ROW: Geochemical Evolution of Alkaline and Peralkaline Magmatism Associated with Oceanic Rift Failure: Revillagigedo Islands, Mexico

东太平洋的索科罗群岛和圣本尼迪克托群岛之所以引人注目，是因为它们位于最近被遗弃的扩张中心(-3.15 Ma前)的轴线上，但仍在火山活动中。此外，索科罗岛的独特之处在于，它是太平洋上唯一一个以盐碱为主的海洋岛屿。这项研究将记录索科罗群岛和圣本尼迪克托群岛在海脊破裂背景下的地质和地球化学史。主要元素和微量元素、40Ar-39Ar年代学、全岩、玻璃和斑晶的锶、钕、铅和钍同位素分析将在该地区的海底地形高处进行。这项研究的目的是：1)描述索科罗岛和圣本尼迪克托群岛的地球化学演化；2)限制索科罗岛下岩浆库的深度和可能的体积；3)证明成分分层与镁铁质补给在解释索科罗岛喷发历史和盐性过碱性岩浆起源方面的相对重要性；(4)建立现代区域岩浆活动的源区与废弃的洋中扩张中心源区之间的时间和地球化学关系。

Socorro and San Benedicto Islands in the Eastern Pacific Ocean are remarkable because they are located on the axis of a recently abandoned spreading center (-3.15 Ma ago) and yet are still volcanically active. Moreover, Socorro Island is unique in being the only predominantly salic peralkaline oceanic island in the Pacific Ocean. This research will document the geologic and geochemical histories of Socorro and San Benedicto Islands in the context of ridge failure. Major and trace element, 40Ar-39Ar geochronology, and Sr, Nd, Pb, and Th isotopic analyses of whole rocks, glasses and phenocrysts will be conducted on samples from submarine topographic highs in the region. The purpose of the research is to: 1) characterize the geochemical evolution of Socorro and San Benedicto Islands; 2) constrain the depth and possibly volume of the magma reservoir beneath Socorro; 3) document the relative importance of compositional stratifications versus mafic recharge in explaining both the eruptive history of Socorro Island and the origin of salic peralkaline magmas; and 4) 4) establish the temporal and geochemical relationship between sources of recent regional magmatism and those of the abandoned mid-ocean spreading center.