Melt Generation Beneath the Colorado Plateau and its Transition Zones

科罗拉多高原及其过渡带下方的融化生成

• 批准号: 0810274
• 负责人: Mary Reid
• 金额: --
• 依托单位: Northern Arizona University
• 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: 2008-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0810274&HistoricalAwards=false
• 关键词: Melt; Generation; Beneath; Colorado; Plateau

A fundamental challenge for earth scientists is to understand the origin of volcanic activity not associated with plate boundaries and especially that interior to the continents. Volcanic rock chemistry provides one of the most powerful ways to probe the sources and melting mechanisms responsible for this activity and, at the same time, to gain insights into the present structure and dynamics of the continents. This grant supports an international collaboration that will produce new geochemical limits on magma generation beneath the southwestern U.S. where numerous young volcanoes sample the continent and its underlying mantle over a broad geographical region. Interpretations based on these results will be refined in the context of ongoing geophysics-based efforts such as Earthscope to arrive at internally consistent models for volcanic activity associated with the Colorado Plateau and its transition zones. Despite efforts to understand the origin of continental basalts in the southwestern U.S., disparate observations and interpretations persist for how and where melting occurs. In many cases, existing data are too piecemeal or too general to determine if and where the mantle is actively upwelling, the depths at which melts segregrate, and the chemical and physical role that mantle lithosphere plays in melt generation. This project will result in a comprehensive chemical and Th-Hf-Nd isotope characterization of young basalts from the Colorado Plateau and its transition zones. Inferences based on paired trace element and isotopic characteristics and from inversion of major element data will delimit the depth and depth interval of melting and the relative contributions of enriched and depleted sources. These constraints, as well as limits on the sizes of melt fractions, will permit a better understanding of the relationship between the structure and evolution of lithosphere and melting dynamics in the southwestern U.S.

地球科学家面临的一个基本挑战是了解与板块边界无关的火山活动的起源，尤其是与大陆内部无关的火山活动。 火山岩化学提供了最有力的方法之一来探索造成这种活动的来源和熔化机制，同时深入了解大陆目前的结构和动态。 这笔赠款支持一项国际合作，该合作将对美国西南部下方的岩浆生成产生新的地球化学限制，那里有许多年轻的火山对这片大陆及其广阔地理区域的地幔进行采样。 基于这些结果的解释将在 Earthscope 等正在进行的基于地球物理学的努力的背景下得到完善，以获得与科罗拉多高原及其过渡区相关的火山活动的内部一致模型。尽管人们努力了解美国西南部大陆玄武岩的起源，但对于融化的方式和地点仍然存在不同的观察和解释。 在许多情况下，现有数据过于零散或过于笼统，无法确定地幔是否以及在何处积极上涌、熔体分离的深度以及地幔岩石圈在熔体生成中所起的化学和物理作用。 该项目将对科罗拉多高原及其过渡带的年轻玄武岩进行全面的化学和 Th-Hf-Nd 同位素表征。 基于配对微量元素和同位素特征以及主要元素数据反演的推论将界定熔化的深度和深度区间以及富集源和枯竭源的相对贡献。 这些约束以及对熔体分数大小的限制将有助于更好地了解美国西南部岩石圈的结构和演化与熔融动力学之间的关系。