31 D4. Mineralogy, Geochemistry, Petrology, and Volcanology (Posters)

Friday, 8 April 2022
8:00 AM - 12:00 PM
Junior Ballroom B

GEOCHEMICAL COMPARISON OF THE CHASCA ORKHO SERIES AND MAGMATIC INCLUSIONS AT VOLCÁN OLLAGÜE, CENTRAL VOLCANIC ZONE, NORTHERN CHILE

Paper number: 31-8
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The Andean Central Volcanic Zone (CVZ) is a region of active volcanic and tectonic activity, in part due to the voluminous Altiplano-Puna Magma Body (APMB) underneath the modern arc front. This magma body influences a significant degree of modern-day and Holocene volcanism within the region, including our research site, Volcán Ollagüe, located in the northern portion of the APMB. However, the influences of differing sources of magma as well as the degree of different magmatic processes remain understudied. The aim of this study is to provide a greater understanding of the magmatic processes that Volcán Ollagüe experienced and how influential certain processes must have been during Ollagüe's main period of eruptive activity. This will be done by examining both the lava flows and magmatic inclusions of the 340 - 507 ka Chasca Orkho series. Therefore, our samples will be analyzed for major and minor elements using an electron microprobe, trace and rare-earth elements using laser ablation-ICPMS techniques, strontium isotope ratios and oxygen isotope values using microdrill and laser fluorination techniques, respectively. Initial observation of Chasca Orkho lavas and its magmatic inclusions show general trends of disequilibrium in the cores and rims of plagioclase phenocrysts in magmatic inclusions and main sequence lavas, respectively. Initial analysis of trace elements shows that both the Chasca Orkho lavas and its inclusions have largely similar signatures of elements La through Eu before showing notable variations in elements Gd through Lu. Additionally, plagioclase in the Chasca Orkho lavas generally experience fractionation within the crystal rims, while magmatic inclusions show more fractionation throughout plagioclase crystals overall. From these preliminary interpretations we determine that both the Chasca Orkho lava series and its inclusions have come from relatively similar magmatic sources but have undergone differing processes such as magmatic fractionation and mixing.

Geological Society of America Abstracts with Programs. Vol. 54, No. 4

doi: 10.1130/abs/2022NC-375438

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