School of the Environment, Washington State University, Webster Physical Science Building, Room 1228, Pullman, Washington 99164, USA.
School of Environment, University of Auckland, Commerce A Building, Private Bag 92019, Auckland 1142, New Zealand.
Nat Commun. 2014 Oct 3;5:5090. doi: 10.1038/ncomms6090.
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.
地球和火星都具有不同风格的爆发玄武岩火山作用。区分由岩浆-水相互作用驱动的水成碎屑喷发与“岩浆”爆发性喷发（即斯特龙博利型和普林尼型喷发）对于确定火山作用时近地表是否存在水或冰很重要。在这里，我们表明可以通过 X 射线衍射确定的基质或整体结晶度的相对变化来广泛识别喷发样式。地球模拟结果表明，快速淬火的水成碎屑喷发喷出物的基质结晶度较低（<35%），而斯特龙博利型或普林尼型喷发的较慢冷却喷出物的基质结晶度较高（>40%）。数值模拟表明，火星普林尼喷发的喷发羽流减缓了冷却速度，允许 20-30%的同喷发期结晶，从而减少了火星上火山喷发样式之间的区别。对好奇号火星车 CheMin X 射线衍射在盖尔陨石坑采集的数据进行分析表明，火星沉积物（52-54%）的结晶度与来自火星古塞夫陨石坑的火山碎屑岩相似，这与广泛分布的玄武岩斯特龙博利型或普林尼型火山喷发喷出物一致。
