B.A. Wing^a,b,c, J. Farquhar^c
aDepartment of Earth and Planetary Sciences, McGill University, Montreal QC H3A 2A7 CANADA
^bGEOTOP Research Center, C.P. 8888, Succursale Centre-ville, Montréal, QC H3C 3P8, CANADA
^cEarth System Science Interdisciplinary Center and Department of Geology, University of Maryland, College Park MD 20742 USA

We present a new set of high precision measurements of relative ³³S/³²S, ³⁴S/³²S, and ³⁶S/³²S values in lunar mare basalts. The measurements are referenced to the Vienna-Canyon Diablo Troilite (V-CDT) scale, on which the international reference material, IAEA-S-1, is characterized by δ³³S = -0.061 ‰, δ³⁴S ≡ -0.3 ‰ and δ36S = -1.27 ‰. The present dataset confirms that lunar mare basalts are characterized by a remarkable degree of sulfur isotopic homogeneity, with most new and published SF6-based sulfur isotope measurements consistent with a single mass-dependent mean isotopic composition of δ³⁴S = 0.58 ± 0.05 ‰, Δ³³S = 0.008 ± 0.006 ‰, and Δ³⁶S = 0.2 ± 0.2 ‰, relative to V-CDT, where the uncertainties are quoted as 99% confidence intervals on the mean. This homogeneity allows identification of a single sample (12022, 281) with an apparent ³³S enrichment, possibly reflecting cosmic-ray-induced spallation reactions. It also reveals that some mare basalts have slightly lower δ³⁴S values than the population mean, which is consistent with sulfur loss from a reduced basaltic melt prior to eruption at the lunar surface. Both the sulfur isotope homogeneity of the lunar mare basalts and the predicted sensitivity of sulfur isotopes to vaporization-driven fractionation suggest that less than ≈1-10% of lunar sulfur was lost after a potential moon-forming impact event.

Reference
Wing BA, Farquhar J (2015) Sulfur isotope homogeneity of lunar mare basalts. Geochimica et Cosmochimica Acta (in Press)
Link to Article [ http://www.sciencedirect.com/science/article/pii/S0016703715005323]
Copyright Elsevier