Halogen Elements in Sedimentary Systems and Their Evolution During Diagenesis

Halogens in Eclogite Facies Minerals from the Western Gneiss Region, Norway

“…The Br/Cl and I/Cl ratios obtained in this study (Figure 8d) are generally consistent with the trend defined by hydration reactions in a previous study of the WGR [60]. The evolution of halogen ratios during hydration reactions also mimics the trend of seawater evaporation [60,112], whereby aH 2 O is effectively lowered, without affecting the fluid Br/Cl ratio, until increasing salinity promotes the precipitation of halite, which then drives the Br/Cl and I/Cl ratios of the residual fluid higher. This trend indicates strong fractionation of Cl and Br between minerals and fluids [60].…”

Multiphase Volatilization of Halogens at the Soil‐Atmosphere Interface on Mars

“…Constant eolian processing of the dune soil (62.5 μm-2 mm, sand-size clasts on the Wentworth scales; ISO 14688-1, 2017;Wentworth, 1922) likely overprints provenance and alteration pathways. Thus, the compositions of the active Bagnold dune soil may be inconsistent with other more stagnant Gale soils (Bridges & Ehlmann, 2018;Ehlmann et al, 2017;O'Connell-Cooper et al, 2017, 2018. Therefore, in the ensuing discussion, we separate Bagnold soils from the result of Gale samples (annotated as Gale*).…”

“…The reason for that is that fluid-related processes alone would not form natural halite containing very low Br abundance. Initial Br/Cl ratios of seawater (from which most brine on Earth originates) and partition coefficient of Br − between seawater and halite are well known, that both initial precipitations of halite and subsequent dissolution-precipitation of precipitated halite would not result in a Br as low as 5-20 mg/kg (Worden, 2018). In addition, as the brine continuously concentrates after halite precipitation, the fluid would contain higher Br − content since Br prefers to remain in the brine when halite precipitates.…”

“…Given the present cold and dry climate of Mars, briny fluids are one of the few ways by which chemical alteration can be sustained in the critical zone. Cl and Br are highly mobile in brine systems associated with soil processes, with Br commonly used to characterize terrestrial evaporation processes (e.g., Worden, 2018). Due to their possible shared provenance from volcanic outgassing and close relation in fluid systems and resultant secondary mineralogy, variations of Cl and Br in Martian soils and rocks are frequently attributed to their behavior in water‐rock systems, including evaporative sedimentation and post‐deposition fluid migration (Clark et al., 2005; Gellert et al., 2006; Knoll et al., 2008; Marion et al., 2009; Rao et al., 2009; Yen et al., 2005).…”

“…Given the present cold and dry climate of Mars, briny fluids are one of the few ways by which chemical alteration can be sustained in the critical zone. Cl and Br are highly mobile in brine systems associated with soil processes, with Br commonly used to characterize terrestrial evaporation processes (e.g., Worden, 2018). Due to their possible shared provenance from volcanic outgassing and close relation in fluid systems and resultant secondary mineralogy, variations of Cl and Br in…”