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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

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THE MAIN HYPOTHESIS

* Na K K/Na Mg Ca

Amoeba proteus, mmol/kg dry matter 26 376 14.5 217 63

Mammal, mmol/l 12 - 16 150 - 160 ~11

Human intracellular liquid, mmol/l 10 160 16 26 2

*[Natochin et al, 2008]

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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

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THE MODELING METHOD

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THE CALCULATION PROCEDURE

Primaryminerals

Secondaryminerals

[System composition](t+t) = [Solution composition]t + ΔtΣ(RateiSi)

Aqueous solution

The kineticcontrol dissolution

The thermodynamic control sedimentation

The calculation of chemical equilibrium

Dissolved matter during Δt

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THE MINERAL’S SOLUTION RATE EQUATION

Rate 0 0( .)0 0 2 0( ) ( / )m T T n l

H H O OH WH Hk a k k K a

)11(0 TTR

Ea

e

q

RT

Gpexp1

The Laidler empirical equation [Laidler, 1987]

The Arrhenius equation [Xu et al., 1999 ]

The Lasaga equation [Lasaga, 1981]

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THE WEATHERING CRUST MODELING SCHEME

tk=Σ Δt

The single calculation duration was 0.05 year (tk)

40 000 waves went throw the modeling komatiitic block (k)

Water-rock ratio was assumed to be 0.016 (rainfall = 1000 mm per year)

Temperature - 15°C [Monin, 1977]

Atmosphere pressure - 1 bar

THE EARLY EARTH’S ATMOSPHERE AND

HYDROSPHERE COMPOSITION PROBLEM

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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, 1977Lammer et al., 2008Pechernikova and Vityazev, 2008

Rubey, 1951-1955;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

Н2О 83.14

Н2 2.95

СО2 6.08

СО 0.37

SO2 2.57

S2 0.09

H2S 0.60

HCl 0.41

The composition of gases from Surtsey Volcano

(Iceland), mol.%, [Gerlach, 1982]

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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 CO2 and minor amounts of water vapor

CO2+HCO3-+CO3

2- 2.88E-02

CH4 9.54E-25

CO 1.03E-18

H2S+HS- 5.76E-07

HSO4-+SO4

2- 2.68E-01

H2 3.57E-15

HCl 1.37E-02

Cl- 2.47E-01

pH 0.44

The calculated composition of primary rainwater, mol/kg Н2О

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THE CALCULATED ATMOSPHERE AND

RAINWATER COMPOSITIONS

RESULTS

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SiO2* - 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

1 2 3

1 2 3

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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 rock 7 years 35 years 100 years 2000 years

SiO2

Al2O3

Fe2O3

FeOMgOCaONa2O

K2O

H2O

CO2

48.769.363.078.0421.658.050.900.160.000.00

41.067.837.551.576.7315.700.720.130.6217.86

57.2410.5811.600.446.903.680.380.172.416.20

74.277.7212.830.00080.471.150.300.223.040.00

98.331.130.0010.000.0050.100.0030.240.200.00

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Initial solution

7 years 35 years 100 years 2000 years

K+

Mg2+

Ca2+

Al3+

C02

Si4+

SO42-

Na+

Cl-

Fe2+

pH

0.00E+000.00E+000.00E+000.00E+004.60E-020.00E+002.62E-010.00E+002.60E-010.00E+000.445

5.86E-043.86E-011.44E-032.49E-097.55E-021.45E-032.54E-017.80E-032.59E-015.82E-035.857

4.35E-092.77E-019.91E-021.20E-025.82E-027.21E-062.61E-014.01E-032.59E-015.70E-045.446

1.58E-059.86E-043.13E-044.97E-034.69E-021.45E-032.62E-013.56E-042.60E-011.22E-020.491

1.43E-051.59E-053.00E-061.07E-044.69E-021.45E-032.62E-013.60E-062.60E-018.54E-070.446

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

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INTERACTION IN HYDROSPHERE –

WEATHERING CRUST SYSTEM

W/R = 0.1 – K/Na = 6.8, pHfinal = 3.5

W/R = 10 – K/Na = 45, pHfinal = 0.5

K/Na ratio increases with rising of water-rock ratio

CALCULATED DATA AND INTRACELLULAR LIQUID

CONPOSITION

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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

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THANK YOUFOR YOUR ATTENTION