Fig. 2: Compositional and textural analyzes of Ouzel_Falls by PIXL and WATSON.

WATSON image with enhanced color and 1% contrast stretch (A) and PIXL Red-Green Blue (RGB) X-Ray-Fluorescence (XRF) maps (B, C) showing the location of the green-blue Fe-phosphate minerals, and other major phases in the Ouzel_Falls abrasion patch. RGB triangles show how color mixing between elements will appear, i.e., Fe+P = yellow in (B). The approximate footprints of the PIXL scans are shown in (A–C). D Ternary diagram illustrating compositional mixing between Ouzel_Falls silicates, carbonates, and Fe-phosphates at PIXL’s resolution with ideal linear mixing trends between the major phases and an Fe-phosphate with a P/Fe ratio of ~2/3. The high-P PMCs (PIXL Motion Counters) include those with P₂O₅ > 10 wt%, SiO₂ < 30 wt%, and SO₃ < 5 wt%. Terrestrial Fe-phosphate minerals compositions compiled from ideal stoichiometry. (E, F) PIXL XRF data illustrating how high-P PMCs are correlated with high-Fe concentrations and decorrelated with Ca. A weighted orthogonal regression through the high-P points in (E) results in a P/Fe slope ratio of 0.67 ± 0.11 (SD = Standard Deviation) (P/Fe ~2/3), b = −0.14 ±0.05. All quantitative element concentrations are corrected for surface roughness and diffraction using the method outlined in ref.³⁸ (Supplementary Dataset 1).