SuperCam showed that the coatings are enriched in hydrogen and sometimes magnesium. In addition, images from Mastcam-Z suggest that they also contain iron oxides. Both the hydrogen and iron oxides point to past water being involved in the formation of the coatings. That shouldn’t be too surprising, perhaps, since this area in Jezero Crater used to be a lake a few billion years ago.https://earthsky.org/space/purple-rocks-mars-perseverance-rover-desert-varnish/
The rocks resemble so-called desert varnish, which protect microbes from the sun’s radiation. It’d be interesting to find out whether cyanobacteria that once existed on Mars did this…but the four billion year old question is, how did those bacteria get there in the first place?