Mafic enclaves record syn-eruptive basalt intrusion and mixing

Plail, Melissa and Edmonds, Marie and Woods, Andrew W. and Barclay, Jenni and Humphreys, Madeleine C.S. and Herd, Richard A. and Christopher, Thomas (2018) Mafic enclaves record syn-eruptive basalt intrusion and mixing. Earth and Planetary Science Letters, 484. pp. 30-40. ISSN 0012 821X DOI https://doi.org/10.1016/j.epsl.2017.11.033

[img] Text
1-s2.0-S0012821X17306696-main.pdf

Download (1MB)
Official URL: https://doi.org/10.1016/j.epsl.2017.11.033

Abstract

Mafic enclaves hosted by andesite erupted at the Soufrière Hills Volcano between 1995 and 2010 yield insights into syn-eruptive mafic underplating of an andesite magma reservoir, magma mixing and its role in sustaining eruptions that may be widely applicable in volcanic arc settings. The mafic enclaves range in composition from basalt to andesite and are generated from a hybrid thermal boundary layer at the interface between the two magmas, where the basalt quenches against the cooler andesite, and the two magmas mix. We show, using an analytical model, that the enclaves are generated when the hybrid layer, just a few tens of centimetres thick, becomes buoyant and forms plumes which rise up into the andesite. Mafic enclave geochemistry suggests that vapour-saturated basalt was underplated quasi-continuously throughout the first three eruptive phases of the eruption (the end member basalt became more Mg and V-rich over time). The andesite erupted during the final phases of the eruption contained more abundant and larger enclaves, and the enclaves were more extensively hybridised with the andesite, suggesting that at some time during the final few years of the eruption, the intrusion of mafic magma at depth ceased, allowing the hybrid layer to reach a greater thickness, generating larger mafic enclaves. The temporal trends in mafic enclave composition and abundance suggests that basalt recharge and underplating sustained the eruption by the transfer of heat and volatiles across the interface and when the recharge ceased, the eruption waned. Our study has important implications for the petrological monitoring of long-lived arc eruptions.

Item Type: Article
Uncontrolled Keywords: 2017AREP; IA72
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 484
Page Range: pp. 30-40
Identification Number: https://doi.org/10.1016/j.epsl.2017.11.033
Depositing User: Sarah Humbert
Date Deposited: 10 Apr 2019 13:41
Last Modified: 10 Apr 2019 13:41
URI: http://eprints.esc.cam.ac.uk/id/eprint/4460

Actions (login required)

View Item View Item

About cookies