The Petrochemistry of Jake_M: A Martian Mugearite

Abstract

Jake_M, the first rock analyzed by the APXS instrument on the Curiosity rover, differs significantly in chemical composition from other known martian igneous rocks: It is alkaline (>15% normative nepheline) and relatively fractionated. Jake_M is similar compositionally to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. By analogy with these comparable terrestrial rocks, Jake_M could have been produced by extensive fractional crystallization of a primary alkaline or transitional magma at elevated pressure, with or without elevated water contents. The discovery of Jake_M suggests that alkaline magmas may be more abundant on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (e.g., phonolites and trachytes). Introduction:

Melting of the primitive martian mantle at 0.5–2.2 GPa and the origin of basalts and alkaline rocks on Mars

“…In early 2013, with the first results obtained at Gale crater by Curiosity (Stolper et al, 2013) and the description of a new meteorite type -the regolith breccias 7034/7533 (see next section) -alkaline magmatism was shown to be ubiquitous on Mars and of greater importance than previously thought (McSween et al, 2009). Numerous rocks analyzed at Gale crater displayed extreme contents of alkali elements, particularly potassium.…”

“…The TiO 2 content (2.3 wt.%) is out of the field. The compositions of other martian rocks are from Agee et al (2013), Humayun et al (2013), McSween et al (2006b, Ming et al (2008) and Stolper et al (2013). a magma ocean (Debaille et al, 2009;Elkins-Tanton et al, 2005;Scheinberg et al, 2014).…”

“…Further studies of the infrared spectral data (Carter and Poulet, 2013;Christensen et al, 2005;Wray et al, 2013), new meteorite discoveries (Agee et al, 2013;Humayun et al, 2013), recent analyses by the Mars Science Laboratory mission (Stolper et al, 2013;Sautter et al, 2014), and re-interpretation of Pathfinder analyses (Foley et al, 2003) have also highlighted the presence of alkaline rocks, silicic rocks, and anorthosites. These occurrences indicate that the martian crust exhibits a larger compositional vari-ability than initially thought.…”

ChemCam activities and discoveries during the nominal mission of the Mars Science Laboratory in Gale crater, Mars

“…39,40,49,50 Igneous rocks observed to the west of the Yellowknife Bay (YKB) sedimentary formation are oat rocks or clasts in conglomerates. ChemCam textural and compositional analyses led to the identication of 53 massive (non-layered) igneous targets, 39,40 both intrusive and effusive, with mac or felsic samples, the latter dominated by feldspar minerals.…”

Determining volcanic eruption styles on Earth and Mars from crystallinity measurements

“…Sharp 14 . To date, Curiosity has encountered mainly volcaniclastic and isochemically altered basaltic sediments along its traverse to Yellowknife Bay 15 . Given the high likelihood that Curiosity will continue to encounter volcanically derived deposits, we present here a novel methodology to distinguish between types of mafic explosive eruptions on rocky planets (for example, plinian, strombolian and phreatomagmatic).…”