Fig. 2. Mineral endmembers.
In each panel, black spots show no diffraction and green spots show diffraction. Molar abundances in all panels. (A) Sulfate identification. High-SO3 regions are classified as MgSO4 or CaSO4. CaSO4 endmember may incorporate some FeSO4. (B) Cl-bearing endmember classification. Mixing area results from physical mixing of high-Cl phases with variable amounts of high-Na phase (feldspar). For low-Na abundances, Na correlates with Cl with Na/Cl consistent with the PIXL detection of perchlorate. (C) Various endmembers including sulfate minerals, low-(Fe,Mg)-silicate, and (Fe,Mg)-carbonate. (D) Same classification diagram as in (C) but with contributions from sulfate minerals and Fe,Cr,Ti-spinels subtracted from each spot. Unsubtracted data are shown in light gray. Removal of accessory minerals and stability of inferred secondary endmembers are shown by tightening of spots around the remaining endmembers.