Equilibrium Cu isotope fractionation in copper minerals: a first-principles study

Liu, Shanqi; Li, Yongbing; Liu, Jie; Yang, Zhiming; Liu, Jianming; Shi, Yaolin

doi:10.1016/j.chemgeo.2021.120060

Cited by 23 publications

(16 citation statements)

References 157 publications

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“…However, coordination data and bond lengths obtained from EXAFS analyses can correlate with the final Cu isotope composition (Pokrovsky et al, 2008). The adsorption of Cu onto various inorganic surfaces results in different changes of bond lengths and/or "stiffness" of bonds, and it can be speculated that, consequently, in different extents of isotope fractionation, i.e., 1.85-2.05 Å for goethite, hematite, lepidocrocite, boehmite, kaolinite, quartz (e.g., Boudesocque et al, 2007;Lin et al, 2004;Parkman et al, 1999;Peacock & Sherman, 2005;Weesner & Bleam, 1997), which is in accordance with the average calculated and measured Cu-O bond lengths in various Cu minerals (1.88-2.03 Å and 1.85-1.99 Å, respectively; Liu et al, 2021).…”

Section: Cu Complexationsupporting

confidence: 84%

Metal isotope complexation with environmentally relevant surfaces: Opening the isotope fractionation black box

Komárek

Ratié

Vaňková

et al. 2021

Critical Reviews in Environmental Science and Technology

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The number of studies using various stable isotope systems for tracing contamination sources and various biogeochemical processes is rapidly rising due to the increased availability of the techniques used for isotope analyses. However, in most cases, the resulting isotope data are influenced by many processes occurring within reactive environmental compartments, e.g., soils and sediments, such as sorption, precipitation, redox changes, interactions with plants and microorganisms, etc. Therefore, isotope tracing becomes challenging as it is crucial to identify and quantify the isotope fractionation extent during separate processes in this so-called "isotope fractionation black box". The main aim of this review is to (i) summarize literature data on fractionation of selected metal isotopes (Cd, Cu, Hg, Ni, Zn) after complexation with relevant environmental surfaces, e.g., oxyhydroxides, clay minerals, natural organic matter etc., (ii) briefly describe the analytical techniques and key procedures used for the determination of such data and (iii) provide suggestions and perspectives for future research, including a critical evaluation of specific issues related to isotope analyses and especially the interpretation of results. For example, concentration equilibrium usually differs from isotope fractionation equilibrium, metal coordination chemistry in solution is crucial to decipher metal isotopic fractionation, spectroscopic data are missing, different experimental conditions are often and potential precipitation and desorption reactions are not always considered, etc. Consistent presentation of adsorption/complexation data would also be highly beneficial in future studies.

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Section: Cu Complexationsupporting

confidence: 84%

Metal isotope complexation with environmentally relevant surfaces: Opening the isotope fractionation black box

Komárek

Ratié

Vaňková

et al. 2021

Critical Reviews in Environmental Science and Technology

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“…We adopt a force constant of 54 ± 27 N m −1 for Cu in silicate melt, with the caveat that a slightly higher force constant might be expected in natural samples given our overestimate of the bond length, but we expect the true value to be within the error of the value given here. Liu et al (2021) calculated the β-factors of a variety of Cu-bearing minerals. For Cu + -bearing minerals, they reported force constants between 54 and 135 N m −1 , but all those minerals are either sulfides or oxides.…”

Section: Coppermentioning

confidence: 99%

The Extent, Nature, and Origin of K and Rb Depletions and Isotopic Fractionations in Earth, the Moon, and Other Planetary Bodies

Dauphas¹,

Nie²,

Blanchard³

et al. 2022

Planet. Sci. J.

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Moderately volatile elements (MVEs) are depleted and isotopically fractionated in the Moon relative to Earth. To understand how the composition of the Moon was established, we calculate the equilibrium and kinetic isotopic fractionation factors associated with evaporation and condensation processes. We also reassess the levels of depletions of K and Rb in planetary bodies. Highly incompatible element ratios are often assumed to be minimally affected by magmatic processes, but we show that this view is not fully warranted, and we develop approaches to mitigate this issue. The K/U weight ratios of Earth and the Moon are estimated to be 9704 and 2448, respectively. The 87Rb/86Sr atomic ratios of Earth and the Moon are estimated to be 0.072 5 and 0.015 4, respectively. We show that the depletions and heavy isotopic compositions of most MVEs in the Moon are best explained by evaporation in 99%-saturated vapor. At 99% saturation in the protolunar disk, Na and K would have been depleted to levels like those encountered in the Moon on timescales of ∼40–400 days at 3500–4500 K, which agrees with model expectations. In contrast, at the same saturation but a temperature of 1600–1800 K relevant to hydrodynamic escape from the lunar magma ocean, Na and K depletions would have taken 0.1–103 Myr, which far exceeds the 1000 yr time span until plagioclase flotation hinders evaporation from the magma ocean. We conclude that the protolunar disk is a much more likely setting for the depletion of MVEs than the lunar magma ocean.

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“…When the most common valence state of Cu hosted by sulfide in basaltic rocks is Cu + (e.g., Lee et al., 2012), oxidizing Cu + to Cu 2+ during sulfide dissolution could release isotopically heavy Cu to fluids, leaving the altered basalts isotopically lighter than the primary basalts. This has been verified by laboratory experiments and first‐principles calculation (Fernandez & Borrok, 2009; S. Liu et al., 2021; Mathur et al., 2005; Wang et al., 2021). Copper oxidation during sulfide dissolution could therefore account for the lower Cu content and isotopic values at the altered rims than in the core (J. Huang et al., 2016), also consistent with the lower sulfide content in the altered rims than in the core (Figure 3c).…”

Section: Discussionmentioning

confidence: 67%

“…As alteration proceeds, a concentration gradient between the edges and the interior of the basalt possibly resulted in concentration‐driven diffusion in the basalt. The oxidation of Cu + to Cu 2+ during sulfide dissolution, as mentioned above, prefers to release isotopically heavy Cu to fluids (Fernandez & Borrok, 2009; J. Huang et al., 2016; S. Liu et al., 2021; Mathur et al., 2005), thereby altering the edges of basalt and decreasing δ 65 Cu values there. The decreasing δ 65 Cu values with low Cu contents were previously reported in altered oceanic crust at Integrated Ocean Drilling Program Site 1,256 (J. Huang et al., 2016) and Alpine oceanic metagabbros (Busigny et al., 2018), and attributed to the oxidative breakdown of sulfide on the seafloor.…”

Section: Discussionmentioning

confidence: 99%

Copper Isotopic Fractionation During Seafloor Alteration: Insights From Altered Basalts in the Mariana and Yap Trenches

Guo

Tian

Liu³

et al. 2022

JGR Solid Earth

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To further investigate copper (Cu) isotopic fractionation during seawater‐oceanic crust interactions, 13 subsamples across a basalt altering section and 12 bulk‐rock basalts from the southern Mariana and Yap trenches, western Pacific Ocean, were studied. We find that the δ65Cu values of the basalt section roughly increase from mid‐ocean ridge basalt‐like values (0.04% – 0.10%) in the core to higher values (up to 0.20%) near the core‐rim interface, and then lower values (down to −0.17%) at the rims. Isotopically light rims reflect the initial dissolution of Cu‐bearing sulfides releasing isotopically heavy Cu into ambient seawater, consistent with both lower Cu and sulfide contents in the altered rims. The elevated δ65Cu values reveal that sulfide dissolution induced a concentration‐driven diffusion from the core to rims, controlling the rim‐core‐rim Cu content and isotopic variations on centimeter scale. By contrast, the δ65Cu values of bulk‐rock basalts show a wide range (0.02% – 0.56%) with most samples enriched in heavy isotopes, and negatively correlate with Cu concentrations, indicating preferential adsorption of isotopically heavy Cu from seawater. We propose that chemical diffusion occurred prior to any adsorption processes, suggesting that a three‐stage process involving sulfide dissolution, chemical diffusion and adsorption controls Cu isotopic fractionation during seafloor basalt alteration.

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Equilibrium Cu isotope fractionation in copper minerals: a first-principles study

Cited by 23 publications

References 157 publications

Metal isotope complexation with environmentally relevant surfaces: Opening the isotope fractionation black box

Metal isotope complexation with environmentally relevant surfaces: Opening the isotope fractionation black box

The Extent, Nature, and Origin of K and Rb Depletions and Isotopic Fractionations in Earth, the Moon, and Other Planetary Bodies

Copper Isotopic Fractionation During Seafloor Alteration: Insights From Altered Basalts in the Mariana and Yap Trenches

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