B35: Evaluating the Evolution of Magmatic Systems on Earth: Insights from Volcanoes and their Minerals on the Bolivian Altiplano, South America

Partial melting of Earth’s mantle in various tectonic settings leads to a wide array of magmatic processes and products in both at-plate boundary and intraplate settings. Of these, the volcanic products in regions where oceanic plates are descending below (or subducting beneath) overriding continental plates are mineralogically and chemically the most diverse. Classic examples include the Cascade Mountain Range of the western USA and the Andes of South America. The magmatism expressed at the surface (e.g. Mount St Helens, Washington, and Volcan Uturuncu, Bolivia) is the result of a complex interplay between dehydration of the down going oceanic plate, +/- sediment melting, partial melting of the mantle, +/- incorporation of components within the overriding continental plate. In order to advance scientific understanding of the processes occurring in these complex systems, study of the systems’ components is necessary. This study will focus on the volcanic products erupted from a volcano (Quillacas) on the Bolivian Altiplano associated with volcanism occurring in the Andes. Particularly, the lavas from Quillacas are of interest because they contain pieces of 1) the underlying continental plate and 2) the magmatic system through which the lavas travelled on route to the surface (xenoliths and hornblendites respectively). Specifically, minerals of the same type that exist within the lavas, xenoliths, and cumulates can be investigated in order to evaluate the extent of interaction between the different components at depth, i.e. did the minerals transfer between the different components of the magmatic system? A PhD student in the Department of Geology is investigating the hornblendites and xenoliths. I will study minerals which are present in both the lavas and the hornblendites, and compare them both texturally and chemically. I will focus on the characteristics of 2 minerals: hornblende and apatite. I will use in-house facilities available in the Department of Geology and Environmental Earth Science (polarized light microscopy, PLM) and the Center for Advanced Microscopy and Imaging (scanning electron microscopy, SEM) to characterize textures (size and shape). I will use Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to acquire their chemical compositions in-situ on each grain. I plan to do this in house at Miami due to the arrival of this type of instrumentation in Spring of 2020. Textural and chemical differences and/or similarities between the hornblende and apatite

Author: Raghad Al Gbory

Faculty Advisor: Dr. Claire McLeod, Department of Geology and Environmental Earth Sciences

Graduate Student Advisor: Liannie Velazquez Santana, Department of Geology and Environmental Sciences

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