Recently, a large number of geochemical and geological data on Archean have been obtained and the atmospheric gaseous oxygen (O₂), carbon dioxide (CO₂) and methane (CH₄) concentrations were estimated based on these data.
P_O2 (oxygen partial pressure) of Archean (3.8-2.5 billion age) atmosphere was estimated to be very low (10^-5 PAL) from Paleosol compositions (FeO, trace elements, nitrogen isotope), sulfur isotopic composition of sedimentary rocks and presence of major banded iron formation and uranium deposits.
P_CO2 (carbon dioxide partial pressure) was estimated to be 10^-2.5-10 atm and 10^-2.5-10^-3.5 atm from dynamic equilibrium and chemical equilibrium model, respectively.
Recently, it was cited that sulfur isotopic composition of the sedimentary rocks cannot be explained by mass dependent isotopic fractionation but can be by mass independent fractionation.
Holland, Kasting, Pavlov and others inferred from these evidence that the Archean atmosphere was characterized by low O₂, high CO₂ and high CH₄ concentrations. Their theory is widely accepted. In contrast Ohmoto and others insist oxygen-rich Archean atmosphere. For example, Ohmoto et al. (2006) and Watanabe and Ohmoto (2007) inferred that mass independent sulfur isotopic fractionation links to thermal and biological evolution of earth (thermal and chemical reduction of sulfate in sedimentary and diagenetic processes). Ohmoto and his associates postulate an essentially constant atmospheric P_O2 level since ∼ 4Ga.
We need to study the deviation from chemical equilibrium between waters and rocks, mechanism of water-rock interaction, mass independent sulfur isotopic fractionation, mechanism of methane generation and flux to precisely estimate Archean P_O2, P_CO2 and P_CH4.

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This study estimates the influence of surface morphology of specimen on actual quantitative analysis results measured using the wavelength dispersive spectrometer (WDS) detector and the energy dispersive spectrometer (EDS) detector. The polishing plane of mineral specimens can yield reliable and reproducible results from the WDS measurement, but the measurement errors become larger with an increase of the surface roughness. On the other hand, the EDS semi-quantitative results greatly deviate from the ideal chemical compositions of minerals regardless of their surface roughness. Since rigorous quantitative analysis of a mineral is based on determining an intensity ratio between a characteristic X-ray peak in the mineral and the same peak in a standard measured under identical operating conditions, the measurement errors of chemical composition occur unless the X-ray intensities can be accurately measured under the identical conditions. Serious measurement errors may bring us to mischaracterized interpretations and erroneous descriptions.

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