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

在过去的十年中，野外工作导致在墨西哥西部火山带的弧前地区发现了第四纪喷发的富钾和富水的基性熔岩。(图2)，与主要钙碱性安山岩中央火山同时代。这种火山活动与哈利斯科地块内部和边缘的裂谷作用(图2)的联系，可能对大陆汇聚边缘的岩浆和构造制度具有普遍意义。该项目将研究构造作用、火山中心分布、岩浆产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50,000平方公里地区的火山活动，特别是墨西哥山谷。该区域包含400多个单生锥、流和其他喷发中心，对这些中心知之甚少。对火山活动时空分布的全面研究是岩浆成因和多样化模式的关键制约因素。这一地区也是墨西哥人口最稠密的地区之一，因此，对火山灾害的评估将有助于该地区的重要性，该评估将由P.I.与UNAM的墨西哥科学家进行。

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.