Modeling aluminum–silicon chemistries and application to Australian acidic playa lakes as analogues for Mars

Modeling hot spring chemistries with applications to martian silica formation

“…Also, the same case holds for silica depending on whether the precipitate is amorphous Si (Fig. 8) versus kaolinite or other clay minerals that are more insoluble than amorphous Si (Marion et al, 2009b).…”

“…The FREZCHEM model is structured to predict density and the effects of pressure on chemical equilibria (Marion et al, 2005(Marion et al, , 2009b(Marion et al, , 2010a. CHEMCHAU, on the other hand, is somewhat more limited with respect to density and pressure effects.…”

Mineralogical characterization of acid weathered phyllosilicates with implications for secondary martian deposits

“…Our present database is limited to simulations at 25 and 0°C; therefore, predicting mineral evolution at lower, more martian-relevant temperatures is limited. Indeed, temperature can have a marked effect on the stability of the precipitated minerals from the evaporation of a fluid, as freezing usually promotes low-temperature phases with greater levels of hydration (Marion et al, 2003(Marion et al, , 2008(Marion et al, , 2009). Yet, mineral alteration from acidic weathering began early in martian history, when temperatures may have been higher, at least locally, especially in periods of intense volcanism (Bullock and Moore, 2007;Zolotov and Mironenko, 2007;Halevy et al, 2008).…”

“…Modeling was accomplished using the Geochemist's Workbench (GWB) software, utilizing the React program and the thermo_phrqpitz database as previously described (Chevrier and Altheide, 2008). The database has been updated to include Fe-and Al-mineral solubilities (Tosca et al, 2008;Marion et al, 2009) and Pitzer ion interaction parameters (Marion et al, 2003(Marion et al, , 2008(Marion et al, , 2009Tosca et al, 2008).…”

Modeling ammonia–ammonium aqueous chemistries in the Solar System’s icy bodies

“…FREZCHEM is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions (to ionic strengths = 20 molal) using the Pitzer approach (Pitzer, 1991(Pitzer, , 1995 for the temperature range from 173 to 298 K (CHEMCHAU version has temperature range from 273 to 373 K) and the pressure range from 1 to 1000 bars (Marion and Farren, 1999;Marion, 2001Marion, , 2002Marion et al, 2003Marion et al, , 2005Marion et al, , 2006Marion et al, , 2009aMarion et al, , 2009bMarion et al, , 2010aMarion et al, , 2010bMarion et al, , 2011. Pressure beyond 1 bar was first added in Marion et al (2005).…”