AbGradCon 2010

The chemical compound of the earliest biont cytoplasm was probably identical to the environmental composition. In the publication [Natochin et al, 2008] has been given a supposition that the intracellular liquid’s physico-chemical parameters of modern creatures didn’t change. Therefore, the prebiotic terrestrial environment was possibly characterized by predominance of potassium above sodium (K/Na>1) and sufficiently high content of magnesium AbGradCon 2010 THE MAIN HYPOTHESIS * NaKK/NaMgCa Amoeba proteus, mmol/kg dry matter Mammal, mmol/l ~11 Human intracellular liquid, mmol/l *[Natochin et al, 2008]

AbGradCon 2010 During study of Karelia’s Achaean basalt weathering profiles [Alfimova and Matrenichev, 2006] it has been shown that only sodium was drastically removed from ancient weathering crust, whereas potassium was characterized by inert behavior Thus, a substratum, which may be a potassium donor for ancient water reservoir, should be characterized by considerable potassium content. An ancient weathering crust may be the similar substratum The modeled leaching of ancient crust rock (basaltic komatiite) under an carbon dioxide atmosphere [Novoselov and Silantyev, 2010] showed that the proportion of potassium and sodium in coexistent solution approximates to their proportion in initial rock (i.e. K/Na<1)

The main goal of this investigation is the numerical modeling of the earliest weathering crust forming Thermodynamic calculations with kinetic parameters were implemented on a basis of complex GEOCHEQ (thermodynamic data base derived from SUPCRT92) [Mironenko et al, 2008]. It has been written special code for modeling of weathering crust forming. This code simulates the many waves passage of aqueous solution with constant composition through the same solid block AbGradCon 2010

THE MODELING METHOD

AbGradCon 2010 THE CALCULATION PROCEDURE Primary minerals Secondary minerals [System composition] (t+t) = [Solution composition] t + Δ tΣ(Rate i S i ) Aqueous solution The kinetic control dissolution The thermodynamic control sedimentation The calculation of chemical equilibrium Dissolved matter during Δ t

AbGradCon 2010 THE MINERAL’S SOLUTION RATE EQUATION The Laidler empirical equation [Laidler, 1987] The Arrhenius equation [Xu et al., 1999 ] The Lasaga equation [Lasaga, 1981]

AbGradCon 2010 THE WEATHERING CRUST MODELING SCHEME t k =Σ Δt The single calculation duration was 0.05 year (t k ) waves went throw the modeling komatiitic block (k) Water-rock ratio was assumed to be (rainfall = 1000 mm per year) Temperature - 15°C [Monin, 1977] Atmosphere pressure - 1 bar

THE EARLY EARTH’S ATMOSPHERE AND HYDROSPHERE COMPOSITION PROBLEM

AbGradCon 2010 THE EARLY EARTH’S ATMOSPHERE COMPOSITION ? Hypotheses The volatiles stayed from primary Solar nebula The volatiles were brought by meteorites and comets The planetary matter degassing during accretion, global differentiation and later volcanic activity The primary volatiles source and composition The primary atmosphere compound was similar to Solar photosphere composition The earliest atmosphere compound corresponded to comet Haley composition (and other comets) or was C:H:O:N = 100:10:1:5* The primary atmosphere was destroyed due to Megaimpact. The secondary atmosphere was formed from mantle matter The planetesimal degassing during final phase of Earth’s accretion. The primary atmosphere approximated to volatile compound of C1 chondrite The earliest atmosphere compound corresponded to volcanic gas Links Signer and Suess, 1963; Selsis, 2004; Shapkin and Sidorov, 2004; Denlinger, 2005; Kulikov et al., 2007 Matsui and Abe, 1986; Fernandez and Ip, 1988; Chyba, 1991; Brandt and Chapman, 2004; Delsemme, 2006; *Dorofeeva (personal communication) Ozima and Podosek, 2002; Selsis, 2004; Maurette, 2006 Benlow and Meadows, 1977 Lammer et al., 2008 Pechernikova and Vityazev, 2008 Rubey, ; Anderson, 1975; Szalay, 1982; Lewis and Prinn, 1984; Elkins-Tanton, 2008

We don't have any reliable estimates for the chemical composition of earliest atmosphere and hydrosphere. However, it can be supposed that the chemistry of outer geospheres was by the interaction with mantle reservoir. Therefore, we considered the modern volcanic gas as a source for the atmosphere and hydrosphere analogues to the corresponding reservoirs of the early Earth Н2ОН2О83.14 Н2Н СО СО0.37 SO S2S H2SH2S0.60 HCl0.41 The composition of gases from Surtsey Volcano (Iceland), mol.%, [Gerlach, 1982] AbGradCon 2010 THE MODEL VOLATILES SOURCE

The calculation of the equilibrium composition of volcanic gases from Surtsey Volcano with T = 15°C and P = 1 bar yielded the compositions of aqueous solution (table) and gas phase consisting of CO 2 and minor amounts of water vapor CO 2 +HCO 3 - +CO E-02 CH E-25 CO1.03E-18 H 2 S+HS E-07 HSO 4 - +SO E-01 H2H2 3.57E-15 HCl1.37E-02 Cl E-01 pH0.44 The calculated composition of primary rainwater, mol/kg Н 2 О AbGradCon 2010 THE CALCULATED ATMOSPHERE AND RAINWATER COMPOSITIONS

RESULTS

AbGradCon 2010 SiO 2 * - amorphous silica, Dol - dolomite, Cpx – clinopyroxene, Gt – goethite, Ill – illite, Mgs – magnesite, Mag – magnetite, Ca-Mnt - Ca-montmorillonite, Na-Mnt - Na-montmorillonite Ol – olivine, Opx – orthopyroxene, and Py – pyrite Primary minerals of basaltic komatiite Secondary minerals of the weathering crust

AbGradCon 2010 The chemical weathering of basaltic komatiite is characterized by three main mineral assemblages: 1.Amorphous silica, carbonates, goethite and pyrite. The integral rock volume increases (up to 140% of initial rock volume). The duration is 7 years 2. Amorphous silica, goethite, montmorillonites and illite. The integral rock volume reduces. All primary minerals are dissolved at the end of this period. Solution pH drastically reduces. The duration of this stage is from 7 to 50 years 3. Amorphous silica, montmorillonites, illite and goethite. The integral rock volume reduces (up to 73% of initial rock volume). The duration of this stage is from 50 to 2000 years THE WEATHERING STAGES

Fresh rock7 years35 years100 years2000 years SiO 2 Al 2 O 3 Fe 2 O 3 FeO MgO CaO Na 2 O K 2 O H 2 O CO AbGradCon 2010 Initial solution 7 years35 years100 years2000 years K + Mg 2+ Ca 2+ Al 3+  C0 2 Si 4+  SO 4 2- Na + Cl - Fe 2+ pH 0.00E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E THE CHANGE OF ROCK AND SOLUTION COMPOSITIONS The results of our simulations demonstrate that sodium, calcium, magnesium and iron are almost completely removed in the course of the initial silicate minerals dissolution. But relative weight of silica and potassium increases. Potassium delivered to the solution participates in the formation of illite. And silica mostly accumulates as amorphous silica

AbGradCon 2010 INTERACTION IN HYDROSPHERE – WEATHERING CRUST SYSTEM W/R = 0.1 – K/Na = 6.8, pH final = 3.5 W/R = 10 – K/Na = 45, pH final = 0.5 K/Na ratio increases with rising of water- rock ratio

CALCULATED DATA AND INTRACELLULAR LIQUID CONPOSITION AbGradCon 2010

1. The weathering crust is formed as a result of the basaltic komatiite washing by aqueous solution in the course of 2000 years. It is eventually consisted from amorphous silica (96.4 vol.%) and illite (3.3 vol.%); 2. At final stage of the weathering crust forming the coexistent solution is characterized by high content of magnesium and predominance of potassium above sodium; 3. K/Na ratio increases with rising of water-rock ratio It is allowed to conclude that the weathering crust based on basaltic komatiite could be a source of cations for ancient water reservoir with favourable proportion for the origin of life We thank M.V. Mironenko for providing programs and consultations. This investigation was financially supported by program no. 15 of the Presidium of the Russian Academy of Sciences, subprogram 1, theme "Reconstruction of the Formation Conditions of the Protocrust of the Early Earth and Its Role in the Evolution of the Composition of the Primary Atmosphere and Hydrosphere" CONCLUSIONS AbGradCon 2010

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