Continentally-derived solutes in shallow Archean seawater: Rare earth element and Nd isotope evidence in iron formation from the 2.9Ga Pongola Supergroup, South Africa

Alexander, Brian W.; Bau, Michael; Andersson, Per; Dulski, Peter

doi:10.1016/j.gca.2007.10.028

Cited by 326 publications

(121 citation statements)

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“…In many Archaean and early Palaeoproterozoic IFs there are no Ce anomalies (Planavsky et al, 2010a), and thus no deviation from trivalent Ce behaviour (e.g., Fryer, 1977a;Bau and Möller, 1993;Bau et al, 1997;Alexander et al, 2008;Frei et al, 2008). This suggests that the water column from which Fe(III) oxyhydroxides precipitated was relatively anoxic, or at least below the Eh of the Ce 4+ /Ce 3+ redox couple (Bau and Dulski, 1996).…”

Section: Iron Formations As Tracers Of Seawater Redoxmentioning

confidence: 99%

“…Both Ce and Nd have short residence times in the modern ocean, 90-165 and 1000-1500 years, respectively (Amakawa et al, 1996), and in the Archaean oceans these elements likely had a similar residence times on the order of 10 3 years, suggesting that Ce and Nd isotope compositions would be spatially heterogeneous. In the Archaean and Proterozoic oceans, ε Nd (t) values (which describe the deviation of the 143 Nd/ 144 Nd ratio measured in a sample relative to the 143 Nd/ 144 Nd ratio in a chondritic uniform reservoir at time t and in parts per 10 4 ) are estimated to have been +1 to +2 for deep waters dominated by hydrothermal sources, whereas values down to -3 would have been typical of shallow-waters dominated by terrestrial sources (Miller and O'Nions, 1985;PimentelKlose, 1988a, 1988b;Alexander et al, 2008). The relative contribution of continentally-sourced versus mantle-sourced REE+Y, discussed in more detail in the next section, has been estimated using Ce and Nd isotope compositions Wasserburg, 1980, Bau et al, 1997;Shimizu et al, 1990;Alexander et al, 2008;2009;Viehmann et al, 2015).…”

mentioning

confidence: 99%

“…In the Archaean and Proterozoic oceans, ε Nd (t) values (which describe the deviation of the 143 Nd/ 144 Nd ratio measured in a sample relative to the 143 Nd/ 144 Nd ratio in a chondritic uniform reservoir at time t and in parts per 10 4 ) are estimated to have been +1 to +2 for deep waters dominated by hydrothermal sources, whereas values down to -3 would have been typical of shallow-waters dominated by terrestrial sources (Miller and O'Nions, 1985;PimentelKlose, 1988a, 1988b;Alexander et al, 2008). The relative contribution of continentally-sourced versus mantle-sourced REE+Y, discussed in more detail in the next section, has been estimated using Ce and Nd isotope compositions Wasserburg, 1980, Bau et al, 1997;Shimizu et al, 1990;Alexander et al, 2008;2009;Viehmann et al, 2015). In some cases, 138 Ce systematics show that Ce anomalies in IFs are a feature produced by recent hydrothermal events and are not intrinsic to ancient seawater (Hayashi et al, 2004).…”

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confidence: 99%

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Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

Konhauser

Planavsky

Hardisty

et al. 2017

Earth-Science Reviews

382

257

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Section: Iron Formations As Tracers Of Seawater Redoxmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

Konhauser

Planavsky

Hardisty

et al. 2017

Earth-Science Reviews

382

257

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“…The relative exposure area of igneous rocks at Earth's surface has ostensibly varied very little throughout the entire Phanerozoic 104 (the last ~500 million years of Earth's history), despite a cycle of supercontinent assembly and break-up during the late Paleozoic. In addition, recent data place the onset of significant crustal growth, recycling, emergence and surface weathering very early in Earth's history [131][132][133][134][135][136][137][138] . This is perhaps not surprising -the record of sedimentary rocks on Earth extends to ~3.8 billion years ago and is continuous from this point onward, suggesting qualitatively that a surface sedimentary rock cycle existed during Earth's earliest history.…”

Section: The Balance Between Igneous and Sedimentary Sulphur Sourcesmentioning

confidence: 99%

Long-term sedimentary recycling of rare sulphur isotope anomalies

Reinhard

Planavsky

Lyons

2013

Nature

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Sulphur Isotope Database:An extensive sulphur isotope database was used in the construction of Main Text Figure 1. These data were compiled from primary references 1-37 , although in some cases age constraints for certain units were obtained from other sources [38][39][40][41] or estimated. For Main Text Figure 1b, we calculated the cumulative average ∆ 33 S value for all samples up to each year of publication. The average values reported here thus include some contribution from sulphate minerals. However, the overwhelming majority of the data are sulphide mineral phases, and given that most sulphate data are characterized by negative ∆ 33 S values their inclusion will largely attenuate the pattern emphasized here, rendering our argument conservative. Furthermore, the overall effect of their inclusion is quite small (Fig. S1a,b). We also examined the effect of filtering data from analyses made via secondary ion mass spectrometry (SIMS) and analyses of macroscopic pyrite textures, which are not likely to be representative of bulk weathering crust, but again note that the basic pattern remains unchanged (Fig. S1a,b).The mean ∆ 33 S values shown in Fig. 1 are presented as unweighted averages. We consider this approach qualitatively justified, in that the database is composed largely of fine-grained siliciclastic sedimentary rocks that are relatively organic carbon and sulphur rich. Such rocks will not only be, on average, the most sulphur-enriched phases of the crust, but they will also likely hold the majority of the weathering sulphur reservoir at Earth's surface. Nonetheless, it is important to consider the possibility that there is a bias related to systematic relationships between the sulphur content of sedimentary rocks and their ∆ 33 S value. For this purpose, we compiled the available sulphur concentration data for the units within the isotope database and performed concentration-weighted statistical analyses.There does not appear to be any systematic relationship between rare sulphur isotope composition and sulphur content within the database (Fig. S2a). In addition, the cumulative unweighted average is nearly indistinguishable from the concentration-weighted average within this subset of the database (Fig. S2a,b). When the evolution of the overall ∆ 33 S value of the database is concentration-weighted, it shows a generally similar pattern through time to that of the overall mean values (Fig. S2b). Indeed, the mean ∆ 33 S value when weighted by concentration is more positive than the unweighted mean for a given population from the database. We stress the caveat that many of the published rare sulphur isotope datasets do not contain sulphur concentration data, so unfortunately this analysis cannot be performed on the entire database. However, the coupled isotope and concentration data represent well over 500 samples that range in sulphur content over three orders of magnitude. These considerations lead us to conclude that the pattern expressed in the overall mean ∆ 33 S values through time is robust and is ...

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“…8A) and slightly positive (La/La*) CN = 0.74-1.8 and (Gd/Gd*) CN = 0.95-27.88 anomalies (Table 2) of the Farsesh barite samples deposited in the marine environment (cf. Chen et al, 2006;Alexander et al, 2008). The REE pattern of the Farsesh barite samples exhibit a positive Eu anomaly ranging from (Eu/Eu*) CN = 1.93 to 11.54 (Table 2), suggesting that these samples were deposited from exhalative hydrothermal fluids (cf.…”

Section: Rare Earth Elementsmentioning

confidence: 99%

Geochemistry and Fuid-Inclusion Microthermometry of the Farsesh Barite Deposit, Iran

et al. 2014

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The Permian carbonate-hosted Farsesh barite deposit is located southeast of the City of Aligudarz in the province of Lorestan, Iran. Structurally, this deposit lies in the Zagros metallogenic belt and the Sanandaj-Sirjan Zone. Barite mineralisations occur as open-space flling veins, and as massive and replacement ores along fractures, faults and shear zones of the Permian carbonate host rocks. In order to determine the structure, in addition to pe-trographic and fuid-inclusions studies, an ICP-MS analysis was carried out in order to measure the major as well as the trace and rare earth elements. The Farsesh barite deposit has a simple mineralogy, of which barite is the main mineral, followed by calcite, dolomite, quartz, and opaque minerals such as Fe-oxides. Replacement of bar-ite by calcite is common and is more frequent than space-flling mineralisation. Sulphide minerals are minor and mainly consist of chalcopyrite and pyrite, which are altered by weathering to covellite, malachite and azurite. Petrographic analysis and micro-thermometry were carried out on the two-phase liquid/vapour inclusions in ellipsoidal or irregularly shaped minerals ranging in size from 5–10 µm. The measurements were conducted on fuid inclusions during the heating and subsequent homogenisation in the liquid phase. The low homogenisation temperatures (200–125°C) and low to moderate salinity (4.2–20 eq wt% NaCl) indicate that the barite had precipitated from hydrothermal basinal water with low to moderate salinity. It appears from the major and trace elements that geochemical features such as Ba and Sr enrichment in the barite samples was accompanied by depletion of Pb, Zn, Hg, Cu and Sb. The geochemistry of the rare earth elements, such as low σREE concentrations, LREE-enrichment chondrite-normalised REE patterns, the negative Ce and positive Eu anomalies, the low Ce/La ratio and the positive La and Gd anomalies, suggest that the Farsesh barite was deposited from hydrothermally infuenced sea water. The Farsesh deposit contains low-temperature hydrothermal barite. The scatter plots of the barite (close to sea water) in different areas on the CeN/SmN versus CeN/YbN diagram support the possibility that the barite was formed from seawater-bearing hydrothermal fuids.

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Continentally-derived solutes in shallow Archean seawater: Rare earth element and Nd isotope evidence in iron formation from the 2.9Ga Pongola Supergroup, South Africa

Cited by 326 publications

References 68 publications

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

Long-term sedimentary recycling of rare sulphur isotope anomalies

Geochemistry and Fuid-Inclusion Microthermometry of the Farsesh Barite Deposit, Iran

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