Date of Graduation
Spring 2020
Degree
Master of Science in Geospatial Sciences
Department
Geography, Geology, and Planning
Committee Chair
Gary Michelfelder
Abstract
The Central Andes in South America contain many active volcanoes and volcano complexes due to constant subduction producing extrusive rocks varying in composition. The Lazufre Complex, Chile-Argentina border, consists of two Pleistocene volcanic centers, Lastarria and Cordon del Azufre andesite and dacite lava flows and domes. Whole-rock K-Ar dates of lavas from Cordon del Azufre place the most recent eruptions at 0.6-0.3 Ma ±0.3 Ma. Major-element data of plagioclase and pyroxene show homogeneous compositions between the centers, which is consistent with whole rock major- and trace-element compositions. The primary composition of the pyroxenes are augite and diopsides for cpx and hypersphene for opx and the primary composition of the plagioclases are An35-78. The Fe-Ti oxide thermo-oxybarometric, feldspar-liquid thermobarometirc, and cpx and cpx-liquid thermobarometric models were used. Temperatures and pressure calculations of both centers range from 970-1070°C and 60-700 MPa, respectively. Detailed investigation of plagioclase textures provide evidence for magma mixing and fractional crystallization as major pre-eruptive processes. Distinct magma storage zones are suggested, with a deeper zone at mid crustal levels (>20 km depth), a second zone at shallow-crustal levels (10-15 km depth).
Keywords
Lazufre, geochemistry, geothermobarometry, magma plumbing system, andesite, Andes Mountains, Cordon del Azufre, Lastarria
Subject Categories
Geochemistry | Geology | Volcanology
Copyright
© Brooke Erin Benz
Recommended Citation
Benz, Brooke Erin, "Geochemistry of the Lazufre Volcanic Complex: Determining the Geometries and Processes of the Magmatic Sources in the Central Andean Volcanic Zone" (2020). MSU Graduate Theses. 3501.
https://bearworks.missouristate.edu/theses/3501
