Collaborative Proposal: Tectonic controls on arc evolution and petrogenesis, central Sierra Nevada Ancestral Cascades arc, California

合作提案：构造控制弧演化和岩石形成，内华达山脉中部祖先喀斯喀特弧，加利福尼亚州

• 批准号: 1917361
• 负责人: Cathy Busby
• 金额: $ 38.85万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1917361&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Tectonic; controls; arc

Recent studies of active volcanoes show that volcanic eruptions are often triggered by earthquakes, which occur in response to plate tectonic forces. But the active faults on such volcanoes cannot be directly examined as they are deeply buried by sediments and earlier erupted volcanic materials. The PIs of this study have discovered three Miocene-age volcanic centers in eastern California, in a region called the Walker Lane that, through uplift and erosion, have exposed the rarely-seen roots of Cascade volcanoes. Their work has both scientific and societal broader impacts. First, because the active Lassen Volcanic Center in northern California is also in the Walker Lane region, their proposed work will be directly applicable to understanding eruption triggering mechanisms there, and at other active Cascade volcanoes. Their recent work has also uncovered the largest volcanic eruption rates known in either the modern or ancient Cascades, and their new work will delimit the tectonic conditions that allow for very large volcanic eruptions to occur. In addition, the PIs will be training a new generation of scientists. Fresno State undergraduate students will be involved in all aspects of the work. They are mostly first generation college students, and are often from under-represented groups and low income families. This NSF support is crucial to bringing research experiences to an underserved community. Through the Fresno State-University of California Davis collaboration, Fresno State students will have the opportunity to collaborate with a PhD student as well as undergraduate field and lab assistants at UC Davis. Students will take the lead not only on research projects, but on presentations at professional meetings, and will be co-authors or lead authors on papers. Most Fresno State students will also serve California's Central Valley as Geologists after graduation, working on projects that range from earthquake hazards to groundwater quality. This early support for their research experiences thus pays dividends to the Central Valley many years after the grant is over. The project is supported by both the Petrology & Geochemsitry and Tectonics programs.The ancestral Cascade volcanoes of central California that the PIs and their students will study are the ancient analogs of active volcanoes, such as Lassen Peak and Mt Shasta in northern California, or Mt. St. Helens in Washington. The ancestral Cascades formed from about 16 to 5 million years ago and have been uplifted at the eastern edge of the Sierra Nevada Mountain range. Uplift and erosion have exposed 5 km of structural relief on three volcanic centers. The PIs will take advantage of these deep exposures to map the geologic faults that allowed these ancestral Cascade volcanoes to develop. Their earlier work showed that volcanoes develop in what are called transtensional basins; the faults that form these basins allow pathways for magmas to reach the surface. Their new geologic maps and age dates will constrain the timing of both fault activity and volcanic eruptions, and will allow a test whether the volume and style (explosive vs. effusive) of volcanic eruptions is directly related to the magnitude of fault activity. One of their hypotheses is that episodes of active transtensional faulting will allow deeper, hotter magmas to be erupted. The PIs will analyze the compositions of the lava flows, and use thermodynamic models, to determine whether the magmas were stored in deep or shallow reservoirs prior to eruption. The PIs have also discovered a suite of lavas that represent the single largest eruption rates ever recorded in either the modern or ancient Cascades. Their new data will determine whether such large eruptions tapped sources that are unusually deep or hot, and whether such episodes are controlled by fault activity. With these results, it may be possible to examine earthquakes at modern volcanoes to predict eruption volume and style.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

对活火山的最新研究表明，火山喷发通常是由地震触发的，这是响应板块构造力而发生的。但是，由于被沉积物和早期爆发的火山材料深深掩埋，因此无法直接检查此类火山上的活动断层。这项研究的PI在加利福尼亚州东部发现了三个中新世时代的火山中心，该地区在一个名为Walker Lane的地区，通过隆起和侵蚀，它揭露了喀斯喀特火山的鲜明的根源。他们的工作既具有科学和社会的广泛影响。首先，由于加利福尼亚北部的主动拉森火山中心也在沃克巷地区，因此他们的拟议工作将直接适用于了解那里的喷发触发机制以及其他活跃的级联火山。他们最近的工作还揭示了现代或古老的级联反应中最大的火山喷发率，他们的新工作将划定构成允许发生非常大的火山喷发的构造条件。此外，PI将培训新一代科学家。弗雷斯诺州本科生将参与工作的各个方面。他们主要是第一代大学生，通常来自代表性不足的群体和低收入家庭。这种NSF的支持对于将研究经验带给服务不足的社区至关重要。通过加利福尼亚戴维斯合作的弗雷斯诺州立大学，弗雷斯诺州立大学的学生将有机会与加州大学戴维斯分校的博士生以及本科生和实验室助手合作。学生不仅将领导研究项目，而且会在专业会议上进行演讲，并将成为论文的合着者或主要作者。毕业后，大多数弗雷斯诺州立大学的学生还将为加利福尼亚的中央山谷服务，作为地质学家，从事从地震危害到地下水质量的项目。因此，对他们的研究经验的这种早期支持在赠款结束后的许多年后向中央山谷带来了收益。该项目得到了岩石学和地球化学和构造计划。祖先的喀斯喀特山脉成立于大约16到500万年前，在内华达山脉山脉的东部边缘被振奋。隆起和侵蚀已在三个火山中心暴露了5公里的结构浮雕。 PI将利用这些深层暴露来绘制允许这些祖先级联火山发展的地质断层。他们的较早作品表明，火山在所谓的横向盆地中发展。形成这些盆地的断层允许岩浆到达表面的途径。他们的新地质图和年龄日期将限制断层活动和火山喷发的时间，并将允许测试火山喷发的体积和样式（爆炸性与爆炸性）是否与断层活动的幅度直接相关。他们的假设之一是，主动旋转断层的发作将使更深，更热的岩浆爆发。 PI将分析熔岩流的组成，并使用热力学模型来确定岩浆在喷发前是否存储在深处或浅水储层中。 PI还发现了一套熔岩套件，代表了现代或古代级联反应有史以来最大的爆发率。他们的新数据将确定如此大的喷发是否挖掘出异常深或热的来源，以及这些发作是否受断层活动控制。通过这些结果，可能可以检查现代火山的地震以预测喷发量和风格。该奖项反映了NSF的法定任务，并且使用基金会的知识分子优点和更广泛的影响审查标准，被认为值得通过评估来提供支持。