The mineral dissolution rate conundrum: Insights from reactive transport modeling of U isotopes and pore fluid chemistry in marine sediments

Maher, Kate; Steefel, Carl I.; DePaolo, Donald J.; Viani, B.E.

doi:10.1016/j.gca.2005.09.001

Cited by 241 publications

(223 citation statements)

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“…Similarly, K other is also assumed to be constant. The concentration of uranium in carbonates is estimated by converting the moles of U in the seawater reservoir, N sw , and assuming constant seawater calcium concentrations and a distribution coefficient of 1.4 (38). Fig.…”

Section: Methodsmentioning

confidence: 99%

Marine anoxia and delayed Earth system recovery after the end-Permian extinction

Lau

Maher

Altıner

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Delayed Earth system recovery following the end-Permian mass extinction is often attributed to severe ocean anoxia. However, the extent and duration of Early Triassic anoxia remains poorly constrained. Here we use paired records of uranium concentrations ([U]) and 238 U/ 235 U isotopic compositions (δ 238 U) of Upper Permian−Upper Triassic marine limestones from China and Turkey to quantify variations in global seafloor redox conditions. We observe abrupt decreases in [U] and δ 238 U across the end-Permian extinction horizon, from ∼3 ppm and −0.15‰ to ∼0.3 ppm and −0.77‰, followed by a gradual return to preextinction values over the subsequent 5 million years. These trends imply a factor of 100 increase in the extent of seafloor anoxia and suggest the presence of a shallow oxygen minimum zone (OMZ) that inhibited the recovery of benthic animal diversity and marine ecosystem function. We hypothesize that in the Early Triassic oceans-characterized by prolonged shallow anoxia that may have impinged onto continental shelvesglobal biogeochemical cycles and marine ecosystem structure became more sensitive to variation in the position of the OMZ. Under this hypothesis, the Middle Triassic decline in bottom water anoxia, stabilization of biogeochemical cycles, and diversification of marine animals together reflect the development of a deeper and less extensive OMZ, which regulated Earth system recovery following the end-Permian catastrophe.paleoredox | uranium isotopes | biogeochemical cycling | carbon isotopes | Early TriassicT he end-Permian mass extinction-the most severe biotic crisis in the history of animal life-was followed by 5 million years of reduced biodiversity (1, 2), limited ecosystem complexity (3), and large perturbations in global biogeochemical cycling (4, 5). Ocean anoxia has long been invoked both as a cause of the extinction (6-8) and as a barrier to rediversification (9). Numerous lines of evidence demonstrate widespread anoxic conditions around the time of the end-Permian mass extinction (e.g., refs. 6 and 10-12). In contrast, the prevalence of anoxia during the 5-to 10-millionyear recovery interval remains poorly constrained (13,14).Reconstructing paleoredox conditions is challenging because some indicators of anoxia characterize only the local conditions of the overlying water column, whereas other indicators may be influenced by confounding factors, such as weathering rates on land. Here, we use paired measurements of [U] and δ 238 U in marine carbonate rocks to differentiate changes in weathering of U from variations in global marine redox conditions. Microbially mediated reduction of U(VI) to U(IV) under anoxic conditions at the sediment−water interface results in a substantial decrease in uranium solubility and a measureable change in 238 U/ 235 U (15-18). Because 238 U is preferentially reduced and immobilized relative to 235 U, the δ 238 U value of seawater U(VI) decreases as the areal extent of bottom water anoxia increases (Fig. S1). Consequently, a global increase in the extent of anoxi...

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Section: Methodsmentioning

confidence: 99%

Marine anoxia and delayed Earth system recovery after the end-Permian extinction

Lau

Maher

Altıner

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

240

193

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“…We used CrunchFlow (Maher et al, 2006) to forward model weathering rinds from Costa Rica, Svalbard, and Humphrey (Fig. 4) in one dimension using laboratory rates and diffusivities (Appendix 1).…”

Section: Reactive Transport Modelingmentioning

confidence: 99%

Basalt weathering rates on Earth and the duration of liquid water on the plains of Gusev Crater, Mars

Hausrath

Navarre‐Sitchler

Sak

et al. 2008

Geol

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116

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Where Martian rocks have been exposed to liquid water, chemistry versus depth profiles could elucidate both Martian climate history and potential for life. The persistence of primary minerals in weathered profiles constrains the exposure time to liquid water: on Earth, mineral persistence times range from ~10 ka (olivine) to ~250 ka (glass) to ~1Ma (pyroxene) to ~5Ma (plagioclase). Such persistence times suggest mineral persistence minima on Mars. However, Martian solutions may have been more acidic than on Earth. Relative mineral weathering rates observed for basalt in Svalbard (Norway) and Costa Rica demonstrate that laboratory pH trends can be used to estimate exposure to liquid water both qualitatively (mineral absence or presence) and quantitatively (using reactive transport models). Qualitatively, if the Martian solution pH > ~2, glass should persist longer than olivine; therefore, persistence of glass may be a pHindicator. With evidence for the pH of weathering, the reactive transport code CrunchFlow can quantitatively calculate the minimum duration of exposure to liquid water consistent with a chemical profile. For the profile measured on the surface of Humphrey in Gusev Crater, the minimum exposure time is 22 ka. If correct, this estimate is consistent with short-term, episodic alteration accompanied by ongoing surface erosion. More of these depth profiles should be measured to illuminate the weathering history of Mars.

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“…Mineral precipitation in the KμC model is handled in a similar fashion to the way it is usually treated in the CrunchFlow code based on either irreversible or TST-type rate laws (Lasaga, 1981;1984;Aagaard and Helgeson, 1982;Maher et al, 2006;Maher et al, 2009):…”

Section: Mineral Precipitationmentioning

confidence: 99%

“…Although these weathering rates cannot be probed directly, laboratory-scale weathering experiments (Ferrand et al, 2006;Icenhower et al, 2008;Cailleteau et al, 2011) and geochemical reconstructions (Maher et al, 2006) suggest that they are several orders of magnitude lower than the readily accessible short-term weathering rates of pristine silicate surfaces. Predictive models of these millennial-scale rates remain poorly constrained, and even the fundamental physical processes that cause their age-dependence have not been unambiguously identified (Casey, 2008;Frugier et al, 2008;Icenhower et al, 2008).…”

Section: Introductionmentioning

confidence: 97%

Progress toward bridging from atomistic to continuum modeling to predict nuclear waste glass dissolution.

Zapol

Bourg

Criscenti³

et al. 2011

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This report summarizes research performed for the Nuclear Energy Advanced Modeling and Simulation (NEAMS) Subcontinuum and Upscaling Task. The work conducted focused on developing a roadmap to include molecular scale, mechanistic information in continuum-scale models of nuclear waste glass dissolution. This information is derived from molecular-scale modeling efforts that are validated through comparison with experimental data. In addition to developing a master plan to incorporate a subcontinuum mechanistic understanding of glass dissolution into continuum models, methods were developed to generate constitutive dissolution rate expressions from quantum calculations, force field models were selected to generate multicomponent glass structures and gel layers, classical molecular modeling was used to study diffusion through nanopores analogous to those in the interfacial gel layer, and a micro-continuum model (KµC) was developed to study coupled diffusion and reaction at the glass-gel-solution interface. We would also like to acknowledge discussions with the International Corrosion Working Group members including Stéphane Gin,

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The mineral dissolution rate conundrum: Insights from reactive transport modeling of U isotopes and pore fluid chemistry in marine sediments

Cited by 241 publications

References 100 publications

Marine anoxia and delayed Earth system recovery after the end-Permian extinction

Marine anoxia and delayed Earth system recovery after the end-Permian extinction

Basalt weathering rates on Earth and the duration of liquid water on the plains of Gusev Crater, Mars

Progress toward bridging from atomistic to continuum modeling to predict nuclear waste glass dissolution.

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