Zolenskyite, FeCr2S4, a new sulfide mineral from the Indarch meteorite

Abstract

Abstract Zolenskyite (IMA 2020-070), FeCr2S4, is a new sulfide mineral that occurs within troilite, with clinoenstatite and tridymite, in the matrix of the Indarch meteorite, an EH4 enstatite chondrite. The mean chemical composition of zolenskyite determined by electron probe microanalysis, is (wt%) S 43.85, Cr 35.53, Fe 18.94, Mn 0.68, Ca 0.13, total 99.13, yielding an empirical formula of Fe0.99Mn0.04Ca0.01Cr1.99S3.98. The ideal formula is FeCr2S4. Electron backscatter diffraction shows that zolenskyite has the C2/m CrNb2Se4-Cr3S4-type structure of synthetic FeCr2S4, which has a = 12.84(1) Å, b = 3.44(1) Å, c = 5.94(1) Å, β = 117(1)°, V = 234(6) Å3, and Z = 2. The calculated density using the measured composition is 4.09 g/cm3. Zolenskyite is a monoclinic polymorph of daubréelite. It may be a high-pressure phase, formed from daubréelite at high pressures (several gigapascals) and moderate temperatures in highly shocked regions of the EH parent asteroid before becoming incorporated into Indarch via impact mixing. Zolenskyite survived moderate annealing of the Indarch whole-rock. The new mineral is named in honor of Michael E. Zolensky, an esteemed cosmochemist and mineralo-gist at NASA’s Johnson Space Center, for his contributions to research on extraterrestrial materials, including enstatite chondrites.