scholarly journals Iron Isotope Compositions of Coexisting Sulfide and Silicate Minerals in Sudbury-Type Ores from the Jinchuan Ni-Cu Sulfide Deposit: A Perspective on Possible Core-Mantle Iron Isotope Fractionation

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 464
Author(s):  
Peiyao Wang ◽  
Yaoling Niu ◽  
Pu Sun ◽  
Xiaohong Wang ◽  
Pengyuan Guo ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Isotope Composition ◽  
Sulfide Minerals ◽  
Sulfide Deposit ◽  
Sulfide Liquid ◽  
Silicate Liquid ◽  
Iron Isotope ◽  
Weighted Mean ◽  
Silicate Minerals ◽  
The Core

Many studies have shown that the average iron (Fe) isotope compositions of mantle-derived rocks, mantle peridotite and model mantle are close to those of chondrites. Therefore, it is considered that chondrite values represent the bulk Earth Fe isotope composition. However, this is a brave assumption because nearly 90% of Fe of the Earth is in the core, where its Fe isotope composition is unknown, but it is required to construct bulk Earth Fe isotope composition. We approach the problem by assuming that the Earth’s core separation can be approximated in terms of the Sudbury-type Ni-Cu sulfide mineralization, where sulfide-saturated mafic magmas segregate into immiscible sulfide liquid and silicate liquid. Their density/buoyancy controlled stratification and solidification produced net-textured ores above massive ores and below disseminated ores. The coexisting sulfide minerals (pyrrhotite (Po) > pentlandite (Pn) > chalcopyrite (Cp)) and silicate minerals (olivine (Ol) > orthopyroxene (Opx) > clinopyroxene (Cpx)) are expected to hold messages on Fe isotope fractionation between the two liquids before their solidification. We studied the net-textured ores of the Sudbury-type Jinchuan Ni-Cu sulfide deposit. The sulfide minerals show varying δ56Fe values (−1.37–−0.74‰ (Po) < 0.09–0.56‰ (Cp) < 0.53–1.05‰ (Pn)), but silicate minerals (Ol, Opx, and Cpx) have δ56Fe values close to chondrites (δ56Fe = −0.01 ± 0.01‰). The heavy δ56Fe value (0.52–0.60‰) of serpentines may reflect Fe isotopes exchange with the coexisting pyrrhotite with light δ56Fe. We obtained an equilibrium fractionation factor of Δ56Fesilicate-sulfide ≈ 0.51‰ between reconstructed silicate liquid (δ56Fe ≈ 0.21‰) and sulfide liquid (δ56Fe ≈ −0.30‰), or Δ56Fesilicate-sulfide ≈ 0.36‰ between the weighted mean bulk-silicate minerals (δ56Fe[0.70ol,0.25opx,0.05cpx] = 0.06‰) with weighted mean bulk-sulfide minerals (δ56Fe ≈ −0.30‰). Our study indicates that significant Fe isotope fractionation does take place between silicate and sulfide liquids during the Sudbury-type sulfide mineralization. We hypothesize that significant iron isotope fractionation must have taken place during core–mantle segregation, and the bulk Earth may have lighter Fe isotope composition than chondrites although Fe isotope analysis on experimental sulfide-silicate liquids produced under the varying mantle depth conditions is needed to test our results. We advocate the importance of further research on the subject. Given the close Fe-Ni association in the magmatic mineralization and the majority of the Earth’s Ni is also in the core, we infer that Ni isotope fractionation must also have taken place during the core separation that needs attention.

scholarly journals Iron isotope fractionation at the core–mantle boundary by thermodiffusion

2020 ◽  
Vol 13 (5) ◽  
pp. 382-386 ◽  
Author(s):  
Charles E. Lesher ◽  
Juliane Dannberg ◽  
Gry H. Barfod ◽  
Neil R. Bennett ◽  
Justin J. G. Glessner ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Iron Isotope ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core

New potential pyrrhotite and pentlandite reference materials for sulfur and iron isotope microanalysis

2021 ◽  
Author(s):  
Lei Chen ◽  
Yu Liu ◽  
Yang Li ◽  
Qiuli Li ◽  
Xian-Hua Li
Keyword(s):  
Reference Materials ◽  
Sulfide Minerals ◽  
Ore Deposits ◽  
Iron Isotope ◽  
S Isotopes ◽  
Fe Isotopes

Pyrrhotite and pentlandite are the most common Fe sulfide minerals in magmatic ore deposits and meteorites. Multiple S isotopes pairing with Fe isotopes of bulk Fe sulfides have proven to...

A sulfide perspective on iron isotope fractionation during ocean island basalt petrogenesis

2019 ◽  
Vol 245 ◽  
pp. 59-78 ◽  
Author(s):  
Bradley J. Peters ◽  
Anat Shahar ◽  
Richard W. Carlson ◽  
James M.D. Day ◽  
Timothy D. Mock
Keyword(s):  
Isotope Fractionation ◽  
Ocean Island Basalt ◽  
Iron Isotope ◽  
Ocean Island ◽  
Island Basalt

scholarly journals Chlorine isotope composition in chlorofluorocarbons CFC-11, CFC-12 and CFC-113 in firn, stratospheric and tropospheric air

2015 ◽  
Vol 15 (12) ◽  
pp. 6867-6877 ◽  
Author(s):  
S. J. Allin ◽  
J. C. Laube ◽  
E. Witrant ◽  
J. Kaiser ◽  
E. McKenna ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Isotope Composition ◽  
Stratospheric Ozone ◽  
Standard Uncertainty ◽  
Gas Chromatography Mass Spectrometry ◽  
Sources And Sinks ◽  
Chlorine Isotope ◽  
Tropospheric Measurements ◽  
Single Detector

Abstract. The stratospheric degradation of chlorofluorocarbons (CFCs) releases chlorine, which is a major contributor to the destruction of stratospheric ozone (O3). A recent study reported strong chlorine isotope fractionation during the breakdown of the most abundant CFC (CFC-12, CCl2F2, Laube et al., 2010a), similar to effects seen in nitrous oxide (N2O). Using air archives to obtain a long-term record of chlorine isotope ratios in CFCs could help to identify and quantify their sources and sinks. We analyse the three most abundant CFCs and show that CFC-11 (CCl3F) and CFC-113 (CClF2CCl2F) exhibit significant stratospheric chlorine isotope fractionation, in common with CFC-12. The apparent isotope fractionation (&amp;varepsilon;app) for mid- and high-latitude stratospheric samples are respectively −2.4 (0.5) and −2.3 (0.4) ‰ for CFC-11, −12.2 (1.6) and −6.8 (0.8) ‰ for CFC-12 and −3.5 (1.5) and −3.3 (1.2) ‰ for CFC-113, where the number in parentheses is the numerical value of the standard uncertainty expressed in per mil. Assuming a constant isotope composition of emissions, we calculate the expected trends in the tropospheric isotope signature of these gases based on their stratospheric 37Cl enrichment and stratosphere–troposphere exchange. We compare these projections to the long-term δ (37Cl) trends of all three CFCs, measured on background tropospheric samples from the Cape Grim air archive (Tasmania, 1978–2010) and tropospheric firn air samples from Greenland (North Greenland Eemian Ice Drilling (NEEM) site) and Antarctica (Fletcher Promontory site). From 1970 to the present day, projected trends agree with tropospheric measurements, suggesting that within analytical uncertainties, a constant average emission isotope delta (δ) is a compatible scenario. The measurement uncertainty is too high to determine whether the average emission isotope δ has been affected by changes in CFC manufacturing processes or not. Our study increases the suite of trace gases amenable to direct isotope ratio measurements in small air volumes (approximately 200 mL), using a single-detector gas chromatography–mass spectrometry (GC–MS) system.

scholarly journals Chlorine isotope composition in chlorofluorocarbons CFC-11, CFC-12 and CFC-113 in firn, stratospheric and tropospheric air

2014 ◽  
Vol 14 (23) ◽  
pp. 31813-31841
Author(s):  
S. J. Allin ◽  
J. C. Laube ◽  
E. Witrant ◽  
J. Kaiser ◽  
E. McKenna ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Isotope Composition ◽  
Stratospheric Ozone ◽  
Isotope Ratios ◽  
Gas Chromatography Mass Spectrometry ◽  
Chlorine Isotope ◽  
Site Model ◽  
Tropospheric Measurements ◽  
Single Detector

Abstract. The stratospheric degradation of chlorofluorocarbons (CFCs) releases chlorine, which is a major contributor to the destruction of stratospheric ozone (O3). A recent study reported strong chlorine isotope fractionation during the breakdown of the most abundant CFC (CFC-12, CCl2F2), similar to effects seen in nitrous oxide (N2O). Using air archives to obtain a long-term record of chlorine isotope ratios in CFCs could help to identify and quantify their sources and sinks. We analyse the three most abundant CFCs and show that CFC-11 (CCl3F) and CFC-113 (CClF2CCl2F) exhibit significant stratospheric chlorine isotope fractionation, in common with CFC-12. The apparent isotope fractionation (&amp;varepsilon;app) for mid- and high-latitude stratospheric samples are (−2.4 ± 0.5) and (−2.3 ± 0.4)‰ for CFC-11, (−12.2 ± 1.6) and (−6.8 ± 0.8)‰ for CFC-12 and (−3.5 ± 1.5) and (−3.3 ± 1.2)‰ for CFC-113, respectively. Assuming a constant source isotope composition, we estimate the expected trends in the tropospheric isotope signature of these gases due to their stratospheric 37Cl enrichment and stratosphere–troposphere exchange. We compare these model results to the long-term δ(37Cl) trends of all three CFCs, measured on background tropospheric samples from the Cape Grim air archive (Tasmania, 1978–2010) and tropospheric firn air samples from Greenland (NEEM site) and Antarctica (Fletcher Promontory site). Model trends agree with tropospheric measurements within analytical uncertainties. From 1970 to the present-day, we find no evidence for variations in chlorine isotope ratios associated with changes in CFC manufacturing processes. Our study increases the suite of trace gases amenable to direct isotope ratio measurements in small air volumes, using a single-detector gas chromatography-mass spectrometry system.

scholarly journals Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria

2010 ◽  
Vol 74 (10) ◽  
pp. 2826-2842 ◽  
Author(s):  
A. Kappler ◽  
C.M. Johnson ◽  
H.A. Crosby ◽  
B.L. Beard ◽  
D.K. Newman
Keyword(s):  
Isotope Fractionation ◽  
Iron Isotope

An experimental study of carbon-isotope fractionation between diet, hair, and feces of mammalian herbivores

2003 ◽  
Vol 81 (5) ◽  
pp. 871-876 ◽  
Author(s):  
Matt Sponheimer ◽  
Todd Robinson ◽  
Linda Ayliffe ◽  
Ben Passey ◽  
Beverly Roeder ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Fractionation ◽  
Cynodon Dactylon ◽  
Isotope Composition ◽  
Mammalian Herbivores ◽  
Carbon Isotope Fractionation ◽  
Tropical Environments ◽  
The Mean ◽  
Lama Pacos

The carbon-isotope composition of hair and feces offers a glimpse into the diets of mammalian herbivores. It is particularly useful for determining the relative consumption of browse and graze in tropical environments, as these foods have strongly divergent carbon-isotope compositions. Fecal δ13C values reflect the last few days consumption, whereas hair provides longer term dietary information. Previous studies have shown, however, that some fractionation occurs between dietary δ13C values and those of hair and feces. Accurate dietary reconstruction requires an understanding of these fractionations, but few controlled-feeding studies have been undertaken to investigate these fractionations in any mammalian taxa, fewer still in large mammalian herbivores. Here, we present data from the first study of carbon-isotope fractionation between diet, hair, and feces in multiple herbivore taxa. All taxa were fed pure alfalfa (Medicago sativa) diets for a minimum period of 6 months, at which point recently grown hair was shaved and analyzed for carbon isotopes. The mean observed diet–hair fractionation was +3.2‰, with a range of +2.7 to +3.5‰. We also examined diet–feces fractionation for herbivores on alfalfa and bermudagrass (Cynodon dactylon) feeds. The mean diet–feces fractionation for both diets was –0.8‰, with less fractionation for alfalfa (–0.6‰) than bermudagrass (–1.0‰). Fecal carbon turnover also varies greatly between taxa. When diets were switched, horse (Equus caballus) feces reflected the new diet within 60 h, but alpaca (Lama pacos) feces did not equilibrate with the new diet for nearly 200 h. Thus, fecal carbon isotopes provide far greater dietary resolution for hindgut-fermenting horses than foregut-fermenting alpacas.

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