Small melt inclusions can record bulk magma compositions: A planetary example from the Martian basalt (shergottite) Tissint

Abstract

Melt inclusions in igneous minerals can provide constraints on magma compositions, especially for planetary samples where mass is severely limited. Small inclusions (<15 lm diameter) are more abundant than large ones, but have been used little from concern that they did not entrap average magma, but are rich in melt of a diffusional layer against the host mineral. We compared bulk compositions and calculated original compositions of small and large melt inclusions in the Martian basalt meteorite (shergottite) Tissint. Small and large melt inclusions are consistent with the same line of igneous differentiation, have the same abundance ratios for incompatible elements (P, Ti, Al, K, Na), and are consistent with derivation from the bulk composition of Tissint (inferred to represent its parent melt composition). For Tissint, then, small melt inclusions show no evidence of entrapping diffusional boundary layers, and appear to have entrapped bulk magma. Thus, its small inclusions can be as useful as larger ones; this may be so for other planetary samples, and thus provides an additional tool for investigating planetary magmas.

The history of the Tissint meteorite, from its crystallization on Mars to its exposure in space: New geochemical, isotopic, and cosmogenic nuclide data

“…b), as well as Ni‐bearing Fe‐sulfides and oxides (chromites). Similar observations were reported by Sonzogni and Treiman (). Pyroxenes occur as euhedral to subhedral grains, up to about 1 mm in length.…”

Martian meteorite Tissint records unique petrogenesis among the depleted shergottites

“…It is noteworthy that the melt inclusions of Tissint represent true melt composition of the Martian mantle (Peters et al. ; Sonzogni and Treiman ; Basu Sarbadhikari et al. ).…”

Controlled Cooling‐Rate Experiments on Olivine‐Hosted Melt Inclusions: Chemical Diffusion and Quantification of Eruptive Cooling Rates on Hawaii and Mars

“…These reconstructed melt compositions correspond to addition of 30–45% olivine by volume back into the inclusions to achieve equilibrium with the enclosing olivine, consistent with the 30–40% by volume addition estimated for reconstructions of Y984059 melt inclusion compositions from Peters et al () using Petrolog3 (Danyushevsky & Plechov, ). Reconstruction of small glassy melt inclusions in Tissint by Sonzogni and Treiman () similarly required 25–51% olivine addition by mass to the glasses in order to achieve equilibrium with the host olivine (Fo 58 –Fo 72 ). This calculated amount of olivine extraction necessary to reconstruct compositions of shergottite melt inclusions is also consistent with the measured thickness of the narrow Fe‐rich olivine zone adjacent to the inclusion walls (i.e., 4 μm of inward olivine growth on the wall of a spherical 20 μm radius inclusion represents a 49% change in volume).…”