Pyroclastic Activity at Home Plate in Gusev Crater, Mars

Abstract

Home Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic origin over an impact origin. The lower unit likely represents accumulation of pyroclastic materials, whereas the upper unit may represent eolian reworking of the same pyroclastic materials.

Determining volcanic eruption styles on Earth and Mars from crystallinity measurements

“…an understanding that the source of the amorphous component is debatable, based on the methodology developed here and the similarity in crystallinity and mineralogy between the Rocknest sand shadow sediment and the basaltic pyroclastic rocks of Gusev crater, we suggest that X-ray results are consistent with a relatively high proportion of basaltic glass indicating potentially widely distributed strombolian or plinian volcanic eruptive material on the surface of Mars 30,33 . This interpretation is consistent with the greater anticipated dispersal of explosive volcanic deposits on Mars 1 and prior observations regarding the widespread similarity between Martian soil and sediment 33 .…”

“…In contrast, Mössbauer spectroscopy results indicate a high proportion (27-29%) of npOx (absent from the Mini-TES results), suggesting that npOx may appear spectrally similar to basaltic glass using Mini-TES 30 . However, from the assumption that amorphous npOx is primarily derived from basaltic glass, the proportion of npOx may provide a means of estimating primary glass content even in severely altered volcanic rocks.…”

“…However, from the assumption that amorphous npOx is primarily derived from basaltic glass, the proportion of npOx may provide a means of estimating primary glass content even in severely altered volcanic rocks. A C wr of 55-80% from Mini-TES analysis of pyroclastic rocks in Gusev crater is consistent with a strombolian or plinian 'magmatic' eruption style, based on our methodology, rather than water/ice-driven phreatomagmatism 30,34 . However, high proportions of secondary silicate phases (up to B25%) identified in some of the Home Plate mini-TES results may imply severe alteration and an underestimation of the glass content.…”

“…The cooling rate of small (o1 cm) erupted particles therefore is controlled by the cooling rate of the eruption plume they are in equilibrium with. Numerical simulations of a near-vent gas thrust model transitioning to a convective plume 27,28 modified for Martian atmospheric pressure and temperature 29 , eruption velocities and vent diameters 1 , and magma composition 30 (Supplementary Table 1) are coupled with cooling ratecrystallization rate relationships above an estimated glass transition temperature of B730°C (refs. 18,31) to reconstruct syn-eruptive groundmass crystallization during plinian eruptions on Mars (see Supplementary Discussion 1 for details of numerical modelling).…”

Lassen Volcanic Fumaroles and Hot Springs: Analog for Mars

“…Deposits in outcrops and soils in Gusev's Columbia Hills are interpreted as hydrothermal because of elevated silica and Ti (likely a sinter or leached deposit) and high S, Cl, and Br concentrations often associated with hydrothermal fluids (Squyres et al, 2007;Schmidt et al, 2008;Yen et al, 2008). The presence of Fe-sulfate minerals and partitioning between Cl and S suggest saline-acidic hydrothermal fluids (Squyres et al, 2007(Squyres et al, , 2008, potentially fumaroles (Squyres et al, 2007;Schmidt et al, 2009) or warm liquids (Squyres et al, 2008). Water-rock interaction explains the transport of non-volatile elements (e.g.…”