作用沿弧形转换交界处的发展提供重要的新约束，以及走滑断层与岩浆产物地球化学之间的关系。

The Wrangell volcanic belt in southern Alaska is situated in a complex tectonic environment where an oceanic plateau (the Yakutat block) is presently colliding with and subducting beneath Alaska at a very low angle. To the east, a large transform fault system, the Denali fault, bounds the edge of this subducting plateau and a major volcanic chain, the Wrangell volcanic belt that has been built up over the last 25 million years, marks this intersection. Such junctions are common in modern convergent margin settings and the resulting volcanic belts record both variations in relative position of the leading front of the slab and translation of the upper plate along strike-slip faults. The processes that generate lavas in these complex settings are poorly understood. Here, this research team aims to decipher the origins of the volcanic rocks in the Wrangell volcanic belt through a comprehensive study of the geology, volcanic rock chemical composition, and geochronology of the belt. The results would provide a new understanding of how volcanic chains develop in such complex tectonic settings. The project also benefits society or advances desired societal outcomes through: (1) planned involvement of students from underrepresented minorities in STEM; (2) increased public scientific literacy and public engagement with science and technology through presentations in local communities and development of interpretive materials for the Wrangell-St. Elias National Park and Preserve; and (3) development of a STEM workforce through training of graduate and undergraduate students and support of early career researchers.This project examines the geochemical-eruptive evolution of an under-sampled 25 Ma arc-transform magmatic belt, the Wrangell volcanic belt in Alaska. The belt is transected by a major strike-slip fault, the Denali fault system, and located above both the edge and leading front of the Yakutat flat slab. The researchers will collect bedrock, detrital sand/cobbles samples, and sedimentological and structural data from the Wrangell volcanic belt. They will determine major and trace element composition, whole rock Sr, Nd, Pb, and Hf, and zircon Hf-isotope concentrations, and 40Ar/39Ar and U/Pb geochronology on bedrock and detrital samples. Specific objectives of the project are to: (1) determine the temporal-spatial history of magmatism of the Wrangell volcanic belt; and (2) decipher the links between strike-slip faulting, and slab melting on the geochemical evolution of this slab edge volcanic belt. These data will be integrated with geological mapping to provide important new constraints on the development of slab edge magmatism along an arc-transform junction as the leading front of the flat slab progresses inboard and the relationship between strike-slip faults and the geochemistry of magmatic products.