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McCollom, Thomas M; Robbins, James M; Moskowitz, Bruce; Berquo, Thelma; Jöns, Niels; Hynek, Bernhard (2013): (Table 7) Representative electron microprobe analyses for natroalunite and larger FeOx spheroids of experiment ADSU6. PANGAEA,, Supplement to: McCollom, TM et al. (2013): Experimental study of acid-sulfate alteration of basalt and implications for sulfate deposits on Mars. Journal of Geophysical Research: Planets, 118(4), 577-614,

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Acid-sulfate alteration of basalt by SO2-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. Reaction-path 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.
Latitude: 12.000000 * Longitude: -86.000000
Cerro-Negro * Latitude: 12.000000 * Longitude: -86.000000 * Method/Device: Multiple investigations (MULT) * Comment: The basalt cinders were collected from a recent eruption at Cerro Negro (1995) on a part of the volcano where there was no fumarolic activity.
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1MineralsMineralsJöns, Niels
2Silicon dioxideSiO2%Jöns, NielsElectron microprobe JEOL JXA 8900R
3Titanium dioxideTiO2%Jöns, NielsElectron microprobe JEOL JXA 8900R
4Aluminium oxideAl2O3%Jöns, NielsElectron microprobe JEOL JXA 8900R
5Chromium(III) oxideCr2O3%Jöns, NielsElectron microprobe JEOL JXA 8900R
6Iron oxide, Fe2O3Fe2O3%Jöns, NielsElectron microprobe JEOL JXA 8900R
7Magnesium oxideMgO%Jöns, NielsElectron microprobe JEOL JXA 8900R
8Calcium oxideCaO%Jöns, NielsElectron microprobe JEOL JXA 8900R
9Sodium oxideNa2O%Jöns, NielsElectron microprobe JEOL JXA 8900R
10Potassium oxideK2O%Jöns, NielsElectron microprobe JEOL JXA 8900R
11SulfiteSO3**2-%Jöns, NielsElectron microprobe JEOL JXA 8900R
12Phosphorus oxideP2O5%Jöns, NielsElectron microprobe JEOL JXA 8900R
13ChlorineCl%Jöns, NielsElectron microprobe JEOL JXA 8900R
14Elements, totalTotal%Jöns, NielsCalculated
42 data points

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