How long was Meridiani Planum wet? Applying a jarosite stopwatch to determine the duration of aqueous diagenesis

Madden, M. E. Elwood; Madden, Andrew S.; Rimstidt, J. Donald

doi:10.1130/g25639a.1

Cited by 45 publications

(35 citation statements)

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“…The acidic conditions required to produce jarosite can be local and/or short‐lived, and can post date the formation of the rest of the mineral assemblage. In addition, the apparent short lifetime of jarosite in Olduvai samples is promoted by the abundance of water and warm conditions, which allow fast reequilibration of the system [ Elwood Madden et al , 2009]. However, in the very dry and cold Martian climate, it is possible that jarosite would last much longer.…”

Section: Discussionmentioning

confidence: 99%

“…Under these conditions, jarosite needs not have formed as part of an equilibrium assemblage with the other minerals observed, and could reflect different diagenetic conditions. Regardless of when it was formed, the rate at which jarosite dissolves in contact with aqueous fluids limits the amount of time a jarosite‐bearing deposit could have been exposed to such conditions since formation [e.g., Elwood Madden et al , 2009]. Elwood Madden et al 's [2009] experiments suggest that, depending on the temperature and fluid composition, a 10 μ m particle of jarosite can last from 1.5 years (in warm, dilute water) to 1 Ma (in cold, NaCl brines).…”

Section: Introductionmentioning

confidence: 99%

“…Regardless of when it was formed, the rate at which jarosite dissolves in contact with aqueous fluids limits the amount of time a jarosite‐bearing deposit could have been exposed to such conditions since formation [e.g., Elwood Madden et al , 2009]. Elwood Madden et al 's [2009] experiments suggest that, depending on the temperature and fluid composition, a 10 μ m particle of jarosite can last from 1.5 years (in warm, dilute water) to 1 Ma (in cold, NaCl brines). Concretionary jarosite is more resistant to weathering; Miocene‐aged concretionary jarosite has been observed in the Rio Tinto area of Spain [ Fairén et al , 2009].…”

Section: Introductionmentioning

confidence: 99%

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Jarosite in a Pleistocene East African saline-alkaline paleolacustrine deposit: Implications for Mars aqueous geochemistry

McHenry

Chevrier²,

Schröder

2011

J. Geophys. Res.

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[1] Jarosite occurs within altered tephra from the saline-alkaline paleolake deposits of Pliocene-Pleistocene Olduvai Gorge, Tanzania. Zeolites (mainly phillipsite), authigenic K-feldspar, and Mg/Fe-smectites dominate the mineral assemblage, indicating salinealkaline diagenetic conditions (pH > 9). As jarosite is ordinarily an indicator of acidic conditions on Earth and Mars, its association with such undisputed high-pH indicators is unexpected. Of 55 altered tephra samples collected from the paleolake basin and margin deposits, eleven contained jarosite detectable by X-ray Diffraction (XRD) (>0.15%). Mössbauer spectroscopy, Fourier Transform Infrared Reflectance (FTIR), Electron Probe Microanalysis (EPMA), X-ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) analyses confirm the presence and nature of the jarosite. This paper documents this occurrence and presents mechanisms that could produce this unusual and contradictory mineral assemblage. We favor a mechanism by which jarosite formed recently, perhaps as modern ground and meteoric water interacted with and oxidized paleolacustrine pyrite, providing local and temporary acidic conditions. However, local groundwater (at modern springs) has a pH > 9. In recent studies of Mars, the presence of jarosite or other Fe or Mg sulfates is often used to indicate dominantly acidic conditions. Regardless, the current study shows that jarosite can form in sediments dominated by alkaline minerals and solutions. Its coexistence with Mg/Fe smectites in particular makes it relevant to recent observations of Martian paleolakes.Citation: McHenry, L. J., V. Chevrier, and C. Schröder (2011), Jarosite in a Pleistocene East African saline-alkaline paleolacustrine deposit: Implications for Mars aqueous geochemistry,

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Jarosite in a Pleistocene East African saline-alkaline paleolacustrine deposit: Implications for Mars aqueous geochemistry

McHenry

Chevrier²,

Schröder

2011

J. Geophys. Res.

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“…The models were constructed to simulate the reaction of sulfuric acid with Cerro Negro basalt using the computer program EQ6, version 8.0 [ Wolery and Jarek , ; see also Bethke , ]. EQ6 is computationally equivalent to other computer programs that have been used to study weathering and the origin of sulfate‐rich deposits on Mars, including Geochemist's Workbench (GWB), GEOCHEQ, and CHESS [e.g., Elwood Madden et al ., ; Schiffman et al ., ; McAdam et al ., ; Berger et al ., ]. However, EQ6 was employed for this study because, unlike other programs, it allows solid solutions to be considered for mineral phases, which is essential for examination of compositional variations in minerals like those of the alunite‐jarosite group.…”

Section: Reaction Path Modelsmentioning

confidence: 99%

“…Berger et al . [] used a somewhat similar set of kinetic constraints to model alteration of Martian rocks by sulfuric acid solutions at 0°C. In their models, dissolution of the crystalline components of Martian basalt, represented by the rock Adirondack from Gusev Crater, were constrained by relative rate laws, such that olivine reacted more rapidly than plagioclase and pyroxene (glass was not considered as a component).…”

Section: Implications For Acid‐sulfate Alteration On Marsmentioning

confidence: 99%

Experimental study of acid‐sulfate alteration of basalt and implications for sulfate deposits on Mars

et al. 2013

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[1] Acid-sulfate alteration of basalt by SO 2 -bearing volcanic vapors has been proposed as one possible origin for sulfate-rich deposits on Mars. To better define mineralogical signatures of acid-sulfate alteration, laboratory experiments were performed to investigate alteration pathways and geochemical processes during reaction of basalt with sulfuric acid. Pyroclastic cinders composed of phenocrysts including plagioclase, olivine, and augite embedded in glass were reacted with sulfuric acid at 145 C for up to 137 days at a range of fluid : rock ratios. During the experiments, the phenocrysts reacted rapidly to form secondary products, while the glass was unreactive. Major products included amorphous silica, anhydrite, and Fe-rich natroalunite, along with minor iron oxides/oxyhydroxides (probably hematite) and trace levels of other sulfates. At the lowest fluid : rock ratio, hexahydrite and an unidentified Fe-silicate phase also occurred as major products. Reactionpath models indicated that formation of the products required both slow dissolution of glass and kinetic inhibitions to precipitation of a number of minerals including phyllosilicates and other aluminosilicates as well as Al-and Fe-oxides/oxyhydroxides. Similar models performed for Martian basalt compositions predict that the initial stages of acid-sulfate alteration of pyroclastic deposits on Mars should result in formation of amorphous silica, anhydrite, Fe-bearing natroalunite, and kieserite, along with relict basaltic glass. In addition, analysis of the experimental products indicates that Fe-bearing natroalunite produces a Mössbauer spectrum closely resembling that of jarosite, suggesting that it should be considered an alternative to the component in sulfate-rich bedrocks at Meridiani Planum that has previously been identified as jarosite.

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Assessing hydrodynamic effects on jarosite dissolution rates, reaction products, and preservation on Mars

et al. 2015

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Jarosite flow-through dissolution experiments were conducted in ultrapure water (UPW), pH 2 sulfuric acid, and saturated NaCl and CaCl 2 brines at 295-298 K to investigate how hydrologic variables may affect jarosite preservation and reaction products on Mars. K + -based dissolution rates in flowing UPW did not vary significantly with flow rate, indicating that mineral surface reactions control dissolution rates over the range of flow rates investigated. In all of the solutions tested, hydrologic variables do not significantly affect extent of jarosite alteration; therefore, jarosite is equally likely to be preserved in flowing or stagnant waters on Mars. However, increasing flow rate did affect the mineralogy and accumulation of secondary reaction products. Iron release rates in dilute solutions increased as the flow rate increased, likely due to nanoscale iron (hydr)oxide transport in flowing water. Anhydrite formed in CaCl 2 brine flow-through experiments despite low temperatures, while metastable gypsum and bassanite were observed in batch experiments. Therefore, observations of the hydration state of calcium sulfate minerals on Mars may provide clues to unravel past salinity and hydrologic conditions as well as temperatures and vapor pressures.

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How long was Meridiani Planum wet? Applying a jarosite stopwatch to determine the duration of aqueous diagenesis

Cited by 45 publications

References 35 publications

Jarosite in a Pleistocene East African saline-alkaline paleolacustrine deposit: Implications for Mars aqueous geochemistry

Jarosite in a Pleistocene East African saline-alkaline paleolacustrine deposit: Implications for Mars aqueous geochemistry

Experimental study of acid‐sulfate alteration of basalt and implications for sulfate deposits on Mars

Assessing hydrodynamic effects on jarosite dissolution rates, reaction products, and preservation on Mars

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