[Folda] Friday seminar - 3 March 12:30 - Stephanie Grocke "Magma Dynamics and Evolution in Continental Arcs: Insights from the Central Andes "

[Maren Kahl]

Dear all,

 

a quick reminder that our  Friday seminar series continues today (3 March) at 12:30 in the seminar room on the 3rd floor with a presentation given by:

Stephanie Grocke "Magma Dynamics and Evolution in Continental Arcs: Insights from the Central Andes"

The minor lithologies erupted from “monotonous” magmas record processes that are otherwise lost in the inexorable march to homogeneity that characterizes the long-term evolution of many large volume, caldera-forming magma systems within continental arcs. For example, the 5.65 to 1.80 Ma Cerro Guacha Caldera Complex (CGCC) in the Altiplano-Puna Volcanic Complex of SW Bolivia, with >90% of its >2500 km3 erupted volume consisting of crystal-rich dacite has all the characteristics of a “monotonous” magma system. However, it also records minor lithologic heterogeneity. Such hand-sample scale heterogeneity is ubiquitous in dominantly “monotonous” magmas, yet remains poorly investigated. We have explored the heterogeneity in the CGCC, and its implications for the construction and evolution of  “monotonous” magma systems. Integrating geochemical modeling with the volcanological framework we find that andesite magma played a large role in the development and evolution of the “monotonous” magma system. Andesitic recharge not only sustained the pre-eruption magma reservoir’s dominant dacitic composition throughout its history, but also may have acted as an eruption trigger. Our findings complement investigations that have identified heterogeneity at the crystal- and micro-scale, but emphasize that upper crustal processes are recorded as hand-sample scale heterogeneity that is serendipitously sampled by eruption before being integrated into a “monotonous” whole.

 

Maria & Maria



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