Redox fluctuation and δ13Corg-δ34S perturbations recorded in the 1.9 Ga Nuvilik Formation of the Cape Smith belt, Canada

Motomura, Kento; Kiyokawa, Shoichi; Ikehara, Masaaki; Sano, Takashi; Bleeker, Wouter; Tanaka, Kentaro; Miki, Takashi; Sano, Yuji

doi:10.1016/j.precamres.2021.106191

Cited by 6 publications

(5 citation statements)

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“…A typical example of such fluctuation is a transient elevation of the supply rate of Fe(II) caused by the eruption of large igneous provinces (LIPs) (Isley & Abbott, 1999; Rasmussen et al, 2012). This is consistent with the suggested LIP‐induced redox fluctuation at ~1.9 Ga based on C and S isotope signatures (Motomura et al, 2021). After the period of extensive IF deposition at ~1.9–1.8 Ga, the amount of IF became negligibly small (Figure 1b).…”

Section: Discussionsupporting

confidence: 91%

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Evolution of iron and oxygen biogeochemical cycles during the Precambrian

Watanabe,

Tajika,

Ozaki

2023

Geobiology

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Iron (Fe) is an essential element for life, and its geochemical cycle is intimately linked to the coupled history of life and Earth's environment. The accumulated geologic records indicate that ferruginous waters existed in the Precambrian oceans not only before the first major rise of atmospheric O2 levels (Great Oxidation Event; GOE) during the Paleoproterozoic, but also during the rest of the Proterozoic. However, the interactive evolution of the biogeochemical cycles of O2 and Fe during the Archean–Proterozoic remains ambiguous. Here, we develop a biogeochemical model to investigate the coupled biogeochemical evolution of Fe–O2–P–C cycles across the GOE. Our model demonstrates that the marine Fe cycle was less sensitive to changes in the production rate of O2 before the GOE (atmospheric pO2 < 10−6 PAL; present atmospheric level). When the P supply rate to the ocean exceeds a certain threshold, the GOE occurs and atmospheric pO2 rises to ~10−3–10−1 PAL. After the GOE, the marine Fe(II) concentration is highly sensitive to atmospheric pO2, suggesting that the marine redox landscape during the Proterozoic may have fluctuated between ferruginous conditions and anoxic non‐ferruginous conditions with sulfidic water masses around continental margins. At a certain threshold value of atmospheric pO2 of ~0.3% PAL, the primary oxidation pathway of Fe(II) shifts from the activity of Fe(II)‐utilizing anoxygenic photoautotrophs in sunlit surface waters to abiotic process in the deep ocean. This is accompanied by a shift in the primary deposition site of Fe(III) hydroxides from the surface ocean to the deep sea, providing a plausible mechanistic explanation for the observed cessation of iron formations during the Proterozoic.

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Section: Discussionsupporting

confidence: 91%

“…This might have worked (Isley & Abbott, 1999;Rasmussen et al, 2012). This is consistent with the suggested LIP-induced redox fluctuation at ~1.9 Ga based on C and S isotope signatures (Motomura et al, 2021). After the period of extensive IF deposition at ~1.9-1.8 Ga,theamountofIFbecamenegligiblysmall(Figure 1b).…”

Section: Discussionsupporting

confidence: 84%

Evolution of iron and oxygen biogeochemical cycles during the Precambrian

Watanabe,

Tajika,

Ozaki

2023

Geobiology

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“…It is worth noting that many of the sedimentary samples reported in previous studies are in close proximity to the mafic-ultramafic complexes, so it is possible that their measured compositions have been affected by moderate extents of devolatilization which may lead to underestimated C and S concentrations of the assimilant in our models. For example, the distal and unmetamorphosed shale samples collected from the Nuvilik Formation at Raglan area are characterized as having higher C and lower S contents than that used in this study (Motomura et al, 2021). By inserting these shale compositions into the model, we found that a tiny fraction of assimilant (< 1%) is enough to cause Pt alloy saturation which is in consensus with the model results shown above.…”

Section: Resultssupporting

confidence: 85%

“…Taking organic matter into account in the model would lead to more extreme estimates of the degree of reduction of the magma and strengthen our argument because oxidation of hydrocarbons containing C -4 (e.g., CH4) requires twice the net amount of reactant O to convert one mole of C to CO2. Although potential crustal rocks (i.e., assimilants) such as sediments from the Nuvilik Formation at Raglan (Motomura et al, 2021) or Noril'sk (Iacono-Marziano et al 2012a) have been suggested to have contained a significant amount of organic matter, native iron occurrences are rare. The absence of native iron may be attributed to the stability of graphite and undersaturation of native iron in mafic and ultramafic melt at relatively high pressures (>120 bar; Iacono-Marziano et al, 2012a), however, there is no evidence suggesting that extremely reducing conditions (e.g., ΔFMQ < -6) have been reached at any of the studied localities so we have chosen to take the conservative route of treating all C as graphite in all C-bearing sediments and lower crustal rocks assimilation modeling.…”

Section: Alphamelts Modelsmentioning

confidence: 99%

Petrogenesis of Massive Sulfide Ores and Associated Globular Sulfide Texture in Raglan Horizon: Implications for Exploration of Concealed Orebodies at Depth

Li¹

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First and foremost, I would like to express my sincere gratitude to my thesis supervisor, Dr. Jim Mungall of the department of Earth Science at Carleton University, for his consistent and generous support, and for his enthusiasm which has motivated me to further pursuits in the field of geology. Jim accepted me as a rookie in the field of magmatic sulfide and showed me a whole new perspective on geology. This work would not be possible without his wisdom and long-lasting patience during the course of my study in Carleton.My gratitude also goes to my friends and colleagues Chris Jenkins, William Smith, Claudia Augustin, Rafael Bacha, Zhuosen Yao, and Nabil Shawwa who have provided me with many suggestions and welcomed me to the family. Special thanks go to Maryam Shahabi Far who has provided valuable and consistent supports in conducting SEM analyses. I would also like to thank Francois Baillargeon and other geology staff at Glencore's Raglan mine for granting me access to the legacy database, for their critical support during the field work, and for their constructive comments. Financial support from Carleton University and the Natural Sciences and EngineeringResearch Council of Canada is greatly appreciated.Last but not least, I would like to thank my family for years of unwavering support and encouragement. I am forever in debt to them. Thank you.v PrefaceThis thesis is presented as three independent chapters (Chapters 2-4) which are drawn directly from manuscripts that are published or in the process of submission to highly rated, peer-reviewed scientific journals at the time of thesis submission. I am the lead author of all the chapters. In all research chapters, the thesis supervisor, Dr. Jim Mungall has been integral to project development, data analysis, modeling, and manuscript editing. Each of these chapters is formatted as a standalone manuscript with an abstract, introduction, methods, results, discussions, and conclusions. The supplementary data from each manuscript is compiled and forms the appendices of this thesis. As a result of this formatting choice, there is some repetition, particularly pertaining to regional geology sections.Chapter 2 is titled "Chalcophile element heterogeneity in Ni-Cu-(PGE) orebodies of Raglan Horizon in Cape Smith Belt: Implications for ore-forming processes".

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“…The δ 34 S values of pyrite formed during early diagenesis are similar to those of SO 4 2– -reduced sulfides. Due to the Rayleigh fractionation effect, the δ 34 S values of pyrite formed in the late diagenesis stage will gradually increase. − Therefore, the pyrite formation period was determined according to the difference in sulfur isotopes in different pyrite forms. Framboidal pyrite is generally considered to have formed during syn-sedimentary and early diagenetic stages, with a small grain size and negative sulfur isotopes.…”

Section: Introductionmentioning

confidence: 99%

Pyrite Characteristics in Lacustrine Shale and Implications for Organic Matter Enrichment and Shale Oil: A Case Study from the Triassic Yanchang Formation in the Ordos Basin, NW China

Zhou,

Liu,

et al. 2024

ACS Omega

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Pyrite is widely distributed in lacustrine shales and has become a research focus in unconventional oil and gas exploration. Pyrite morphology is useful for identifying different types of organic matter and assessing shale oil enrichment in organic-rich shale. Abundant pyrite is developed in the source rocks from the Chang 7 Member of the Yanchang Formation in the Ordos Basin, NW China. However, the relationship between different pyrite types and the differential enrichment of shale oil still needs to be clarified. The organic geochemistry, petrology, and isotopic composition of the Chang 7 Member samples were analyzed. The significance of pyrite types and sulfur isotopic compositions as indicators of depositional environments and shale oil enrichment was emphasized. The Chang 7 shales contain three pyrite morphologies, framboidal pyrite (type A), spherulitic pyrite (type B), and euhedral and anhedral pyrite (type C), and their aggregates. The sulfur isotopic compositions of pyrite (δ 34 S py ) in Chang 7 shales with different pyrite types exhibited regular patterns. The δ 34 S values of types A, B, and C pyrites were sequentially positive overall (average values are −2.739, 2.201, and 7.487‰ in sequence), indicating that type A pyrite was formed during the syn-sedimentary to early diagenetic stage and types B and C pyrites were formed during the early to middle diagenetic stage. Types A, B, and C pyrites showed sequentially increasing kerogen type index values and kerogen carbon isotope values (mean values of −31.59, −28.70, and −26.45‰, successively), indicating that the horizons where types A, B, and C pyrites developed correspond to types I, II, and III organic matter, respectively. Strong correlations between the pyrite content and oil components reveal that pyrite indicates shale oil enrichment. Moreover, variations in pyrite type significantly influenced the enrichment behavior of shale oil. Types A and B pyrites contributing to reservoir space showed shale oil enrichment. They promoted saturated hydrocarbon enrichment at >15% pyrite content, whereas type C pyrite did not indicate shale oil enrichment. These findings provide new insights into the differential enrichment of organic matter and shale oil and valuable guidance for the large-scale exploration and development of shale oil resources.

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Redox fluctuation and δ13Corg-δ34S perturbations recorded in the 1.9 Ga Nuvilik Formation of the Cape Smith belt, Canada

Cited by 6 publications

References 63 publications

Evolution of iron and oxygen biogeochemical cycles during the Precambrian

Evolution of iron and oxygen biogeochemical cycles during the Precambrian

Petrogenesis of Massive Sulfide Ores and Associated Globular Sulfide Texture in Raglan Horizon: Implications for Exploration of Concealed Orebodies at Depth

Pyrite Characteristics in Lacustrine Shale and Implications for Organic Matter Enrichment and Shale Oil: A Case Study from the Triassic Yanchang Formation in the Ordos Basin, NW China

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