Autobrecciation and fusing of mafic magma preceding explosive eruptions
نویسندگان
چکیده
Abstract Bubble and crystal textures evolve during magma ascent, altering properties that control ascent such as permeability viscosity. Eruption style results from feedbacks between bubble nucleation growth, microlite crystallization, gas loss, all processes recorded in pyroclasts. We show pyroclasts of the mafic Curacautín ignimbrite Llaima volcano, Chile, record a history repeated autobrecciation, fusing, crystallization. identified with domains heterogeneous vesicle sharp contact one another are overprinted by extensive Broken crystals long axes (l) >10 μm fragmentation events eruption. A second population unbroken microlites l ≤10 overprint sutures fused domains, suggesting highly crystalline groundmass formed at shallow depths after autobrecciation fusing. Nearly contain plutonic ancestral lithics inclusions, implying fusing occurs few kilometers depth to surface. propose autobrecciated proto-pyroclasts remained melt rich enough fuse together. Lithics conduit margins were entrained into before Autobrecciation broke existing phenocrysts microlites; rapid post-fusing crystallization then generated groundmass. This proposed process has implications for interpreting products explosive eruptions.
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a Geological Sciences Department, Brown University, 324 Brook Street, Box 1846, Providence, RI 02912, USA b Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, N.W., Washington, DC 20015, USA c The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA d Environmental Science Department, Lancaster Univers...
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ژورنال
عنوان ژورنال: Geology
سال: 2022
ISSN: ['0091-7613', '1943-2682']
DOI: https://doi.org/10.1130/g50180.1