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

合作研究：确定阿拉斯加中生代增生杂岩中俯冲增生和构造侵蚀的触发因素

• 批准号: 0809609
• 负责人: Terry Pavlis
• 金额: $ 7.83万
• 依托单位: University of Texas at El Paso
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809609&HistoricalAwards=false
• 关键词: Collaborative; Research; Determining; Triggers; Subduction

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.

当沉积物在俯冲海洋板块的下降边缘聚集（即吸积）并发生复杂变形时，就会形成吸积棱柱。增生棱柱提供了地质记录中聚合的证据，并且是大陆地壳生长的重要机制。俯冲带中的一些吸积棱柱经历了长期的侵蚀，而不是吸积，这使得 PI 提议调查吸积与侵蚀的触发因素。阿拉斯加的楚加奇地体长期以来一直被认为是吸积棱柱的典型例子。 PI 将把增生棱柱中的岩石类型变化与北美的主要构造事件联系起来。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连续的增生过程。 他们将利用区域地质学作为沉积物供应的代理来研究复理石，以限制其增生历史。该项目将阐明影响地球内部地球化学循环一般模型的俯冲侵蚀过程。 地质学家很早就意识到，地球的许多特征以及自然灾害的原因都与俯冲过程中大型构造板块移入地球内部的过程有关。 俯冲会导致火山活动，例如喀斯喀特山脉中所见的火山活动，俯冲引发了有史以来最大的地震，例如 1964 年在阿拉斯加发生的地震。研究俯冲板块上方积聚的沉积物将有助于我们了解这一俯冲过程。 此外，吸积棱柱有可能蕴藏矿藏，并可能提供甲烷来源，从而加剧全球变暖。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。