An investigation into the effects of increasing salinity on photosynthesis in freshwater unicellular cyanobacteria during the late Archaean

Geobiology ◽  
2019 ◽  
Vol 17 (4) ◽  
pp. 343-359 ◽  
Author(s):  
Achim J. Herrmann ◽  
Michelle M. Gehringer
Keyword(s):  
Late Archaean

A copper isotope investigation of methane cycling in Late Archaean sediments

2021 ◽  
pp. 106267
Author(s):  
Natalya A.V. Zavina-James ◽  
Aubrey L. Zerkle ◽  
Robert C.J. Steele ◽  
Matthew R. Warke ◽  
Gareth Izon ◽  
...  
Keyword(s):  
Copper Isotope ◽  
Late Archaean ◽  
Methane Cycling

scholarly journals Palaeoclimates: the first two billion years

2006 ◽  
Vol 361 (1470) ◽  
pp. 917-929 ◽  
Author(s):  
James F Kasting ◽  
Shuhei Ono
Keyword(s):  
South Africa ◽  
Oxygen Isotopes ◽  
Natural Explanation ◽  
Witwatersrand Basin ◽  
Late Archaean ◽  
Bacterial Sulphate Reduction ◽  
Climatic Constraints ◽  
The Mean ◽  
High Concentrations ◽  
Earth’S Climate

Earth's climate during the Archaean remains highly uncertain, as the relevant geologic evidence is sparse and occasionally contradictory. Oxygen isotopes in cherts suggest that between 3.5 and 3.2 Gyr ago (Ga) the Archaean climate was hot (55–85 °C); however, the fact that these cherts have experienced only a modest amount of weathering suggests that the climate was temperate, as today. The presence of diamictites in the Pongola Supergroup and the Witwatersrand Basin of South Africa suggests that by 2.9 Ga the climate was glacial. The Late Archaean was relatively warm; then glaciation (possibly of global extent) reappeared in the Early Palaeoproterozoic, around 2.3–2.4 Ga. Fitting these climatic constraints with a model requires high concentrations of atmospheric CO 2 or CH 4 , or both. Solar luminosity was 20–25% lower than today, so elevated greenhouse gas concentrations were needed just to keep the mean surface temperature above freezing. A rise in O 2 at approximately 2.4 Ga, and a concomitant decrease in CH 4 , provides a natural explanation for the Palaeoproterozoic glaciations. The Mid-Archaean glaciations may have been caused by a drawdown in H 2 and CH 4 caused by the origin of bacterial sulphate reduction. More work is needed to test this latter hypothesis.

Isotope and rare earth element evidence for a late archaean terrane boundary in the southeastern pilbara craton, western australia

1992 ◽  
Vol 54 (2-4) ◽  
pp. 211-229 ◽  
Author(s):  
I.M. Tyler ◽  
I.R. Fletcher ◽  
J.R. de Laeter ◽  
I.R. Williams ◽  
W.G. Libby
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Western Australia ◽  
Earth Element ◽  
Late Archaean ◽  
Pilbara Craton

scholarly journals 207Pb-206Pb dating of magnetite, monazite and allanite in the central and northern Nagssugtoqidian orogen, West Greenland

2006 ◽  
Vol 11 ◽  
pp. 101-114 ◽  
Author(s):  
Henrik Stendal ◽  
Karsten Secher ◽  
Robert Frei
Keyword(s):  
Hydrothermal Activity ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Sulphide Deposit ◽  
Late Archaean ◽  
West Greenland ◽  
Isotopic Signatures ◽  
Source Characteristics ◽  
Isotopic Measurements

Pb-isotopic data for magnetite from amphibolites in the Nagssugtoqidian orogen, central West Greenland, have been used to trace their source characteristics and the timing of metamorphism. Analyses of the magnetite define a Pb-Pb isochron age of 1726 ± 7 Ma. The magnetite is metamorphic in origin, and the 1726 Ma age is interpreted as a cooling age through the closing temperature of magnetite at ~600°C. Some of the amphibolites in this study come from the Naternaq supracrustal rocks in the northern Nagssugtoqidian orogen, which host the Naternaq sulphide deposit and may be part of the Nordre Strømfjord supracrustal suite, which was deposited at around 1950 Ma ago. Pb-isotopic signatures of magnetite from the Arfersiorfik quartz diorite in the central Nagssugtoqidian orogen are compatible with published whole-rock Pb-isotopic data from this suite; previous work has shown that it is a product of subduction-related calc-alkaline magmatism between 1920 and 1870 Ma. Intrusion of pegmatites occurred at around 1800 Ma in both the central and the northern parts of the orogen. Pegmatite ages have been determined by Pb stepwise leaching analyses of allanite and monazite, and source characteristics of Pb point to an origin of the pegmatites by melting of the surrounding late Archaean and Palaeoproterozoic country rocks. Hydrothermal activity took place after pegmatite emplacement and continued below the closure temperature of magnetite at 1800– 1650 Ma. Because of the relatively inert and refractory nature of magnetite, Pb-isotopic measurements from this mineral may be of help to understand the metamorphic evolution of geologically complex terrains.

Late Archaean granites: a typology based on the Dharwar Craton (India)

2003 ◽  
Vol 127 (1-3) ◽  
pp. 103-123 ◽  
Author(s):  
J.-F. Moyen ◽  
H. Martin ◽  
M. Jayananda ◽  
B. Auvray
Keyword(s):  
Dharwar Craton ◽  
Late Archaean

Petrogenesis of Late Archaean Flood-Type Basic Lavas from the Klipriviersberg Group, Ventersdorp Supergroup, South Africa

1992 ◽  
Vol 33 (4) ◽  
pp. 817-847 ◽  
Author(s):  
J. S. MARSH ◽  
M. P. BOWEN ◽  
N. W. ROGERS ◽  
T. B. BOWEN
Keyword(s):  
South Africa ◽  
Late Archaean

The Chitradurga greenstone succession in south India and evolution of the late Archaean basin

1988 ◽  
Vol 125 (5) ◽  
pp. 507-519 ◽  
Author(s):  
P. K. Bhattacharyya ◽  
H. N. Bhattacharya ◽  
A. D. Mukherjee
Keyword(s):  
South India ◽  
Subsequent Development ◽  
Low Grade ◽  
Late Archaean ◽  
Clastic Sediments ◽  
Granitic Intrusion ◽  
Near Shore ◽  
Extensional Faulting ◽  
Wilson Cycle ◽  
Similar Deformation

AbstractThe Chitradurga greenstone succession of south India comprises a thick pile (~ 10 km) of late Archaean volcanic flows and terrigenous clastic sediments, metamorphosed from greenschist to low-grade amphilobite facies. An older near-shore sedimentary sequence of cratonic affiliation and an off-shore bimodal volcanic sequence were deposited contemporaneously on a gneissic basement. The volcanics are metasomatically altered, and major, minor and trace element data fail to discriminate the metavolcanics in terms of modern plate settings. A younger turbidite sequence of coarser elastics covered the older deposits without any apparent tectonic or erosional break. All the rocks of the succession display evidence of similar deformation, prior to invasion by younger granites (~ 2.5 Ga)in a late syn-kinematic phase.This suggests that initially a simple flat-lying downwarp in a continental crust served as the passive receptacle of the platform-type sediments, and also witnessed volcanism along extensional faulting. This phase of the basin was not associated with any compressive deformation. Subsidence of the Chitradurga basin by the denser volcanics and uplift in the gneissic borderlands provided the infrastructure for subsequent development of the younger turbidite sequence covering the still virtually undeformed older deposits. A compressive orogeny, accompanied by granitic intrusion (~ 2.5Ga) in a late kinematic phase, ultimately deformed and uplifted the basin-fill during the declining phase of basinal activity.There is no evidence in the belt to suggest that the plate-tectonic (Wilson cycle) processes, pending a terminal orogeny, were operative during evaluation of the Chitradurga basin.

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