Zinc and germanium in the sedimentary rocks of Gale Crater on Mars indicate hydrothermal enrichment followed by diagenetic fractionation

Abstract

Zinc and germanium enrichments have been discovered in sedimentary rocks in Gale Crater, Mars, by the Alpha Particle X‐ray Spectrometer on the rover Curiosity. Concentrations of Zn (910 ± 840 ppm) and Ge (65 ± 58 ppm) are tens to hundreds of times greater than in Martian meteorites and estimates for average silicate Mars. Enrichments occur in diverse rocks including minimally to extensively altered basaltic and alkalic sedimentary rocks. The magnitude of the enrichments indicates hydrothermal fluids, but Curiosity has not discovered unambiguous hydrothermal mineral assemblages. We propose that Zn‐ and Ge‐rich hydrothermal deposits in the source region were dispersed in siliciclastic sediments during transport into the crater. Subsequent diagenetic mobilization and fractionation of Zn and Ge is evident in a Zn‐rich sandstone (Windjana; Zn ~4000 ppm, Ge ~85 ppm) and associated Cl‐rich vein (Stephen; Zn ~8000 ppm, Ge ~60 ppm), in Ge‐rich veins (Garden City; Zn ~2200 ppm, Ge ~650 ppm), and in silica‐rich alteration haloes leached of Zn (30–200 ppm). In moderately to highly altered silica‐rich rocks, Ge remained immobile relative to leached elements (Fe, Mn, Mg, and Ca), consistent with fluid interaction at pH ≪ 7. In contrast, crosscutting Ge‐rich veins at Garden City suggest aqueous mobilization as Ge‐F complexes at pH < 2.5. Multiple jarosite detections by the CheMin X‐ray diffractometer and variable Zn concentrations indicate diagenesis of lower Mount Sharp bedrock under acidic conditions. The enrichment and fractionation of Zn and Ge constrains fluid events affecting Gale sediments and can aid in unraveling fluid histories as Curiosity's traverse continues.

UV-Induced Nanoparticles-Formation, Properties and Their Potential Role in Origin of Life

“…Evidences of water alteration and hydrothermal environment have been discovered, for instance, in the case of the famous Gale Crater formed on Mars during the late heavy bombardment about 3.8 Gya, close to the time of origin of life on Earth [64]. Importantly, Zn enrichment 4000-8000 ppm in sandstone discovered in sedimentary rocks in Gale Crater, Mars, by the Alpha Particle X-ray Spectrometer on the rover, Curiosity, indicates such a fractionation connected to hydrothermal fluids [65]. However, information regarding the concentration of Cd in the Gale impact structure is missing in current literature.…”

The potential science and engineering value of samples delivered to Earth by Mars sample return

“…These include Gale Crater (Zn‐ and Ge‐enrichment measured by Curiosity rover; Berger et al. ), and two of the three finalist M‐2020 candidate landing sites: Columbia Hills (Squyres et al. ; Ruff et al.…”

Experimental and Simulation Efforts in the Astrobiological Exploration of Exooceans

“…Given the widespread existence of H 2 O, rocks, and heat in planetary bodies, hydrothermal environments are expected to be ubiquitous in the Solar System (e.g., Vance et al 2016;Neveu et al 2017). In fact, recent spacecraft explorations have found geochemical evidence for the occurrence of hydrothermal activities on Mars and Enceladus (e.g., Squyres et al 2008;Berger et al 2017;Waite et al 2017).…”

“…Given a high heat flux on early Mars and high porosity of Martian crust, a substantial amount of groundwaters would have existed within deep crust, plausibly causing water-rock interactions at high temperatures on early Mars (Michalski et al 2013). The NASA Mars Exploration Rover Spirit and the Mars Science Laboratory Rover Curiosity have found geochemical evidence for upwelling of hydrothermal fluids and Ge and Zn enrichments (Squyres et al 2008;Berger et al 2017), within sediments near their landing sites.…”