title: Determining volcanic eruption styles on Earth and Mars from crystallinity measurements.
abstract: Both Earth and Mars possess different styles of explosive basaltic volcanism. Distinguishing phreatomagmatic eruptions, driven by magma-water interaction, from 'magmatic' explosive eruptions (that is, strombolian and plinian eruptions) is important for determining the presence of near-surface water or ice at the time of volcanism. Here we show that eruption styles can be broadly identified by relative variations in groundmass or bulk crystallinity determined by X-ray diffraction. Terrestrial analogue results indicate that rapidly quenched phreatomagmatic ejecta display lower groundmass crystallinity (<35%) than slower cooling ejecta from strombolian or plinian eruptions (>40%). Numerical modelling suggests Martian plinian eruptive plumes moderate cooling, allowing 20-30% syn-eruptive crystallization, and thus reduce the distinction between eruption styles on Mars. Analysis of Mars Curiosity rover CheMin X-ray diffraction results from Gale crater indicate that the crystallinity of Martian sediment (52-54%) is similar to pyroclastic rocks from Gusev crater, Mars, and consistent with widespread distribution of basaltic strombolian or plinian volcanic ejecta.
authors.affiliation: School of the Environment, Washington State University, Webster Physical Science Building, Room 1228, Pullman, Washington 99164, USA.
authors.forename: Kellie T
authors.initials: KT
authors.lastname: Wall
authors.affiliation: School of Environment, University of Auckland, Commerce A Building, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Rowe
authors.affiliation: Institute of Geochemistry and Petrology, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Ben S
authors.initials: BS
authors.lastname: Ellis
authors.affiliation: Department of Earth Sciences, Brock University, 500 Glenridge Avenue, Saint Catharines, Ontario, Canada L2S 3A1.
authors.forename: Mariek E
authors.initials: ME
authors.lastname: Schmidt
authors.affiliation: School of Environment, University of Auckland, Commerce A Building, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Eccles