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Wrangell火山带位于一个复杂的构造环境中，在这个环境中，一个海洋高原（Yakutat地块）目前正以一个非常低的角度在阿拉斯加下面碰撞和俯冲。在东面，一个巨大的转换断层系统，迪纳里断层，束缚着这个俯冲高原的边缘，一个主要的火山链，弗兰格尔火山带，在过去的2500万年里建立起来，标志着这个交叉点。这种连接在现代辐合边缘环境中很常见，由此产生的火山带既记录了板块前缘相对位置的变化，也记录了板块上部沿走滑断层的平移。在这些复杂的环境中产生熔岩的过程人们知之甚少。本课课组旨在通过对弗兰格尔火山带的地质、火山岩化学成分和年代学的综合研究，破解该火山带火山岩的起源。研究结果将为火山链如何在如此复杂的构造环境中发展提供新的认识。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)计划让代表性不足的少数民族学生参与STEM；(2)通过在当地社区的演讲和为Wrangell-St.开发解释性材料，提高公众的科学素养和公众对科学技术的参与。伊莱亚斯国家公园和保护区；(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。本项目研究了阿拉斯加Wrangell火山带25 Ma弧转换岩浆带的地球化学喷发演化。该带被一条主要的走滑断裂，即德纳里断裂系统所横断，位于雅库特平板的边缘和前缘之上。研究人员将从弗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。他们将确定主要和微量元素组成，整个岩石Sr， Nd， Pb和Hf，锆石Hf同位素浓度，基岩和碎屑样品的40Ar/39Ar和U/Pb年代学。该项目的具体目标是：(1)确定Wrangell火山带岩浆活动的时空历史；(2)揭示走滑断裂与板块熔融作用在该板块边缘火山带地球化学演化中的联系。这些数据将与地质填图相结合，为平板前缘向内推进时沿弧形转换结的板块边缘岩浆活动的发育以及走滑断层与岩浆产物地球化学的关系提供重要的新约束。

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.