The Diversity of Basic Magmas in a Continental Volcanic Arc and its Relationship to Tectonism

在过去十年的野外工作中，在西墨西哥火山带的弧前地区发现了Plio-第四纪富含钾和水的基性熔岩喷发（图2），与主要的钙碱性安山岩中心火山同时代。这种火山活动与哈利斯科地块内部和边缘的裂谷作用的联系（图2），可能对沿大陆辐合边缘的岩浆和构造制度具有一般意义。本项目将研究构造作用、火山中心分布、岩浆输出速率和成分多样性之间的关系，以更好地了解岩浆源区非均质性的程度和规模，以及影响岩浆上升和喷发的因素。拟议的实地工作将侧重于墨西哥中部5万平方公里地区的火山活动，特别是墨西哥谷。这个地区有超过400个单一成因的火山锥、火山流和其他喷发中心，人们对它们知之甚少。全面研究该火山活动的时空分布是建立岩浆成因和多样化模型的关键。该地区也是墨西哥人口最密集的地区之一，因此，私人调查团将与墨西哥国立自治大学的墨西哥科学家合作进行的火山危害评估将有助于提高其重要性。

Field work in the last decade has led to the discovery of Plio- Quaternary eruptions of potassium- and water-rich basic lavas in the fore-arc region of the western Mexican Volcanic belt (Fig. (Fig. 2), contemporary with the main calc-alkaline andesitic central volcanoes. The association of this volcanism with rifting, both within and at the margin of the Jalisco block (Fig. 2), may have general implications for the magmatic and tectonic regimes along a continental convergent margin. This project will investigate the relationships between tectonism, distribution of volcanic centers, magma output rates, and compositional diversity in order to gain a better understanding of the extent and scale of the heterogeneity of magma source regions, as well as the factors which influence the ascent and eruption of magma. The proposed field work will focus on volcanism in a 50,000 km2 region in central Mexico, particularly the Valley of Mexico. This region contains over 400 monogenetic cones, flows, and other eruptive centers about which little is known. A comprehensive study of the temporal and spatial distribution of this volcanism is a crucial constraint on models of magma genesis and diversification. This region is also one of the most densely populated in Mexico so that the assessment of volcanic hazards, which the P.I.s will conduct in collaboration with Mexican scientists at UNAM, will contribute to its significance.