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.

该建议是一个综合的领域，40 Ar/39 Ar定年，地球化学，同位素和岩石学研究的火山在Pribilof群岛，阿拉斯加。两个主要的Pribilof群岛，圣保罗和圣乔治，是白令海玄武岩区（BSBP）的关键火山区。 BSBP是一个“弥散火成岩省”的例子，这是一种新认识的板内火山作用类型，但人们对其了解甚少。 选择普里比洛夫群岛进行这项研究，是因为它们允许在岩石圈厚度和成分、距阿留申弧前缘的距离和其他构造因素基本恒定的情况下，对两个主要的BSBP火山场进行调查。 这反过来又允许评估是否存在差异的中心，由于结构演化，地幔和地壳质量平衡参与岩浆活动，岩浆库和管道系统等因素的演变。 该项目的具体目标是：（1）通过详细的地质测绘、取样和40 Ar/39 Ar年代测定，记录普里比洛夫群岛的火山和地质演变;（2）通过对年代受到严格限制的样品进行地球化学分析，查明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，以及它对喷发活动和不同喷口类型定位的影响; 4）获得火山岩和包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，以便限制地幔和地壳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，有几个广泛的影响，远远超出了理解火山岩的岩石学。这些影响来自普里比洛夫群岛上重要的人类和野生动物社区。 值得注意的是，这些岛屿拥有地球上最大的阿留申人社区，是世界上一半以上的北方海狗的季节性繁殖地，也是近300万只海鸟的筑巢地。这些人口在岛屿之间的分布差异可能反映了该地区更新世至全新世火山活动和断层活动的时间和迁移。 因此，更好地了解普里比洛夫群岛的地质演变将有助于更深入地了解对每个岛屿的对比地貌及其对比野生动物和人口的主要控制。