Geochemical environments of the Archean-Proterozoic
نویسندگان
چکیده
منابع مشابه
Iron isotope composition of some Archean and Proterozoic iron formations
Fe isotopes can provide new insight into redox-dependent biogeochemical processes. Precambrian iron formations (IF) are deserving targets for Fe isotope studies because they are composed predominantly of authigenic Fe phases and record a period of unprecedented iron deposition in Earth’s history. We present Fe isotope data for bulk samples from 24 Archean and Proterozoic IF and eight Phanerozoi...
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A provenance study was conducted on the Mid-Proterozoic Newland Formation, in which petrographical features of sandstones and geochemical characteristics of shales were integrated to arrive at an internally consistent interpretation. Sandstones of the Newland Formation are typically arkosic sands and arkoses with very well rounded quartz and feldspar grains and only minor amounts of extrabasina...
متن کاملGeochemical comparison between Archaean and Proterozoic orthogneisses from the Nagssugtoqidian orogen, West Greenland
In the Palaeoproterozoic Nagssugtoqidian orogen of West Greenland reworked Archaean and juvenile Proterozoic orthogneisses occur side by side and are difficult to differentiate in the field. Archaean gneisses have tonalitic to trondhjemitic compositions with relatively low Al2O3 and Sr, and may have been derived from magmas formed by melting of basaltic or amphibolitic rocks at moderate pressur...
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Bio-signatures play a central role in determining whether life existed on early Mars. Using a terrestrial basalt as a compositional analog for the martian surface, we applied a combination of experimental microbiology and thermochemical modeling techniques to identify potential geochemical bio-signatures for life on early Mars. Laboratory experiments were used to determine the short-term effect...
متن کاملA theory of atmospheric oxygen.
Geological records of atmospheric oxygen suggest that pO2 was less than 0.001% of present atmospheric levels (PAL) during the Archean, increasing abruptly to a Proterozoic value between 0.1% and 10% PAL, and rising quickly to modern levels in the Phanerozoic. Using a simple model of the biogeochemical cycles of carbon, oxygen, sulfur, hydrogen, iron, and phosphorous, we demonstrate that there a...
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ژورنال
عنوان ژورنال: Доклады Академии наук
سال: 2019
ISSN: 0869-5652
DOI: 10.31857/s0869-56524884403-407