The Life History of an Arc Volcano: Insights from a Collaborative, Petrologic, Paleomagnetic and Geochronologic Study

美国科学家团队对智利安第斯山脉的第四纪南部火山带（SVZ）进行了研究，他们关注于量化弧母岩浆中的地幔源成分，以及这些岩浆与弧壳相互作用的程度。地壳年龄、厚度和俯冲板块年龄的纵向变化使其成为区域研究的理想目标。该项目的主要重点是对塔塔拉-圣佩德罗（TSP） （360 S）进行非常详细和全面的调查，这是圣佩德罗-佩拉多火山群中最年轻的建筑（约150ka至全新世）。这项研究将以大量关于第四纪活动沿走向和跨走向变化的区域资料为基础。除了其成分的可变性外，总磷从其底部暴露得特别好：1公里垂直（或复合）部分（多达150个流）从锥的所有象限暴露在深冰川峡谷中。这些剖面将以100%逐流采样（化学和古地磁）的方式进行采样，同时对丰富的地壳捕虏体进行采样，对精选的更新世熔岩进行横向采样，并对两个非常不均匀的全新世流进行详细的地表采样。通过古长期磁变资料、物理地层学、地球化学和岩石学资料以及高分辨率年代学资料的整合，将这些剖面进行对比，详细重建TSP的喷发历史。

The Quaternary Southern Volcanic Zone (SVZ) of the Chilean Andes has been investigated by teams of US scientists concerned with quantifying the mantle source components in arc parent magmas, and the degree to which these magmas have interacted with arc crust. Longitudinal variations in crustal age, thickness, and the age of the subducted plate make this an ideal target for regional studies. The primary focus of this project is an exceptionally detailed and comprehensive investigation of Tatara-San Pedro (TSP) (36o S), the youngest edifice (ca. 150ka to Holocene) of the San Pedro-Pellado volcanic complex. This study will be grounded on a wealth of regional information concerning along-strike and across strike variations in Quaternary activity. In addition to its compositional variability, TSP is exceptionally well exposed from its base: 1 km vertical (or composite) sections (up to 150 flows) are exposed in deep glacial canyons from all quadrants of the cone. These sections will be sampled on a 100% flow-by-flow basis (chemistry and paleomagnetism) in conjunction with sampling of abundant crustal xenoliths, lateral sampling of select Pleistocene lavas, and detailed surface sampling of two spectacularly heterogeneous Holocene flows. A detailed reconstruction of the eruptive history of TSP will be made by correlating among these sections through integration of paleosecular magnetic variation data, physical stratigraphy, geochemistry and petrography, and high-resolution geochronology.