Emergence of felsic crust and subaerial weathering recorded in Palaeoarchaean barite

Roerdink, Desiree L.; Ronen, Yuval; Strauß, Harald; Mason, Paul R.D.

doi:10.1038/s41561-022-00902-9

Cited by 17 publications

(12 citation statements)

References 55 publications

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“…3.8 Ga, indicating that more zircon grains younger than this age were likely generated from peraluminous crustal magma and/or during a moderate high-pressure fractionation process under horizontal tectonics ( 46 ). Placing a geodynamic transition before the earliest Archean is also supported by other relevant events such as the emergence of weathering and crustal rejuvenation by this time ( 49 – 52 ). Si and O isotopes are particularly sensitive to surface material recycling ( 11 ).…”

Section: Discussionmentioning

confidence: 77%

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No evidence of supracrustal recycling in Si-O isotopes of Earth’s oldest rocks 4 Ga ago

Zhang

Zhao

Zhou³

et al. 2023

Sci. Adv.

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Identifying the oldest evidence for the recycling of hydrated crust into magma on Earth is important because it is most effectively achieved by subduction. However, given the sparse geological record of early Earth, the timing of first supracrustal recycling is controversial. Silicon and oxygen isotopes have been used as indicators of crustal evolution on Archean igneous rocks and minerals to trace supracrustal recycling but with variable results. We present Si-O isotopes of Earth’s oldest rocks [4.0 billion years ago (Ga)] from the Acasta Gneiss Complex, northwest Canada, obtained using multiple techniques applied to zircon, quartz, and whole rock samples. Undisturbed zircon is considered the most reliable recorder of primary Si signatures. By combining reliable Si isotope data from the Acasta samples with filtered data from Archean rocks globally, we observe that widespread evidence for a heavy Si signature is recorded since 3.8 Ga, marking the earliest record of surface silicon recycling.

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Section: Discussionmentioning

confidence: 77%

“…transition before the earliest Archean is also supported by other relevant events such as the emergence of weathering and crustal rejuvenation by this time (49)(50)(51)(52). Si and O isotopes are particularly sensitive to surface material recycling (11).…”

Section: Earliest Si Isotopic Shift and Implicationsmentioning

confidence: 83%

No evidence of supracrustal recycling in Si-O isotopes of Earth’s oldest rocks 4 Ga ago

Zhang

Zhao

Zhou³

et al. 2023

Sci. Adv.

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“…Diagenetic processes tend to increase 87 Sr/ 86 Sr values when interstitial fluids are influenced by evolved K-bearing silicates (e.g., Shields and Veizer, 2002;Fairchild et al, 2018), or decrease Sr isotope composition when diagenetic fluids are influenced by mafic components, hydrothermal fluids or pressure solution of older, underlying carbonate rocks (e.g., Miller et al, 2008;Brand et al, 2010;Satkoski et al, 2017;Cui et al, 2020). Unfortunately, the well preserved, low-Mg calcite fossils, widely used in Phanerozoic SIS studies, are not available in Precambrian rocks, and so fine-grained carbonate components (e.g., diagenetic calcite microspar cement; Zhou et al, 2020), bulk carbonate rocks (e.g., micrite; Bailey et al, 2000) or non-carbonate rocks such as barite (e.g., McCulloch, 1994;Satkoski et al, 2016;Roerdink et al, 2022), gypsum or anhydrite (e.g., Kah et al, 2001) and francolite (Li et al, 2011) have all been used instead for this purpose. Apart from diagenetic alteration, the leaching of detrital aluminosilicate phases during sample preparation can also introduce unintended Sr contamination, which is either released by ion exchange during the initial leaching stage or aluminosilicate dissolution during the later leaching process (McArthur, 1994;Bailey et al, 2000;Bellefroid et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Effective leaching of argillaceous and dolomitic carbonate rocks for strontium isotope stratigraphy

CHEN¹,

Zhao²

2023

Preprint

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In recent years, various sample preparation methods have been developed to extract a primary Sr isotope signal from carbonate rocks. However, there has been little consensus around the best method due to natural variability in sample purity and mineralogy. For this study, we conducted systematic leaching experiments, focussing mainly on generally less favoured argillaceous and dolomitic limestones, using samples from the Mesoproterozoic Gaoyuzhuang Formation. Learning from previous studies, a multistep leaching approach was used to explore strontium isotope leaching systematics and extract near-primary isotopic ratios. For argillaceous and dolomitic limestone, the first 10%-30% dilute acetic acid leach, following an ammonium acetate (NH4Ac) prewash, yielded the lowest, demonstrably least altered seawater 87Sr/86Sr ratios. Subsequent dissolution steps exhibited significantly elevated 87Sr/86Sr, Rb/Sr, Al/Ca, and Mg/Ca ratios, indicating greater contributions from aluminosilicates and dolomite in the leachates. Lanthanide rare earth element and yttrium (REY) concentrations were also examined for each leaching step. In most cases, seawater-like REY patterns with the highest Y/Ho ratios (mostly > 36) occur in the first leaching step after ammonium acetate prewash, which is consistent with the Sr isotope study. However, one organic-rich sample (TOCtotal ~1.3%) with a near-seawater Sr isotope value exhibits a non-seawater-like REY pattern, possibly indicating that early diagenetic exchange during organic remineralization may influence the REY pattern of carbonate rocks without necessarily changing Sr isotopes. We applied previously proposed leaching cut-offs (preleach 30% ~ 40%, 60% ~ 70%), alongside the cut-off proposed from this study, for samples with various Mg/Ca and carbonate purities. We found that for the same argillaceous and dolomitic carbonate rocks, applying higher leaching cut-offs might cause sizeable error compared with targeting the first 10% ~ 30% directly after NH4Ac prewash. However, no significant differences were evident for high purity, and low Mg/Ca limestones, highlighting the importance of matching different sample types to the most appropriate dissolution method. Here we demonstrate that argillaceous, even partially dolomitized limestones could help fill gaps in the Precambrian seawater Sr isotope curve, especially where higher purity limestone successions are not readily available.

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“…Diagenetic processes tend to increase 87 Sr/ 86 Sr values when interstitial fluids are influenced by evolved K-bearing silicates (e.g., Shields andVeizer 2002, Fairchild et al 2018), or decrease Sr isotope composition when diagenetic fluids are influenced by mafic components, hydrothermal fluids or pressure solution of older, underlying carbonate rocks (e.g., Miller et al 2008, Brand et al 2010, Satkoski et al 2017, Cui et al 2020. Unfortunately, the well preserved, low-Mg calcite fossils, widely used in Phanerozoic SIS studies, are not available in Precambrian rocks, and so fine-grained carbonate components (e.g., diagenetic calcite microspar cement; Zhou et al 2020), bulk carbonate rocks (e.g., micrite; Bailey et al 2000) or non-carbonate rocks such as barite (e.g., McCulloch 1994, Satkoski et al 2016, Roerdink et al 2022, gypsum or anhydrite (e.g., Kah et al 2001) and francolite (Li et al 2011) have all been used instead for this purpose. Apart from diagenetic alteration, the leaching of detrital aluminosilicate phases during sample preparation can also introduce unintended Sr contamination, which is either released by ion exchange during the initial leaching stage or aluminosilicate dissolution during the later leaching process (McArthur 1994, Bailey et al 2000, Bellefroid et al 2018.…”

mentioning

confidence: 99%

“…2016, Roerdink et al . 2022), gypsum or anhydrite (e.g., Kah et al . 2001) and francolite (Li et al .…”

mentioning

confidence: 99%

Effective Leaching of Argillaceous and Dolomitic Carbonate Rocks for Strontium Isotope Stratigraphy

Chen,

Zhou

2023

Geostandard Geoanalytic Res

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Various methods have been developed to extract a primary seawater Sr isotope signal from carbonate rocks for strontium isotope stratigraphy. However, there is little consensus around the best method due to variable sample purity and mineralogy. For this study, we applied sequential leaching to a range of rock samples in order to explore strontium isotope leaching systematics of less favoured argillaceous and dolomitic limestone samples. Following an ammonium acetate (NH4Ac) prewash that removed ~ 10% of the carbonate fraction, a subsequent dilute acetic acid leach (10–30% aliquot) was shown to extract the lowest, demonstrably least altered seawater 87Sr/86Sr isotope ratios, along with in most cases seawater‐like rare earth element (REE) plus yttrium (Y) patterns with the highest Y/Ho ratios (mostly > 36). Subsequent dissolution steps exhibited significantly elevated 87Sr/86Sr isotope ratios, Rb/Sr, Al/Ca and Mg/Ca ratios, indicating greater contributions from aluminosilicates and dolomite in the leachates. The new dissolution method by comparison significantly increases the likelihood of obtaining primary seawater 87Sr/86Sr isotope ratios from argillaceous and dolomitic limestones where the other established procedures failed. Broad application of this approach could improve the temporal resolution of the seawater Sr isotope curve, especially where high purity limestone samples are scarce.

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Emergence of felsic crust and subaerial weathering recorded in Palaeoarchaean barite

Cited by 17 publications

References 55 publications

No evidence of supracrustal recycling in Si-O isotopes of Earth’s oldest rocks 4 Ga ago

No evidence of supracrustal recycling in Si-O isotopes of Earth’s oldest rocks 4 Ga ago

Effective leaching of argillaceous and dolomitic carbonate rocks for strontium isotope stratigraphy

Effective Leaching of Argillaceous and Dolomitic Carbonate Rocks for Strontium Isotope Stratigraphy

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