Hekla Revisited: Fractionation of a Magma Body at Historical Timescales
نویسندگان
چکیده
Abstract Hekla is an elongate volcano that lies at the intersection of South Iceland Seismic Zone and Eastern Volcanic Zone. We report major trace element, oxygen isotopic, H2O analyses on rocks, glass, melt inclusions, minerals from almost all historical lavas tephra deposits. This new dataset confirms remarkable observation not only are many eruptions compositionally zoned felsic to mafic, but extent zoning relates directly length repose since previous eruption. Compositional data consistent with origin basaltic andesites by fractional crystallization, no measurable crustal interaction once andesite has been produced. Although 1104 CE Plinian rhyolite 1158 dacite also created uranium–thorium isotopic disequilibria measured others require they evolved in a separate body, where magma stored molten state for >104 years. Consistent element trends ratios, as well oxygenisotopic data, preclude significant input into evolving magma. The phenocryst assemblages dominated crystals formed their host melt; exception dacite, which contains abundant melt. A suite thermobarometers indicates most lower crust temperatures ranging ∼1010 850 °C. Hekla’s unique systematic petrological time series geophysical activity attributed unusual geometry we propose be tabular, vertically macrodike, extending upper crust. vertical body recharged end each eruption, then undergoes cooling crystallization until subsequent entire system supplied lower-crustal andesite, produced reservoir thermochemically buffered Cooling background geothermal gradient shallow accounts relationship between composition.
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ژورنال
عنوان ژورنال: Journal of Petrology
سال: 2021
ISSN: ['1460-2415', '0022-3530']
DOI: https://doi.org/10.1093/petrology/egab001