Climatic and geochemical implications of Archean pedogenic gypsum in the Moodies Group (∼3.2 Ga), Barberton Greenstone Belt, South Africa

Nabhan, Sami; Luber, Tim; Scheffler, Franziska; Heubeck, Christoph

doi:10.1016/j.precamres.2016.01.011

Cited by 38 publications

(31 citation statements)

References 81 publications

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“…The background of the detectors was measured during the pre-sputtering and was then corrected for each analysis. The internal precision achieved under these conditions was better than 0.05‰ for δ 34 S and better than 0.03‰ for δ 33 S values (2σ). Several pyrite crystals (Maine: δ 34 S = -20.61‰, δ 33 S = -10.63‰; Spain: δ 34 S = -1.56‰, δ 33 S = -0.78‰; and Balmat: δ 34 S = +15.84‰, δ 33 S = +8.12‰) [38] were used to infer: (1) the instrumental mass fractionation and (2) the reference mass discrimination line, from which ∆ 33 S values were calculated.…”

Section: Sulfur Isotope Analyses By Simsmentioning

confidence: 79%

“…+1.4‰. Moreover, eight rounded pyrite grains from the Dycedale Syncline show negative ∆ 33 S values (between -0.59 and -0.11‰). The ∆ 33 S range of euhedral/subhedral pyrite grains is largely overlapped with the range of rounded grains, although the ∆ 33 S values of euhedral/subhedral grains are less varied than the values of rounded grains.…”

Section: Sulfur Isotopic Variation Through the Central Bgbmentioning

confidence: 97%

“…One sample from the Eureka Syncline (sample 12-007-1: 25°42′4.3″ S, 31°04′46.1″ E) is a conglomerate with a sandstone matrix from the base of unit MdQ1 of the Moodies Group (Figures 2a and b) [5,32]. The conglomerate contains common dolomitic clasts that are likely a rip-up clast from reworked carbonate crusts [33]. The pyrite grains in this conglomerate are mostly euhedral and range in size from 20 to 1000 μm ( Figure 3a).…”

Section: Lithofacies and Sulfide Description Of The Analyzed Rocksmentioning

confidence: 99%

“…The Archean rock record is characterized by the retention of mass-independent fractionation of sulfur isotopes (S-MIF) [14,15]. Sulfur has four stable isotopes ( 32 S, 33 S, 34 S, and 36 S) and a capital delta value is defined as a deviation from a mass-dependent fractionation (MDF) relationship using the following system of equations (e.g., [16]):…”

Section: Introductionmentioning

confidence: 99%

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Multiple Sulfur Isotope Records of the 3.22 Ga Moodies Group, Barberton Greenstone Belt

et al. 2020

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The Moodies Group, the uppermost unit in the Barberton Greenstone Belt (BGB) in South Africa, is a ~3.7-km-thick coarse clastic succession accumulated on terrestrial-to-shallow marine settings at around 3.22 Ga. The multiple sulfur isotopic composition of pyrite of Moodies intervals was newly obtained to examine the influence of these depositional settings on the sulfur isotope record. Conglomerate and sandstone rocks were collected from three synclines north of the Inyoka Fault of the central BGB, namely, the Eureka, Dycedale, and Saddleback synclines. The sulfur isotopic composition of pyrite was analyzed by Secondary Ion Mass Spectrometry (SIMS) for 6 samples from the three synclines and by Isotope Ratio Mass Spectrometry (IR-MS) for 17 samples from a stratigraphic section in the Saddleback Syncline. The present results show a signal of mass-independent fractionation of sulfur isotopes (S-MIF), although t-tests statistically demonstrated that the Moodies S-MIF signals (mostly 0‰ < ∆33S < +0.5‰) are significantly small compared to the signal of the older Paleoarchean (3.6–3.2 Ga) records. These peculiar signatures might be related to initial deposition of detrital pyrite of juvenile origin from the surrounding intrusive (tonalite–trondhjemite–granodiorite; TTG) and felsic volcanic rocks, and/or to secondary addition of hydrothermal sulfur during late metasomatism. Moreover, fast accumulation (~0.1–1 mm/year) of the Moodies sediments might have led to a reduced accumulation of sulfur derived from an atmospheric source during their deposition. As a result, the sulfur isotopic composition of the sediments may have become susceptible to the secondary addition of metasomatic sulfur on a mass balance point of view. The sulfur isotopic composition of Moodies pyrite is similar to the composition of sulfides from nearby gold mines. It suggests that, after the Moodies deposition, metasomatic pyrite formation commonly occurred north of the Inyoka Fault in the central BGB at 3.1–3.0 Ga.

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Section: Sulfur Isotope Analyses By Simsmentioning

confidence: 79%

Section: Sulfur Isotopic Variation Through the Central Bgbmentioning

confidence: 97%

Section: Lithofacies and Sulfide Description Of The Analyzed Rocksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multiple Sulfur Isotope Records of the 3.22 Ga Moodies Group, Barberton Greenstone Belt

et al. 2020

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“…The geology within the study areas consist of the Barberton Greenstone Belt (BGB) located in north-eastern South Africa and forms part of the Archean Kaapvaal Craton [21,22]. The lowermost, ca.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Surface and Trapped Dust Samples Collected around Human Settlements That are in the Vicinity of Old Mine Tailings in Mpumalanga Province, South Africa

Moja¹,

Kwata²,

Sebesho³

et al. 2016

J Earth Sci Clim Change

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The Moodies Group—a High-Resolution Archive of Archaean Surface Processes and Basin-Forming Mechanisms

Heubeck

2019

Regional Geology Reviews

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Climatic and geochemical implications of Archean pedogenic gypsum in the Moodies Group (∼3.2 Ga), Barberton Greenstone Belt, South Africa

Cited by 38 publications

References 81 publications

Multiple Sulfur Isotope Records of the 3.22 Ga Moodies Group, Barberton Greenstone Belt

Multiple Sulfur Isotope Records of the 3.22 Ga Moodies Group, Barberton Greenstone Belt

Characterization of Surface and Trapped Dust Samples Collected around Human Settlements That are in the Vicinity of Old Mine Tailings in Mpumalanga Province, South Africa

The Moodies Group—a High-Resolution Archive of Archaean Surface Processes and Basin-Forming Mechanisms

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