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Abstract Earth surface redox conditions are intimately linked to the co-evolution of the geosphere and biosphere. Minerals provide a record of Earth’s evolving surface and interior chemistry in geologic time due to many different processes (e.g. tectonic, volcanic, sedimentary, oxidative, etc.). Here, we show how the bipartite network of minerals and their shared constituent elements expanded and evolved over geologic time. To further investigate network expansion over time, we derive and apply a novel metric (weighted mineral element electronegativity coefficient of variation; wMEECV) to quantify intra-mineral electronegativity variation with respect to redox. We find that element electronegativity and hard soft acid base (HSAB) properties are central factors in mineral redox chemistry under a wide range of conditions. Global shifts in mineral element electronegativity and HSAB associations represented by wMEECVchanges at 1.8 and 0.6 billion years ago align with decreased continental elevation followed by the transition from the intermediate ocean and glaciation eras to post-glaciation, increased atmospheric oxygen in the Phanerozoic, and enhanced continental weathering. Consequently, network analysis of mineral element electronegativity and HSAB properties reveal that orogenic activity, evolving redox state of the mantle, planetary oxygenation, and climatic transitions directly impacted the evolving chemical complexity of Earth’s crust.
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Uranium Redox and Deposition Transitions Embedded in Deep‐Time Geochemical Models and Mineral Chemistry Networks
Abstract Uranium (U) is an important global energy resource and a redox sensitive trace element that reflects changing environmental conditions and geochemical cycling. The redox evolution of U mineral chemistry can be interrogated to understand the formation and distribution of U deposits and the redox processes involved in U geochemistry throughout Earth history. In this study, geochemical modeling using thermodynamic data, and mineral chemistry network analysis are used to investigate U geochemistry and deposition through time. The number of U6+mineral localities surpasses the number of U4+mineral localities in the Paleoproterozoic. Moreover, the number of sedimentary U6+mineral localities increases earlier in the Phanerozoic than the number of U4+sedimentary mineral localities, likely due to the necessity of sufficient sedimentary organic matter to reduce U6+–U4+. Indeed, modeling calculations indicate that increased oxidative weathering due to surface oxygenation limited U4+uraninite (UO2) formation from weathered granite and basalt. Louvain network community detection shows that U6+forms minerals with many more shared elements and redox states than U4+. The range of weighted Mineral Element Electronegativity Coefficient of Variation (wMEECV) values of U6+minerals increases through time, particularly during the Phanerozoic. Conversely, the range of wMEECVvalues of U4+minerals is consistent through time due to the relative abundance of uraninite, coffinite, and brannerite. The late oxidation and formation of U6+minerals compared to S6+minerals illustrates the importance of the development of land plants, organic matter deposition, and redox‐controlled U deposition from ground water in continental sediments during this time‐period.
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- Award ID(s):
- 2020520
- PAR ID:
- 10490229
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geochemistry, Geophysics, Geosystems
- Volume:
- 25
- Issue:
- 2
- ISSN:
- 1525-2027
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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