Collaborative Research: Determining Triggers for Subduction Accretion and Tectonic Erosion in a Mesozoic Accretionary Complex, Alaska

当沉积物被收集时形成增生棱柱（即，在俯冲洋板块的下降边缘复杂变形。增生棱柱体在地质记录中提供了会聚的证据，是大陆地壳生长的重要机制。俯冲带中的一些增生棱柱体经历了长时间的侵蚀，而不是增生，这使得PI建议调查增生与侵蚀的触发因素。阿拉斯加的楚加奇河一直被认为是增生棱柱的典型例子。PI将与岩石类型的变化在增生棱镜在北美的主要构造事件。构造地质学和碎屑锆石年龄将用于确定这些变化是否代表不同的增生事件或增生的连续性。 他们将研究复理石，利用区域地质作为沉积物供应的代理来限制其增生历史。这个项目将阐明俯冲侵蚀的过程，影响地球内部地球化学循环的一般模型。 地质学家早就认识到，地球的许多特征以及自然灾害的原因都与大型构造板块在俯冲期间移入地球内部的过程有关。 俯冲导致火山活动，如在瀑布中看到的，俯冲导致有史以来最大的地震，如1964年在阿拉斯加。研究俯冲板块上方的沉积物将有助于我们理解这一俯冲过程。 此外，增生棱柱体有可能成为矿床的宿主，并可能提供一种会加剧全球变暖的甲烷来源。该项目还将帮助我们了解阿拉斯加的历史，并为美国西南部少数民族服务机构的本科生和研究生提供教育。

Accretionary prisms form as sediments are collected (i.e., accreted) and complexly deformed at the down-going edge of a subducting oceanic plate. Accretionary prisms provide evidence of convergence in the geologic record and are a significant mechanism for the growth of continental crust. Some accretionary prisms in subduction zones experience long periods of erosion, rather than accretion, which has led the PIs to propose investigating the triggers for accretion vs. erosion. The Chugach terrane in Alaska has long been considered as a type example of an accretionary prism. The PIs will relate rock-type variations in the accretionary prism to major tectonic events in North America. Structural geology and detrital zircon ages will be used to determine if these variations represent distinct accretionary episodes or a continuum of accretion. They will study the flysch to constrain its accretionary history using regional geology as a proxy for sediment supply. This project will elucidate processes of subduction erosion that impact general models of geochemical cycling in the Earths interior. Geologists have long realized that many of the features of the Earth, as well as the causes of natural hazards, are related to the processes by which the large tectonic plates move into the interior of the Earth during subduction. Subduction leads to volcanism, such as that seen in the Cascades, and subduction caused the largest earthquakes ever recorded, such as in Alaska in 1964. Studying the sediment accreted above the subducting plate will help us understand this subduction process. In addition, accretionary prisms have the potential to host mineral deposits and could provide a source of methane that would enhance global warming. This project will also help us to understand the history of Alaska and provide for the education of undergraduate and graduate students at minority-serving institutions in the southwest U.S.