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
Abstract
:1. Introduction
- (1)
- The core separation was accomplished through silicate melt and sulfide melt segregation due to density difference. The sulfide melt must have then developed into the Fe-Ni metallic core through sulfur removal under core depth pressure-temperature conditions. Hence the prior sulfides and metals must possess the same iron isotope composition, representing that of the metallic core in equilibrium with the silicate Earth (Figure 1).
- (2)
- The core–mantle separation took place under high pressure and temperature in the deep Earth, but the magmatism takes place under upper mantle or deep crustal conditions. We do not ignore the effects of pressure and temperature on potential Fe isotope fractionation, but we use the best natural materials to study this important problem as the strategically must-do first step. The results will form the foundation for further studies.
2. Geological Setting
3. Sample and Methods
3.1. Sample
3.2. Methods
4. Results
4.1. Mineral Chemistry
4.2. Bulk-Rock Ore Sample Major Element Composition
4.3. Iron Isotopes of Mineral Separates
5. Discussion
- (1)
- A sulfur-rich and sulfide saturated mafic magma led to sulfide melt exsolution/segregation, forming a system of coexisting two-phase liquids, the silicate liquid and the sulfide liquid.
- (2)
- (3)
- With the higher liquidus temperature, mafic silicate minerals (olivine, orthopyroxene, and clinopyroxene) with densities of 3.25–3.35 g cm−3 [52] begin to crystallize first and tend to sink at the base of the silicate liquid, but would suspend in the denser sulfide liquid, constituting the network texture.
- (4)
- Subsequent crystallization of sulfide liquid and solidification of the system results in the observed net-textured Ni-Cu ores above the massive ores and below the disseminated ores in this density/buoyancy controlled scenario.
5.1. Iron Isotope Composition of Different Iron-Bearing Minerals
5.1.1. Iron Isotope Compositional Differences between Minerals with Different Valence States
5.1.2. Iron Isotope Compositional Differences between Coexisting Sulfide Minerals
5.1.3. Iron Isotope Compositions of Primary Silicate Minerals
5.1.4. Iron Isotope Compositions of Serpentines
5.2. Constructing Iron Isotope Compositions of Coexisting Sulfide Liquid and Silicate Liquid
5.2.1. Iron Isotope Compositions of the Silicate Liquid
5.2.2. Iron Isotope Compositions of the Sulfide Liquid
- (1)
- By excluding the gains of light Fe isotopes for pyrrhotite caused by serpentinization. The δ56Fe values of the bulk-sulfide of JC-1 and JC-2 would be −0.77‰ and −0.20‰, respectively.
- (2)
- By using pyrrhotite that is less affected by serpentinization in sample JC-3 instead the pyrrhotite in JC-1 and 2, which are strongly serpentinized, the δ56Fe values of the bulk-sulfide of JC-1 and JC-2 would be −0.39‰ and −0.22‰, respectively.
- (3)
- By taking full consideration of the probable gains of light Fe isotopes for pyrrhotite caused by serpentinization, we could use the difference of iron isotope compositions between the serpentine and average of unaltered silicate minerals (δ56Fe = 0.05‰, Ol, Cpx, and Opx) in the net-textured ores, the iron contents of serpentine and pyrrhotite, and the contents of these two minerals in the whole ore respectively to calculate how much lighter are Fe isotope compositions of the pyrrhotite caused by serpentinization as Δ56FePo × WPo × FePo = Δ56FeSerp-Ol × WSerp × FeSerp (WPo = Po content in ore; FePo = iron content in Po; Wserp = Serp content in ore; Feserp% = iron content in Serp), then take the analytical value plus the Δ56FePo calculated above to give the probable value of pyrrhotite before serpentinization as δ56FePo-before serpentinized = δ56FePo-analytical value + Δ56FePo. The δ56Fe values of the bulk-sulfide of JC-1 and JC-2 would be −0.59‰ and −0.11‰, respectively.
- (4)
- If we use pentlandite and chalcopyrite only without including pyrrhotite modified by later serpentinization, we would obtain δ56Fe values of the bulk-sulfide of JC-1 and JC-2 to be 0.32‰ and 0.95‰, respectively.
5.2.3. Differences of Iron Isotopes Between Sulfide Liquid and Silicate Liquid
6. Conclusions
- (1)
- There were three major sulfide minerals (pyrrhotite (Po), chalcopyrite (Cp), and pentlandite (Pn)) in the net-textured ores. The δ56Fe value of these sulfides varied greatly: −1.37–−0.74‰ (Po) < 0.09–0.56‰ (Cp) < 0.53–1.05‰ (Pn).
- (2)
- The silicate minerals were all of cumulate origin, dominated by olivine (Ol) with a small amount of pyroxene (clinopyroxene (Cpx) < orthopyroxene (Opx)). Their δ56Fe values were 0.07 ± 0.03‰ (Ol) > 0.05 ± 0.07‰ (Opx) > 0.04 ± 0.02‰ (Cpx), which were all close to the chondritic values.
- (3)
- By assuming that the coexisting sulfide and silicate minerals of net-textured ores were crystallized/solidified from respective sulfide and silicate liquids segregated from the sulfur-rich and sulfide-saturated parental magma, and by reconstructing the weighted mean iron isotope compositions of bulk-sulfide minerals and bulk-silicate minerals, we obtained the iron isotope composition of the silicate liquid (δ56Fe ≈ 0.21‰) in equilibrium with the silicate minerals (Ol, Cpx, and Opx) and the iron isotope composition of the sulfide liquid (δ56Fe ≈ −0.30‰), which was the best value possible with caveats, including the effect of serpentinization that must have resulted in heavy Fe isotope enrichment in serpentines while light Fe isotope enrichment in the coexisting pyrrhotite.
- (4)
- Our preferred scenario of core formation was through silicate-sulfide liquid segregation followed by sulfur removal. The sulfide liquid iron isotope composition was expected to be the same as the metallic core. Thus, there must be iron isotope fractionation between the metallic core and the silicate mantle according to the significant differences of iron isotope composition between the sulfide liquid and silicate liquid obtained from the Jinchuan net-textured sulfide ore samples with the fractionation factor of Δ56Fesilicate-sulfide ≈ 0.51‰. If we simply compared the difference between the weighted mean bulk-silicate minerals of δ56Fe(0.70ol,0.25opx,0.05cpx) = 0.06‰ with weighted mean bulk-sulfide minerals of δ56Fe ≈ −0.30‰, we would have Δ56Fesilicate-sulfide ≈ 0.36‰. This is still a rather large difference and we do not intend to claim this value to be correct, but emphasize that iron isotope fractionation does take place between silicates and sulfides in the Sudbury-type magmatic sulfide mineralization. We thus hypothesized that iron isotope fractionation must take place during core–mantle separation, and predicted that the bulk Earth must have significantly lighter Fe isotope composition than the chondrites (i.e., δ56Fe < −0.01 ± 0.01‰). We predicted that the Fe isotope analysis of coexisting sulfide-silicate liquids produced experimentally under varying mantle depth conditions will complement the study of the type we reported here and altogether helped provide credible Fe isotope compositions of the bulk-Earth and the possible Fe isotope differences between the Earth’s core and the silicate Earth.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
Appendix A
- (1)
- The weight percentages of the major elements FeOT, CuO, and NiO in the impure mineral separates (wt.%; Table 4) are converted into the mole percentages of the elements Fe, Cu, and Ni (mol.%);
- (2)
- According to the empirical molecular formulae given by different sulfides in Table 2, the mole percentage of the element is converted into the mineral molecular percentage (mol.%). Assuming that the coefficients of Fe, Cu, and Ni in the empirical molecular formula of sulfide are x, y, and z respectively, the general molecular formula can be expressed as FexCuyNizSn, which gives pyrrhotite as Fex1Cuy1Niz1S, chalcopyrite as Fex2Cuy2Niz2S2, and pentlandite as Fex3Cuy3Niz3S8;Pentlandite (mol.%) = Ni (mol.%)/z3, chalcopyrite (mol.%) = Cu (mol.%)/y2,Fe content of Pyrrhotite (mol.%) = Total Fe − x3 × Pentlandite (mol.%) − x2 × chalcopyrite (mol.%), and Pyrrhotite (mol.%) = Fe content of Pyrrhotite (mol.%)/x1.
- (3)
- The mole percentage of each sulfide and its empirical molecular formula (Table 2) are converted to the mass percentage (wt.%) of each sulfide, and then normalized to 100%. Sulfide (wt.%) = Sulfide (mol.%) × The relative molecular mass of the empirical molecular formula × 100%.
Appendix B
Appendix C
- (1)
- The major ore elements (such as FeO, CuO, and Cr2O3 in wt.%; Table 4) in the bulk-ore samples (JC-1, 2, and 3) are converted to their molar percentages (such as Fe, Cu, and Cr in mol.%).
- (2)
- The modal mineralogy in mol.% can be calculated using the unique element of each mineral (e.g., Ni in pentlandite, Cu in chalcopyrite, Cr in chromite, etc.). For the elements common in all minerals, simultaneous equations are used.
- (3)
- Since pyrrhotite only contains Fe and S, its modal calculation is done after the modes of all other iron-bearing minerals are completed using the residual Fe of total Fe minus all the Fe already used so as to obtain the modes of all the major minerals in the net-textured ore samples.
- (4)
- Then, convert the molar percentage of each mineral in the bulk-ore samples into weight percentage (wt.%) using the molecular formulae (Table 8): Each mineral (wt.%) = each mineral (mol.%) × relative molecular weight in the experimental molecular formula;
- (5)
- Normalize the above to 100%.
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Sample No. | Ore Type | Petrographic Description |
---|---|---|
JC-1 | Net-textured ore | sulfide-rich dunite, composed chiefly of olivine (~8%), which has been completely altered to serpentine (~68%) (olivine + serpentine ≈ 76%). The interstitial space between olivine grains is mainly filled by sulfides (~22%), including pyrrhotite (~12%), chalcopyrite (~4%), and pentlandite (~6%), forming the structure of spongy meteorite (net-texture), minor Cr-spinel (~1%) and altered minerals (~1%). |
JC-2 | Net-textured ore | sulfide-rich dunite, composed chiefly of olivine (~32%), which has been strongly serpentinized (~46%) ((olivine + serpentine ≈ 78%). The interstitial space between olivine grains is mainly filled by sulfides (~18%), including pyrrhotite (~10%), chalcopyrite (~2%), and pentlandite (~6%), forming the structure of spongy meteorite (net-texture), minor Cr-spinel (~1%), and altered minerals (~3%). |
JC-3 | Net-textured ore | sulfide-rich lherzolite, consists of olivine (~50%), pyroxenes (~35%; orthopyroxene (~20%) > clinopyroxene (~15%)), plagioclase (~4%), and minor Cr-spinel (~1%). Metallic sulfides are mainly composed of pyrrhotite (~5%), chalcopyrite (~3%), pentlandite (~2%), and minor cubanite. |
JC-4 | Disseminated ore | sulfide-rich altered ore from metasomatic orebody at the contact of the mafic intrusion with dolomite marble dominated by dolomite (~50%), phlogopite (~16%), amphibole (~12%), sulfide (~16%), and a small amount of serpentine (~6%). |
Sample No. | Ore Type | Sulfide Mineral | Calculated Molecular Formula | N | S | Fe | Cu | Ni | Total |
---|---|---|---|---|---|---|---|---|---|
wt.% | wt.% | wt.% | wt.% | wt.% | |||||
JC-1 | Net-textured ore | Pyrrhotite | Fe0.855S | 36 | 39.86 | 59.37 | 0.044 | 0.092 | 99.53 |
Chalcopyrite | Cu0.944Fe0.959S2 | 32 | 36.20 | 30.23 | 33.85 | 0.051 | 100.5 | ||
Pentlandite | (Fe4.531,Ni3.825)8.355S8 | 25 | 34.51 | 34.04 | 0.051 | 30.20 | 99.31 | ||
JC-2 | Net-textured ore | Pyrrhotite | Fe0.852S | 26 | 40.42 | 60.01 | 0.052 | 0.202 | 100.8 |
Chalcopyrite | Cu0.912Fe0.930S2 | 13 | 36.62 | 29.65 | 33.09 | 0.018 | 99.57 | ||
Pentlandite | (Fe4.125,Ni4.038)8.164S8 | 22 | 34.15 | 30.67 | 0.087 | 31.56 | 97.31 | ||
JC-3 | Net-textured ore | Pyrrhotite | Fe0.889S | 15 | 39.74 | 61.53 | 0.059 | 0.044 | 101.5 |
Chalcopyrite | Cu0.885Fe0.948S2 | 18 | 36.79 | 30.36 | 32.27 | 0.011 | 99.60 | ||
Pentlandite | (Fe4.026,Ni3.507)7.533S8 | 13 | 36.31 | 31.83 | 0.249 | 29.14 | 98.35 | ||
Cubanite | Cu0.857Fe1.849S3 | 5 | 37.94 | 40.71 | 21.47 | 0.022 | 100.3 | ||
JC-4 | Disseminated ore | Pyrrhotite | Fe0.826S | 13 | 41.38 | 59.51 | 0.051 | 0.492 | 101.6 |
Chalcopyrite | Cu0.897Fe0.937S2 | 8 | 36.95 | 30.16 | 32.85 | 0.081 | 100.3 | ||
Pentlandite | (Fe3.997,Ni3.930)7.928S8 | 12 | 35.45 | 30.85 | 0.064 | 31.88 | 99.00 |
Sample No. | Standard | JC-1 | JC-2 | JC-3 | JC-4 | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mineral | BIR-1G | BCR-2G | BHVO-2G | Olivine | Serpentine | Chromite | Olivine | Serpentine | Chromite | Olivine | Serpentine | Chromite | Clinopyroxene | Orthopyroxene | Plagioclase | Serpentine |
N | 24 | 24 | 24 | 4 | 3 | 12 | 4 | 4 | 9 | 3 | 3 | 7 | 4 | 4 | 2 | 8 |
Major elements (wt.%) | ||||||||||||||||
SiO2 | 46.84 | 53.02 | 49.01 | 38.19 | 36.12 | 0.052 | 38.80 | 38.75 | 0.081 | 38.54 | 38.71 | 0.058 | 50.18 | 53.69 | 53.38 | 39.97 |
TiO2 | 0.929 | 2.254 | 2.698 | 0.017 | 0.434 | 0.925 | 0.012 | 0.020 | 1.471 | 0.021 | 0.012 | 1.150 | 0.417 | 0.195 | 0.106 | 0.020 |
Al2O3 | 15.23 | 13.91 | 14.28 | 0.023 | 3.842 | 9.636 | 0.026 | 2.623 | 0.133 | 0.041 | 0.028 | 15.69 | 3.630 | 2.186 | 29.25 | 0.038 |
FeOT | 11.52 | 13.91 | 11.79 | 15.43 | 9.003 | 51.64 | 16.52 | 7.738 | 75.96 | 16.72 | 13.24 | 39.22 | 5.812 | 9.496 | 0.418 | 14.68 |
MnO | 0.178 | 0.205 | 0.173 | 0.203 | 0.712 | 0.389 | 0.303 | 0.086 | 0.394 | 0.229 | 0.251 | 0.322 | 0.155 | 0.206 | 0.004 | 0.052 |
MgO | 9.371 | 3.501 | 7.011 | 45.17 | 34.93 | 3.163 | 43.22 | 37.01 | 0.630 | 43.57 | 33.14 | 4.938 | 18.84 | 30.94 | 0.130 | 31.25 |
CaO | 13.12 | 7.108 | 11.33 | 0.141 | 0.042 | 0.033 | 0.387 | 0.009 | 0.014 | 0.126 | 0.371 | 0.014 | 19.27 | 2.220 | 11.47 | 0.164 |
Na2O | 1.862 | 3.218 | 2.284 | 0.006 | 0.018 | 0.068 | 0.026 | 0.004 | 0.137 | 0.003 | 0.027 | 0.123 | 0.298 | 0.049 | 4.804 | 0.059 |
K2O | 0.021 | 1.748 | 0.522 | - | 0.009 | 0.017 | 0.014 | 0.004 | 0.027 | 0.001 | 0.014 | 0.021 | - | 0.001 | 0.279 | 0.032 |
P2O5 | 0.051 | 0.356 | 0.278 | 0.038 | 0.019 | 0.030 | 0.037 | 0.026 | 0.016 | 0.035 | 0.044 | 0.040 | 0.019 | 0.024 | 0.029 | 0.038 |
Cr2O3 | 0.057 | 0.002 | 0.042 | 0.014 | 1.501 | 32.15 | 0.012 | 0.425 | 13.10 | 0.017 | 0.010 | 37.64 | 1.107 | 0.625 | - | 0.055 |
NiO | 0.022 | 0.001 | 0.015 | 0.304 | 0.042 | 0.087 | 0.144 | 0.073 | 0.372 | 0.186 | 0.292 | 0.080 | 0.030 | 0.048 | 0.001 | 0.177 |
FeOcal. | - | - | - | - | - | 28.96 | - | - | 30.46 | - | - | 27.82 | - | - | - | - |
Fe2O3 cal. | - | - | - | - | - | 25.21 | - | - | 50.56 | - | - | 12.67 | - | - | - | - |
Total | 99.30 | 99.36 | 99.52 | 99.53 | 86.73 | 100.7 | 99.51 | 86.77 | 97.40 | 99.49 | 86.14 | 100.6 | 99.81 | 99.71 | 99.88 | 86.55 |
Trace element (ppm) | ||||||||||||||||
Li | 2.922 | 8.934 | 4.573 | 2.745 | 8.089 | 0.463 | 7.076 | 1.434 | 8.287 | 5.396 | 0.184 | 0.622 | 17.08 | 2.492 | 0.205 | 7.453 |
Be | 0.142 | 2.728 | 1.364 | 0.172 | 0.094 | - | 0.136 | 0.103 | 0.283 | 0.018 | 0.129 | 0.100 | 0.025 | 0.038 | 0.612 | 0.063 |
Sc | 42.67 | 33.56 | 32.31 | 4.523 | 72.00 | 1.380 | 2.943 | 13.54 | 1.326 | 5.595 | 4.782 | 1.088 | 64.81 | 29.16 | 0.397 | 18.84 |
V | 534.2 | 704.2 | 441.9 | 3.093 | 291.1 | 9844 | 2.679 | 39.46 | 1096 | 6.076 | 6.303 | 1871 | 275.3 | 120.9 | 2.742 | 7.568 |
Cr | 388.4 | 15.14 | 286.5 | 97.83 | 10272 | - | 79.66 | 2910 | - | 115.7 | 71.10 | - | 7574 | 4273 | 2.000 | 378.8 |
Co | 53.24 | 37.83 | 45.37 | 139.0 | 27.29 | 180.2 | 78.73 | 28.13 | 66.72 | 176.8 | 156.2 | 494.7 | 40.74 | 74.99 | 0.228 | 97.86 |
Ni | 172.5 | 11.64 | 117.5 | 2387 | 329.7 | 683.6 | 1129 | 571.0 | 2919 | 1459 | 2291 | 630.6 | 233.3 | 375.7 | 8.157 | 1395 |
Cu | 120.8 | 16.67 | 129.1 | 0.089 | 2.106 | 14.00 | 0.766 | 0.137 | 0.144 | 0.030 | 470.6 | 0.028 | 0.830 | 0.279 | 0.355 | 71.54 |
Zn | 74.37 | 139.1 | 105.5 | 120.9 | 8.064 | 1577 | 98.60 | 33.43 | 664.8 | 109.1 | 17.14 | 3365 | 29.54 | 73.53 | 2.479 | 59.12 |
Ga | 15.60 | 21.75 | 21.48 | 0.086 | 3.610 | 36.42 | 0.064 | 4.939 | 11.72 | 0.228 | 2.122 | 78.84 | 5.732 | 4.073 | 25.37 | 0.706 |
Ge | 1.132 | 2.363 | 2.763 | 5.037 | 1.300 | - | 5.450 | 1.616 | 1.138 | 1.551 | 2.300 | 0.559 | 3.041 | 11.15 | 2.453 | 2.828 |
Rb | 0.271 | 46.39 | 9.373 | 0.015 | 0.211 | - | 1.013 | 1.548 | - | 0.067 | 0.094 | - | 0.033 | 0.146 | 1.002 | 3.842 |
Sr | 106.8 | 341.7 | 391.0 | 0.014 | 0.624 | 1.879 | 2.044 | 0.228 | 0.804 | 0.188 | 4.305 | 0.006 | 19.27 | 0.506 | 671.9 | 38.59 |
Y | 15.03 | 35.72 | 25.49 | 0.319 | 10.69 | 0.026 | 0.562 | 0.538 | - | 0.454 | 0.686 | 0.005 | 12.31 | 2.121 | 0.401 | 4.087 |
Zr | 13.79 | 182.8 | 165.9 | 0.109 | 11.43 | 0.144 | 0.254 | 0.384 | - | 0.258 | 0.527 | 0.950 | 12.13 | 1.807 | 0.112 | 0.193 |
Nb | 0.511 | 13.49 | 20.40 | 0.003 | 0.058 | 0.040 | 0.230 | 0.223 | 0.066 | 0.001 | 0.011 | 0.098 | 0.023 | 0.005 | 0.015 | 0.415 |
Mo | 0.045 | 237.1 | 3.727 | 0.043 | 0.450 | 0.322 | 0.066 | 0.632 | 0.069 | 0.022 | 0.038 | 0.068 | 0.067 | 0.016 | 0.030 | 7.022 |
Cs | 0.016 | 1.310 | 0.161 | 0.032 | 0.041 | - | 0.237 | 0.364 | - | 0.017 | 0.015 | - | 0.014 | 0.023 | 0.032 | 1.060 |
Ba | 6.594 | 687.4 | 128.7 | 0.021 | 2.643 | 1.605 | 7.628 | 2.537 | 0.809 | 0.107 | 2.652 | - | 0.150 | 0.395 | 233.1 | 12.27 |
La | 0.581 | 25.08 | 14.89 | 0.346 | 1.185 | 0.058 | 0.089 | 0.106 | 0.005 | 0.005 | 0.160 | - | 0.807 | 0.009 | 3.481 | 0.387 |
Ce | 1.810 | 53.02 | 36.73 | 0.002 | 4.515 | 0.084 | 0.267 | 0.238 | 0.037 | 0.008 | 0.353 | - | 3.502 | 0.074 | 6.194 | 1.259 |
Pr | 0.366 | 6.737 | 5.139 | 0.001 | 0.760 | 0.006 | 0.046 | 0.029 | 0.005 | 0.001 | 0.049 | - | 0.709 | 0.013 | 0.617 | 0.213 |
Nd | 2.360 | 28.56 | 24.09 | 0.029 | 4.182 | - | 0.191 | 0.190 | 0.038 | 0.004 | 0.170 | - | 4.462 | 0.137 | 2.300 | 1.125 |
Sm | 1.047 | 6.494 | 6.031 | 0.033 | 1.329 | 0.025 | 0.064 | 0.063 | - | 0.003 | 0.024 | - | 1.742 | 0.074 | 0.304 | 0.399 |
Eu | 0.520 | 2.061 | 2.284 | 0.004 | 0.472 | - | 0.018 | 0.025 | 0.035 | 0.002 | 0.007 | - | 0.517 | 0.034 | 1.039 | 0.126 |
Gd | 1.769 | 6.814 | 6.044 | 0.014 | 1.959 | 0.012 | 0.075 | 0.060 | 0.085 | 0.009 | 0.022 | - | 2.186 | 0.174 | 0.299 | 0.502 |
Tb | 0.360 | 1.161 | 1.083 | 0.004 | 0.308 | - | 0.013 | 0.007 | 0.008 | 0.002 | 0.007 | - | 0.352 | 0.038 | 0.027 | 0.090 |
Dy | 2.722 | 7.779 | 7.546 | 0.067 | 2.102 | 0.015 | 0.116 | 0.105 | 0.034 | 0.037 | 0.061 | 0.009 | 2.374 | 0.287 | 0.106 | 0.650 |
Ho | 0.580 | 1.470 | 1.186 | 0.016 | 0.432 | 0.002 | 0.028 | 0.017 | 0.016 | 0.014 | 0.016 | - | 0.476 | 0.076 | 0.019 | 0.166 |
Er | 1.644 | 3.617 | 2.520 | 0.041 | 1.220 | 0.016 | 0.063 | 0.085 | - | 0.070 | 0.104 | - | 1.327 | 0.288 | 0.029 | 0.578 |
Tm | 0.237 | 0.522 | 0.318 | 0.012 | 0.168 | 0.003 | 0.019 | 0.016 | - | 0.014 | 0.030 | 0.002 | 0.188 | 0.047 | 0.007 | 0.103 |
Yb | 1.596 | 3.373 | 2.003 | 0.111 | 1.063 | - | 0.125 | 0.089 | 0.050 | 0.139 | 0.235 | 0.040 | 1.171 | 0.362 | 0.006 | 0.711 |
Lu | 1.778 | 7.392 | 5.266 | 0.011 | 0.155 | - | 0.015 | 0.021 | 0.009 | 0.026 | 0.055 | 0.002 | 0.158 | 0.057 | 0.003 | 0.158 |
Hf | 1.545 | 21.03 | 25.84 | 0.013 | 0.557 | 0.020 | 0.019 | 0.016 | 0.013 | 0.004 | 0.011 | 0.013 | 0.584 | 0.089 | 0.019 | 0.004 |
Ta | 0.027 | 0.790 | 1.166 | 0.004 | 0.004 | - | 0.012 | 0.008 | 0.018 | 0.003 | - | 0.002 | 0.007 | 0.001 | 0.006 | 0.022 |
Pb | 3.535 | 10.74 | 1.799 | 0.045 | 0.255 | 0.247 | 16.17 | 3.347 | 18.01 | 0.035 | 4.078 | - | 0.226 | 0.063 | 0.693 | 4.215 |
Th | 0.032 | 11.56 | 2.819 | 0.004 | 0.021 | 0.005 | 0.018 | 0.048 | 0.010 | - | 0.002 | - | 0.012 | 0.002 | 0.005 | 0.112 |
U | 0.015 | 1.653 | 0.412 | 0.002 | 0.011 | - | 0.035 | 0.083 | 0.043 | 0.001 | 0.003 | - | 0.005 | 0.003 | 0.011 | 0.216 |
Sample No. | Bulk-Rock Ores/Mineral Separates | Major Elements (wt.%, ICP-OES) | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
bulk-rock ores (Alkali dissolution) | SiO2 | TiO2 | Al2O3 | FeOT | MnO | MgO | CaO | Na2O | K2O | P2O5 | CuO | NiO | Cr2O3 | Total | |
Standard | BLANK | 0.019 | - | - | 0.001 | - | 0.001 | 0.027 | 0.002 | 0.001 | 0.007 | - | - | - | 0.058 |
BCR-2 | 55.44 | 2.265 | 13.12 | 12.21 | 0.196 | 3.603 | 7.092 | 3.175 | 1.841 | 0.385 | 0.002 | 0.002 | 0.003 | 99.34 | |
BHVO-2 | 50.43 | 2.728 | 13.10 | 10.84 | 0.166 | 7.205 | 11.27 | 2.167 | 0.499 | 0.284 | 0.014 | 0.017 | 0.040 | 98.76 | |
Whole ore | JC-1 | 24.89 | 0.062 | 0.626 | 24.49 | 0.126 | 25.20 | 0.411 | 0.039 | 0.061 | - | 2.682 | 2.500 | 0.501 | 81.59 |
JC-2 | 25.41 | 0.065 | 1.003 | 26.07 | 0.148 | 24.40 | 1.505 | 0.025 | 0.030 | - | 1.135 | 4.013 | 0.464 | 84.27 | |
JC-3 | 36.43 | 0.337 | 2.355 | 16.49 | 0.179 | 27.73 | 2.132 | 0.224 | 0.273 | 0.032 | 1.220 | 0.971 | 0.469 | 88.85 | |
JC-4 | 25.76 | 0.078 | 0.634 | 22.06 | 0.199 | 19.34 | 6.429 | 0.048 | 0.231 | 0.024 | 0.475 | 2.954 | 0.646 | 78.88 | |
Replicate samples | JC-3-R | 36.71 | 0.342 | 2.385 | 16.48 | 0.181 | 27.77 | 2.121 | 0.238 | 0.305 | 0.035 | 1.245 | 0.972 | 0.491 | 89.28 |
Silicate/oxide mineral separates (Acid dissolution) | SiO2 | TiO2 | Al2O3 | FeOT | MnO | MgO | CaO | Na2O | K2O | P2O5 | CuO | NiO | Cr2O3 | Total | |
JC-1 | Serpentine | - | 0.211 | 0.660 | 5.408 | 0.062 | 14.45 | 0.134 | 0.034 | 0.006 | 0.005 | 0.029 | 0.051 | 0.583 | 21.63 |
Magnetite | - | 0.911 | 8.449 | 64.00 | 0.564 | 2.704 | 0.094 | 0.006 | 0.013 | - | 0.063 | 0.127 | 23.92 | 100.9 | |
JC-2 | Serpentine | - | 0.050 | 2.310 | 9.460 | 0.095 | 27.39 | 0.144 | 0.007 | 0.002 | 0.007 | 0.027 | 0.073 | 0.373 | 39.94 |
Magnetite | - | 1.321 | 0.211 | 87.48 | 0.421 | 1.652 | 0.079 | 0.014 | 0.019 | 0.001 | 0.040 | 0.159 | 8.622 | 100.0 | |
JC-3 | Olivine | - | 0.035 | 0.145 | 16.15 | 0.226 | 38.57 | 0.328 | 0.008 | 0.002 | 0.013 | 0.002 | 0.183 | 0.080 | 55.74 |
Clinopyroxene | - | 0.537 | 3.789 | 6.274 | 0.167 | 19.37 | 19.51 | 0.346 | 0.027 | - | 0.004 | 0.029 | 0.968 | 51.02 | |
Orthopyroxene | - | 0.274 | 2.434 | 10.30 | 0.221 | 31.48 | 2.817 | 0.060 | 0.011 | 0.010 | 0.004 | 0.050 | 0.590 | 48.25 | |
JC-4 | Magnetite | - | 0.955 | 0.151 | 81.57 | 0.236 | 0.676 | 0.579 | 0.005 | - | - | 0.057 | 0.147 | 8.239 | 92.62 |
Replicate samples | JC-4 Magnetite-R | - | 0.955 | 0.148 | 82.03 | 0.236 | 0.679 | 0.536 | 0.004 | 0.001 | 0.002 | 0.062 | 0.158 | 9.016 | 93.83 |
Sulfide mineral separates (Acid dissolution) | Si | Ti | Al | Fe | Mn | Mg | Ca | Na | K | P | Cu | Ni | Cr | Total | |
JC-1 | Pyrrhotite (+Pentlandite) | - | 0.008 | 0.064 | 47.73 | 0.050 | 3.307 | 0.910 | 0.006 | 0.027 | 0.041 | 1.674 | 11.26 | 0.066 | 65.15 |
Chalcopyrite (+Pentlandite) | - | 0.008 | 0.029 | 37.87 | 0.012 | 0.586 | 0.373 | 0.001 | 0.041 | 0.332 | 18.73 | 15.52 | 0.004 | 73.50 | |
Pentlandite | - | 0.005 | 0.015 | 36.07 | 0.004 | 0.327 | 0.216 | 0.015 | 0.037 | 0.003 | 0.228 | 30.50 | 0.009 | 67.42 | |
JC-2 | Pyrrhotite (+Pentlandite) | - | 0.003 | 0.039 | 48.12 | 0.016 | 1.710 | 0.085 | - | 0.025 | 0.009 | 0.383 | 16.53 | 0.008 | 66.92 |
Chalcopyrite | - | 0.001 | 0.025 | 31.93 | 0.012 | 0.878 | 0.100 | - | 0.024 | 0.384 | 29.74 | 1.445 | 0.002 | 64.53 | |
Pentlandite | - | 0.003 | 0.007 | 34.02 | 0.004 | 0.483 | 0.041 | - | 0.018 | 0.008 | 0.680 | 34.92 | 0.002 | 70.18 | |
JC-3 | Pyrrhotite | - | 5.281 | 2.522 | 55.94 | 0.272 | 1.480 | 5.760 | 0.031 | 0.017 | - | 0.172 | 0.096 | 5.978 | 77.55 |
JC-4 | Pyrrhotite (+Pentlandite) | - | 0.002 | 0.012 | 59.24 | 0.002 | 0.225 | 0.091 | - | - | 0.003 | 0.526 | 6.114 | 0.010 | 66.22 |
Pentlandite | - | 0.004 | 0.012 | 33.40 | 0.002 | 0.260 | 0.323 | - | 0.017 | 0.017 | 0.761 | 35.16 | 0.003 | 69.96 | |
Replicate samples | JC-4 Pentlandite-R | - | 0.004 | 0.008 | 33.33 | 0.002 | 0.250 | 0.055 | - | 0.014 | 0.013 | 0.693 | 34.57 | 0.003 | 68.94 |
Sample No. | Mineral Separates | δ56Fe (‰) | 2SD | δ57Fe (‰) | 2SD |
---|---|---|---|---|---|
Standard | BCR-2 | 0.13 | 0.03 | 0.11 | 0.04 |
BHVO-2 | 0.11 | 0.02 | 0.03 | 0.05 | |
AGV-2 | 0.12 | 0.07 | 0.07 | 0.04 | |
W-2a | 0.02 | 0.02 | 0.03 | 0.07 | |
JC-1 | Pyrrhotite (+Pentlandite) | −0.82 | 0.04 | −1.19 | 0.09 |
Chalcopyrite (+Pentlandite) | 0.15 | 0.06 | 0.17 | 0.11 | |
Pentlandite | 0.53 | 0.03 | 0.86 | 0.04 | |
Serpentine | 0.60 | 0.05 | 0.88 | 0.05 | |
Magnetite | 0.24 | 0.04 | 0.38 | 0.03 | |
JC-2 | Pyrrhotite (+Pentlandite) | −0.16 | 0.01 | −0.26 | 0.05 |
Chalcopyrite | 0.50 | 0.04 | 0.65 | 0.06 | |
Pentlandite | 1.05 | 0.05 | 1.60 | 0.10 | |
Serpentine | 0.52 | 0.02 | 0.60 | 0.05 | |
Magnetite | 0.71 | 0.05 | 1.07 | 0.06 | |
JC-3 | Pyrrhotite | −0.77 | 0.05 | −1.17 | 0.07 |
Olivine | 0.07 | 0.03 | 0.11 | 0.09 | |
Clinopyroxene | 0.04 | 0.02 | −0.02 | 0.04 | |
Orthopyroxene | 0.05 | 0.07 | 0.03 | 0.09 | |
JC-4 | Pyrrhotite (+Pentlandite) | −0.90 | 0.03 | −1.33 | 0.05 |
Pentlandite | 1.02 | 0.04 | 1.57 | 0.04 | |
Magnetite | 0.50 | 0.03 | 0.79 | 0.06 | |
Replicate samples | JC-4 Pentlandite-R | 0.99 | 0.03 | 1.46 | 0.06 |
JC-4 Magnetite-R | 0.44 | 0.04 | 0.75 | 0.02 |
Part 1. Mineral Separates. | |||||||||
Sample No. | Mineral Separates | δ56Fe (Mineral Separate) | A2 = Sulfide Content of Mineral Separate (wt.%) | A3 = Fe Content of Mineral Separate | Value of Ci | ||||
(‰, from Table 5) | Pyrrhotite | Chalcopyrite | Pentlandite | (wt.%, from Table 4) | C(Pyrrhotite) | C(Chalcopyrite) | C(Pentlandite) | ||
JC-1 | Pyrrhotite (+Pentlandite) | −0.82 | 57.3 | 5.1 | 37.6 | 47.73 | 70.3 | 3.2 | 26.5 |
Chalcopyrite (+Pentlandite) | 0.15 | 5.4 | 49.4 | 45.2 | 37.87 | 9.6 | 44.5 | 45.8 | |
Pentlandite | 0.53 | - | - | ~100.0 | 36.07 | - | - | ~100.0 | |
JC-2 | Pyrrhotite (+Pentlandite) | −0.16 | 51.2 | - | 48.8 | 48.11 | 67.3 | - | 32.7 |
Chalcopyrite | 0.50 | 6.5 | 89.1 | 4.4 | 31.93 | 6.5 | 89.0 | 4.6 | |
Pentlandite | 1.05 | - | - | ~100.0 | 34.02 | - | - | ~100.0 | |
JC-3 | Pyrrhotite | −0.77 | ~100.0 | - | - | 56.79 | ~100.0 | - | - |
JC-4 | Pyrrhotite (+Pentlandite) | −0.90 | 82.6 | - | 17.4 | 59.23 | 90.2 | - | 9.8 |
Pentlandite | 1.02 | - | - | ~100.0 | 33.40 | - | - | ~100.0 | |
Part 2. Pure Sulfide End-Members after Calculation. | |||||||||
Sample No. | Sulfide Type | A1 = Fe Content of Each Sulfide | δ56Fei | ||||||
(wt.%, from Table 2) | ‰ | ||||||||
JC-1 | Pyrrhotite | 59.37 | −1.37 | ||||||
Chalcopyrite | 30.23 | 0.09 | |||||||
Pentlandite | 34.04 | 0.53 | |||||||
JC-2 | Pyrrhotite | 60.01 | −0.74 | ||||||
Chalcopyrite | 29.65 | 0.56 | |||||||
Pentlandite | 30.67 | 1.05 | |||||||
JC-3 | Pyrrhotite | 61.53 | −0.77 | ||||||
JC-4 | Pyrrhotite | 59.51 | −1.11 | ||||||
Pentlandite | 30.85 | 1.02 |
Sample no. | Ore-bearing Rock Type | Main Minerals Calculated in Order | Unique Element (mol.%) | The Remaining Elements and Their Contents (mol.%) |
---|---|---|---|---|
JC-1 | Sulfide-rich dunite | Chalcopyrite | Chalcopyrite = Cu | Fe = Fe − Cu, Cu = 0; |
Pentlandite | Pentlandite = Pn | Fe = Fe − Ni, Ni = 0; | ||
Chromite | chromite = Cr | Fe = Fe − Cr, Mg = Mg − Cr, Cr = 0; | ||
Serpentine | serpentine, olivine = Si, serpentine, olivine = Mg | Fe = Fe − Si (serpentine) − Si (olivine), Si = 0, Mg = 0; | ||
Olivine | ||||
Pyrrhotite | pyrrhotite = Fe | Fe = 0. | ||
JC-2 | sulfide-rich dunite | Chalcopyrite | Chalcopyrite = Cu | Fe = Fe − Cu, Cu = 0; |
Pentlandite | Pentlandite = Pn | Fe = Fe − Ni, Ni = 0; | ||
Serpentine | serpentine = Al | Si = Si − Al, Fe = Fe − Al, Cr = Cr − Al, Al = 0; | ||
Chromite | chromite = Cr | Fe = Fe − Cr, Cr = 0; | ||
Olivine | olivine = Si | Fe = Fe − Si, Si = 0; | ||
Pyrrhotite | pyrrhotite = Fe | Fe = 0. | ||
Only serpentine has a lot of Al in JC-2 (unlike chromite of JC-1, which also has a lot of Al) | ||||
JC-3 | sulfide-rich lherzolite | Chalcopyrite | Chalcopyrite = Cu | Fe = Fe − Cu, Cu = 0; |
Pentlandite | Pentlandite = Pn | Fe = Fe − Ni, Ni = 0; | ||
Chromite | chromite = Cr | Fe = Fe − Cr, Mg = Mg − Cr, Cr = 0; | ||
Plagioclase | plagioclase = Na | Ca = Ca − Na, Si = Si − Na, Al = Al − Na, Fe = Fe − Na, Na = 0; | ||
Clinopyroxene | clinopyroxene = Ca | Fe = Fe − Ca, Mg = Mg − Ca, Si = Si − Ca, Al = Al − Ca, Ca = 0; | ||
Orthopyroxene | orthopyroxene = Al | Fe = Fe − Al, Mg = Mg − Al, Si = Si − Al, Al = 0; | ||
Serpentine | serpentine, olivine = Si, serpentine, olivine = Mg | Fe = Fe − Si (serpentine) − Si (olivine), Si = 0, Mg = 0; | ||
Olivine | ||||
Pyrrhotite | pyrrhotite = Fe | Fe = 0. |
Sample No. | Mineral Type | Mineral Modal Abundance (wt.%, cal.) | Experimental Molecular Formula |
---|---|---|---|
JC-1 | Pyrrhotite | 13.43 | Fe0.855S |
Chalcopyrite | 6.734 | Cu0.944Fe0.959S2 | |
Pentlandite | 6.816 | (Fe4.531,Ni3.825)8.355S8 | |
Serpentine | 57.48 | (Mg5.145,Fe0.744,Mn0.060,Ti0.032,Cr0.117)6.099[(Si3.570,Al0.447)4.017O10](OH)8 | |
Olivine | 13.88 | (Mg1.720,Fe0.330)2.049Si0.975O4 | |
Chromite | 1.662 | (Mg0.165,Fe2+0.848,Mn0.012)1.024(Cr0.890,Al0.398,Fe3+0.664,Ti0.024)1.976O4 | |
JC-2 | Pyrrhotite | 14.24 | Fe0.852S |
Chalcopyrite | 2.945 | Cu0.912Fe0.930S2 | |
Pentlandite | 10.42 | (Fe4.125,Ni4.038)8.164S8 | |
Serpentine | 40.92 | (Mg5.353,Fe0.628,Cr0.033)6.014[(Si3.760,Al0.300)4.060O10](OH)8 | |
Olivine | 29.07 | (Mg1.654,Fe0.355)2.008Si0.996O4 | |
Chromite | 2.401 | (Mg0.037,Fe2+1.007)1.044(Cr0.409,Al0.01,Fe3+1.503,Ti0.044)1.956O4 | |
JC-3 | Pyrrhotite | 4.645 | Fe0.889S |
Chalcopyrite | 3.286 | Cu0.885Fe0.948S2 | |
Pentlandite | 2.788 | (Fe4.026,Ni3.507)7.533S8 | |
Serpentine | 8.062 | (Mg4.970,Fe2+0.982,Mn0.021,Ca0.040)6.014[(Si3.894,Fe3+0.132)4.026O10](OH)8 | |
Olivine | 41.14 | (Mg1.665,Fe0.358)2.024Si0.988O4 | |
Clinopyroxene | 8.996 | (Na0.021,Ca0.765,Mg1.040,Fe0.180,Cr0.032)2.039[(Si1.859,Al0.158)2.017O6] | |
Orthopyroxene | 24.65 | (Ca0.085,Mg1.643,Fe0.283,Cr0.018)2.028[(Si1.913,Al0.092)2.004O6] | |
Chromite | 1.362 | (Mg0.247,Fe2+0.782)1.029(Cr1.000,Al0.622,Fe3+0.320,Ti0.029)1.971O4 | |
Plagioclase | 5.073 | (Na0.423,K0.016,Ca0.559,Fe0.016)1.014Al1.568Si2.427O8 | |
JC-4 | Pyrrhotite | - | Fe0.826S |
Chalcopyrite | - | Cu0.897Fe0.937S2 | |
Pentlandite | - | (Fe3.997,Ni3.930)7.928S8 | |
Serpentine | - | (Mg4.688,Fe1.236,Ca0.018,Ni0.014)5.956[Si4.022O10](OH)8 |
Sample No. | Mineral Type | δ56Fei | B1 = Fe Content of Each Mineral | B2 = Sulfide Content of Bulk-Sulfide Phase | B3 = Fe Content of Bulk-Sulfide Phase | Value of Ci | δ56Fe (Sulfide Liquid) | |||
---|---|---|---|---|---|---|---|---|---|---|
‰, from Part 2 of Table 6 | wt.%, from Table 2 | wt.%, cal. from Table 8 | wt.% | wt.%, Corrected to 100% | Scenario (1), ‰ | Scenario (2), ‰ | Scenario (3), ‰ | Scenario (4), ‰ | ||
JC-1 | Pyrrhotite | −1.37 | 59.37 | 49.77 | 45.70 | 64.66 | −0.77 | −0.39 | −0.59 | 0.32 |
Chalcopyrite | 0.09 | 30.23 | 24.96 | 16.52 | ||||||
Pentlandite | 0.53 | 34.04 | 25.27 | 18.82 | ||||||
Serpentine | 0.60 | 6.998 | ||||||||
JC-2 | Pyrrhotite | −0.74 | 60.01 | 51.59 | 45.70 | 67.75 | −0.20 | −0.22 | −0.11 | 0.95 |
Chalcopyrite | 0.56 | 29.65 | 10.67 | 6.924 | ||||||
Pentlandite | 1.05 | 30.67 | 37.74 | 25.33 | ||||||
Serpentine | 0.52 | 6.015 |
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Wang, P.; Niu, Y.; Sun, P.; Wang, X.; Guo, P.; Gong, H.; Duan, M.; Shen, F.; Shi, Y.; Xue, S.; et al. 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, 11, 464. https://doi.org/10.3390/min11050464
Wang P, Niu Y, Sun P, Wang X, Guo P, Gong H, Duan M, Shen F, Shi Y, Xue S, et al. 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; 11(5):464. https://doi.org/10.3390/min11050464
Chicago/Turabian StyleWang, Peiyao, Yaoling Niu, Pu Sun, Xiaohong Wang, Pengyuan Guo, Hongmei Gong, Meng Duan, Fangyu Shen, Yining Shi, Song Xue, and et al. 2021. "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 11, no. 5: 464. https://doi.org/10.3390/min11050464