Evolution of Intraplate Volcanism in a Diffuse Igneous Province: A Case Study of the Pribilof Islands, Alaska

弥漫性火成岩省板内火山活动的演化：以阿拉斯加普里比洛夫群岛为例

• 批准号: 0439676
• 负责人: Todd Feeley
• 金额: --
• 依托单位: Montana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0439676&HistoricalAwards=false
• 关键词: Evolution; Intraplate; Volcanism; Diffuse; Igneous

This proposal is for an integrated field, 40Ar/39Ar dating, geochemical, isotopic, and petrologic study of volcanism in the Pribilof Islands, Alaska. The two principal Pribilof Islands, St. Paul and St. George, are key volcanic fields in the little studied Bering Sea basalt province (BSBP). The BSBP is an example of a 'diffuse igneous province,' a newly recognized and poorly understood type of intraplate volcanism. The Pribilof Islands have been selected for this study because they allow investigation of two major BSBP volcanic fields in a setting where factors such as lithospheric thickness and composition, distance from the Aleutian arc front, and other tectonic factors are essentially constant. This in turn allows assessment of whether differences exist in the evolution of the centers due to factors such as structural evolution, mantle and crustal mass balance involved in magmatism, and magma reservoirs and plumbing systems. The specific objectives of the project are to 1) document the volcanic and geologic evolution of the Pribilof Islands through detailed geologic mapping, sampling, and 40Ar/39Ar dating; 2) identify any temporal trends in composition through geochemical analyses of samples whose ages are well constrained; 3) determine the geometry and timing of faulting on the islands and its influence on eruptive activity and localization of distinct vent types; and 4) obtain suitably complete chemical (XRF and ICP-MS), isotopic (Sr, Nd, Pb, and O), and petrologic data for the volcanic rocks and included xenoliths so that the nature of the mantle and crustal source rocks and parent magmas can be constrained, the degrees of partial melting estimated, and the petrogenesis of the magmas determined. A significant aspect of this work is that there are several broad impacts that extend well beyond understanding the petrology of the volcanic rocks. These impacts draw from the important human and wildlife communities on the Pribilof islands. Notable aspects are that the islands host the largest Aleut communities on earth, are the seasonal breeding grounds for over half of the world's northern fur seals, and are the nesting sites for nearly three million seabirds. It is likely that differences in the distributions of these populations among the islands reflect the timing and migration of Pleistocene to Holocene volcanism and faulting in the region. Better understanding of the geologic evolution of the Pribilof Islands will therefore permit greater insight into the dominant controls on the contrasting geomorphology of each island and their contrasting wildlife and human populations.

该提案旨在对阿拉斯加普里比洛夫群岛的火山活动进行综合领域、40Ar/39Ar 测年、地球化学、同位素和岩石学研究。两个主要的普里比洛夫群岛，圣保罗岛和圣乔治岛，是鲜为人知的白令海玄武岩省 (BSBP) 的重要火山区。 BSBP 是“弥漫火成岩省”的一个例子，这是一种新近被认识但知之甚少的板内火山活动类型。 普里比洛夫群岛被选用于这项研究，因为它们允许在岩石圈厚度和成分、距阿留申岛弧前缘的距离和其他构造因素基本恒定的环境中调查两个主要的 BSBP 火山田。 这反过来又可以评估中心的演化是否因结构演化、岩浆作用涉及的地幔和地壳质量平衡、岩浆储层和管道系统等因素而存在差异。 该项目的具体目标是 1) 通过详细的地质测绘、采样和 40Ar/39Ar 测年记录普里比洛夫群岛的火山和地质演化； 2) 通过对年龄受到严格限制的样品进行地球化学分析，确定成分的任何时间趋势； 3）确定岛屿上断层的几何形状和时间及其对喷发活动的影响和不同喷口类型的定位； 4）获得火山岩和捕虏体的适当完整的化学（XRF和ICP-MS）、同位素（Sr、Nd、Pb和O）和岩石学数据，以便可以约束地幔和地壳烃源岩和母岩浆的性质，估计部分熔融程度，并确定岩浆的岩石成因。 这项工作的一个重要方面是它有几个广泛的影响，远远超出了对火山岩岩石学的理解。这些影响来自普里比洛夫群岛上重要的人类和野生动物群落。 值得注意的是，这些岛屿拥有地球上最大的阿留申群岛群落，是世界上一半以上北方海豹的季节性繁殖地，也是近 300 万只海鸟的筑巢地。这些种群在岛屿之间分布的差异很可能反映了该地区更新世到全新世火山活动和断层的时间和迁移。 因此，更好地了解普里比洛夫群岛的地质演化将有助于更深入地了解每个岛屿的对比地貌及其对比的野生动物和人类种群的主要控制因素。