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The temporal record of magmatism at Cerro Uturuncu, Bolivian Altiplano

Research output: Chapter in Book/Report/Conference proceedingChapter in a book

Original languageEnglish
Title of host publicationGeological Society Special Publication
Publisher or commissioning bodyGeological Society of London
Pages57-83
Number of pages27
Volume422
Edition1
DOIs
StatePublished - 2015

Publication series

NameGeological Society Special Publication
Number1
Volume422
ISSN (Print)03058719

Abstract

Twenty-six new 40Ar/39Ar plateau ages for 23 lavas and domes from the Uturuncu volcano in the Altiplano of SW Bolivia reveal a protracted eruptive history from 1050±5 to 250±5 ka. Eruptions have been exclusively effusive, producing some 50 km3 of high-K dacites and silicic andesites. Bimodal mineral compositions, complex mineral textures, the presence of andesitic magmatic enclaves within dacites and linear chemical trends on binary element plots all indicate that magma mixing is an important petrogenetic process at Uturuncu. Post-458 ka, distinct high and low MgO-Cr magmas are resolved. These magmas erupt during similar times, suggesting that eruptions are tapping different parts of the magma system, albeit from the same vent system. Volcanic and petrological features are consistent with the existence of a vertically extensive magma mush column beneath Uturuncu, and calculated buoyancy forces are sufficient to drive effusive eruptions. Eruptive activity is episodic, with six eruptive periods separated by hiatuses of >50 kyr. Cumulative volume curves demonstrate that the majority of the edifice formed between 595 and 505 ka. The episodicity of eruptions is most likely to be related to fluctuations in the magma supply to the underlying Altiplano-Puno Magma Body.

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