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

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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.