Date of Graduation

Summer 2023


Master of Natural and Applied Science in Geography, Geology, and Planning


Geography, Geology, and Planning

Committee Chair

Gary Michelfelder


Between 12-25°S latitude there is prolific volcanism fueled by the Altiplano-Puna Magmatic Body (APMB), a mid-crustal magma body above the 30° angle subduction of the Nazca plate and within 60-70 km thick South American crust. Cerro Uturuncu, a stratovolcano constructed above the center of the APMB, can provide insight to the evolution of the APMB over time. Previous research suggests that the APMB is more homogenous near its center as opposed to its edges. However, the processes that led to greater homogenization as well as the structure of the magma body below Cerro Uturuncu remain unknown. This research contributes greater understanding to the homogenization of and mixing within the APMB and comments on how this relates to magma architecture and residence times. While previous research on Cerro Uturuncu has focused on whole- rock geochemistry, this research evaluates sub-crystal plagioclase geochemistry and geochronometry. Textural classification, major and trace element analysis, and Sr diffusion modeling were performed on eight Cerro Uturuncu samples representing the four largest lava stages in recent Cerro Uturuncu history (1 Ma) using optical microscopy, LA-ICP-MS, EPMA, and Lubbers et al. (2022) trace element diffusion across plagioclase python script. Overall, in the past 1 Ma, the APMB magma chamber architecture below Cerro Uturuncu condensed while the magma itself became increasingly homogenous through convection mixing events. The magma was stored at or above plagioclase closure temperatures for under 1000 years prior to eruption for the youngest two of Cerro Uturuncu’s lava stages.


Cerro Uturuncu, magma storage, magma plumbing system architecture, plagioclase, geochemistry, diffusion modeling, Central Andes, Bolivia

Subject Categories

Geochemistry | Geology | Volcanology


© Sarah Jane Rasor

Open Access