Pristine lunar glasses: Criteria, data, and implications

Abstract

Major‐element analyses of several thousand glasses from all of the Apollo landing sites have resulted in the identification of 25 groups of pristine (i.e., volcanic) glass. The nickel in these pristine glasses is shown to be indigenous, not meteoritic contamination, and to be correlated with Mg. The chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts. The pristine glasses support the view that assimilative processes [Ringwood and Kesson, 1976] involving two cumulate systems in the differentiated mantle operated during mare petrogenesis. The reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses. Data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history. Alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses.

Phase equilibria of ultramafic compositions on Mercury and the origin of the compositional dichotomy

“…However, the low FeO magma ocean of Mercury might not have overturned because of the slightness of the density gradient within the cumulate pile (Brown and Elkins-Tanton, 2009;Riner et al, 2010). But, even without density instability, the thin (300-400 km) mantle of Mercury (Smith et al, 2012) will, for a range of structures, convect for much of (Fan), lunar magnesian-suite (MgSuite), lunar mare basalts (MB; data compiled in Papike et al, 1998), lunar ultramafic glasses (UM; Delano, 1986), surface basalts from Mars (Mars), shergottites (Sherg; data compiled by Filiberto and Dasgupta, 2011) and potential compositions of the bulk silicate fraction of Mercury (numbers refer to Supplementary Table 2). Filled symbols are data calculated on an oxide basis; white symbols are data corrected for the distribution of major elements between silicate, metal and sulfide melts.…”

Compressibility of molten Apollo 17 orange glass and implications for density crossovers in the lunar mantle

“…Uncertainties associated with using the sink/float technique stem partly from the accuracy and precision of the calibration curves used to constrain sample pressure and temperature conditions, and from the narrowness of the Table 1 Average Apollo 17 orange glass compositions, compared to black and green glass compositions (Delano, 1986 Krawczynski and Grove (2008).…”

“…Delano, 1986;Shearer et al, 2006). The picritic volcanic glasses are characterised by a broad range in titanium content, with values ranging up to 16.4 wt%.…”

Science Priorities for Mars Sample Return

“…Such samples would supply important information on the mineralogy of explosive volcanic eruptions, grain-size information critical to the interpretation of volcanic eruptions and tephra transport, and ages of explosive eruptive phases of the history of Mars. Volcanic glasses would also represent a unique opportunity to sample primitive magmas from the mantle, as demonstrated on the Moon (e.g., Delano, 1986).…”