Fluorine observations by ChemCam: A tracer of magmatic and hydrothermal processes in the martian crust

The ChemCam LIBS instrument on the Curiosity rover has observed fluorine in more than 60 locations along the traverse. These are the first fluorine detections on Mars, although the SNC meteorites contain moderate amounts of F, suggesting that is present in the Mars crust. The detection limit is < 0.4 wt % but requires the simultaneous presence of Ca in the LIBS plasma (Gaft et al., 2014). Approximately one fourth of the observations were made on conglomerate clasts in the Bradbury Rise area near the landing site, and another third were made in sediments in the Kimberley area (around sol 550). In these targets F was correlated with K, Al, and Si enrichments; in the Kimberley area they were also correlated with Li enrichments in the 10s of ppm. The most likely mineral host in these settings is muscovite and potentially also biotite.

In other observations the fluorine is correlated with high Ca; P was observed above the relatively high LIBS detection limit in some targets, suggesting the presence of fluorapatites. Chlorine was not found in association with fluorine. A number of these observations were made in the rocks around the aeolian drift (around sol 60). The presence of the implied apatites and mica minerals has strong implications for the petrologic environment in which these phases were formed. We will discuss the origin and possible processes that led to the presence of these fluorine-bearing targets.