Evidence for Multiple Diagenetic Episodes in Ancient Fluvial‐Lacustrine Sedimentary Rocks in Gale Crater, Mars

Abstract

The Curiosity rover's exploration of rocks and soils in Gale crater has provided diverse geochemical and mineralogical data sets, underscoring the complex geological history of the region. We report the crystalline, clay mineral, and amorphous phase distributions of four Gale crater rocks from an 80‐m stratigraphic interval. The mineralogy of the four samples is strongly influenced by aqueous alteration processes, including variations in water chemistries, redox, pH, and temperature. Localized hydrothermal events are evidenced by gray hematite and maturation of amorphous SiO2 to opal‐CT. Low‐temperature diagenetic events are associated with fluctuating lake levels, evaporative events, and groundwater infiltration. Among all mudstones analyzed in Gale crater, the diversity in diagenetic processes is primarily captured by the mineralogy and X‐ray amorphous chemistry of the drilled rocks. Variations indicate a transition from magnetite to hematite and an increase in matrix‐associated sulfates suggesting intensifying influence from oxic, diagenetic fluids upsection. Furthermore, diagenetic fluid pathways are shown to be strongly affected by unconformities and sedimentary transitions, as evidenced by the intensity of alteration inferred from the mineralogy of sediments sampled adjacent to stratigraphic contacts.

Constraints on the Mineralogy and Geochemistry of Vera Rubin Ridge, Gale Crater, Mars, From Mars Science Laboratory Sample Analysis at Mars Evolved Gas Analyses

“…Phyllosilicates with this d-spacing have only been observed previously in the Oudam (OU) drill sample (Achilles et al, 2020;Bristow et al, 2018). As at OU, there are three possible explanations for this observation.…”

APXS‐Derived Compositional Characteristics of Vera Rubin Ridge and Murray Formation, Gale Crater, Mars: Geochemical Implications for the Origin of the Ridge

“…The chemistry of the Murray formation below VRR is relatively uniform over a significant elevation range, in contrast to lithologies encountered within the Bradbury group (Figure 4 and Table S3) (McLennan et al, 2013;Schmidt et al, 2014;Thompson et al, 2016). This and the similar basaltic, igneous mineralogy (Achilles et al, 2020;Bristow et al, 2018;Rampe, Blake, et al, 2020) of the Murray formation below VRR (excluding the Pahrump Hills targets) indicate a similar provenance for most of the Murray sediment.…”

“…Duluth has a slightly lower abundance of phyllosilicate and less amorphous material than the Sutton Island drilled fines (Quela and Sebina; Achilles et al, 2020;. Dissolution of the Blunts Point phyllosilicate and amorphous phases and removal of Al and Si from these phases might therefore be the source for at least some of the Si and Al.…”

Hydrothermal Precipitation of Sanidine (Adularia) Having Full Al,Si Structural Disorder and Specular Hematite at Maunakea Volcano (Hawai'i) and at Gale Crater (Mars)

“…Ideal high sanidine, that is sanidine with full Al,Si structural disorder, is characterized by random distribution of Al and Si atoms at the four equivalent tetrahedral sites in a three-to-one ratio and is stable at temperatures >900°C (e.g., Parsons et al, 2015). Although only sanidine data for Windjana are plotted, Gale crater drill samples show a similar plagioclase-sanidine relationship ( Figure 5a) (Achilles et al, 2020;Morrison et al, 2018;Rampe et al, 2020). We reexamined CheMin XRD patterns for all other sanidine-bearing samples, and they contained only minor amounts of sanidine which prevented calculation of reliable Rietveld unit-cell parameters.…”

“…For all other drill samples on the plains of Gale crater through Vera Rubin ridge (VRR) on Mt. Sharp, plagioclase (~andesine) is the dominant feldspar: "John Klein," "Cumberland," "Confidence Hills," "Telegraph Peak," "Buckskin," "Marimba," "Quela," "Sebina," "Duluth," "Stoer," and "Highfield" have 3 to 9 wt.% sanidine and 38-56 wt.% plagioclase; and "Mojave2," "Big Sky," "Greenhorn," "Lubango," "Okoruso," "Oudam," and "Rock Hall" have no detectable sanidine and 38 to 55 wt.% plagioclase (Achilles et al, 2020;Bristow et al, 2018;Morrison et al, 2018;Rampe et al, 2017Rampe et al, , 2020. Treiman et al (2016) developed hypotheses for both igneous and nonigneous origins for Windjana high sanidine.…”