Mineralogy, provenance, and diagenesis of a potassic basaltic sandstone on Mars: CheMin X‐ray diffraction of the Windjana sample (Kimberley area, Gale Crater)

Abstract

The Windjana drill sample, a sandstone of the Dillinger member (Kimberley formation, Gale Crater, Mars), was analyzed by CheMin X‐ray diffraction (XRD) in the MSL Curiosity rover. From Rietveld refinements of its XRD pattern, Windjana contains the following: sanidine (21% weight, ~Or95); augite (20%); magnetite (12%); pigeonite; olivine; plagioclase; amorphous and smectitic material (~25%); and percent levels of others including ilmenite, fluorapatite, and bassanite. From mass balance on the Alpha Proton X‐ray Spectrometer (APXS) chemical analysis, the amorphous material is Fe rich with nearly no other cations—like ferrihydrite. The Windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite. From ChemCam Laser‐Induced Breakdown Spectrometer (LIBS) chemical analyses, Windjana is representative of the Dillinger and Mount Remarkable members of the Kimberley formation. LIBS data suggest that the Kimberley sediments include at least three chemical components. The most K‐rich targets have 5.6% K2O, ~1.8 times that of Windjana, implying a sediment component with >40% sanidine, e.g., a trachyte. A second component is rich in mafic minerals, with little feldspar (like a shergottite). A third component is richer in plagioclase and in Na2O, and is likely to be basaltic. The K‐rich sediment component is consistent with APXS and ChemCam observations of K‐rich rocks elsewhere in Gale Crater. The source of this sediment component was likely volcanic. The presence of sediment from many igneous sources, in concert with Curiosity's identifications of other igneous materials (e.g., mugearite), implies that the northern rim of Gale Crater exposes a diverse igneous complex, at least as diverse as that found in similar‐age terranes on Earth.

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

“…As mentioned previously, the region is especially enriched in potassium, 73 reecting the substantial fraction of K-feldspar (20 wt%) detected by the CheMin instrument. 94 Relatively abundant uorine detections were made, 37 and the apparent fracture-lling material was found to contain high concentrations (>10 wt%) of manganese-oxide minerals. 87 Zn enrichment turns out to be independent of the textures of the rocks detected in that stratigraphic member, from ne-and coarse-grained sandstones to pebbly conglomerates and resistant ns.…”

Large sulfur isotope fractionations in Martian sediments at Gale crater

“…These fluids could also be responsible for the sulfur-rich nature of the amorphous component of the cement. The Ca-sulfates are likely present in WJ as a result of the late-stage diagenetic processes that have resulted in Ca-sulfate veins observed near WJ (and generally present throughout the rover's traverse), although these veins were not specifically observed within the WJ drill hole 39 .…”

“…The magnetite, amorphous material, and phyllosilicates are likely cementing agents in the WJ sandstone, formed as a result of interactions with diagenetic fluids. WJ also contains trace pyrrhotite and trace Ca-sulfates (bassanite, anhydrite) 39 . The trace pyrrhotite could have precipitated from or been altered by the cementing fluids described above, which likely contained an isotopically enriched sulfur component.…”

“…The WJ sample comprises a potassium-rich basaltic mineralogy with a large amount of the Kfeldspar sanidine (~21 wt.%), as well as several secondary minerals including 2:1 phyllosilicates (~10 wt %, probably collapsed smectite clay minerals), abundant magnetite (~12 wt.%) and ~15% Fe-rich amorphous material that is also high in Cl and SO 3 (perhaps present in poorly ordered sulfate phases and/or adsorbed sulfur) 39 . The magnetite, amorphous material, and phyllosilicates are likely cementing agents in the WJ sandstone, formed as a result of interactions with diagenetic fluids.…”

Low HesperianPCO2constrained from in situ mineralogical analysis at Gale Crater, Mars

“…Sharp), the MSL team documented a ∼70 m sedimentary section of mudstones, siltstones, sandstones, and conglomerates deposited by lakes and rivers on the floor of Gale crater between 3.8 and 3.1 Ga (8). Sedimentary rocks analyzed by the CheMin X-ray diffraction (XRD) instrument during the traverse share many of the same components including (i) crystalline silicates including pigeonite, intermediate calcic plagioclase, and olivine from a basaltic source or sources; (ii) poorly crystalline clay minerals; (iii) various Fe oxides including magnetite; (iv) Ca-sulfate minerals, which mainly occur in cross-cutting fractures and veins; and (v) an X-ray amorphous component (9,10). Thus far, carbonate minerals have not been definitively detected in Gale Crater sedimentary rocks.…”