scholarly journals Iron Isotope Fractionation during Skarn Cu-Fe Mineralization

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 444
Author(s):  
Song Xue ◽  
Yaoling Niu ◽  
Yanhong Chen ◽  
Yining Shi ◽  
Boyang Xia ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Isotope Fractionation ◽  
Inverse Correlation ◽  
Ore Deposits ◽  
Equilibrium Line ◽  
Skarn Deposit ◽  
Fe Isotopes ◽  
Pyrite Formation ◽  
Skarn Deposits ◽  
Pathway Effect

Fe isotopes have been applied to the petrogenesis of ore deposits. However, the behavior of iron isotopes in the mineralization of porphyry-skarn deposits is still poorly understood. In this study, we report the Fe isotopes of ore mineral separations (magnetite, pyrite, chalcopyrite and pyrrhotite) from two different skarn deposits, i.e., the Tonglvshan Cu-Fe skarn deposit developed in an oxidized hydrothermal system and the Anqing Cu skarn deposit developed in a reduced hydrothermal system. In both deposits, the Fe isotopes of calculated equilibrium fluids are lighter than those of the intrusions responsible for the skarn and porphyry mineralization, corroborating the “light-Fe fluid” hypothesis. Interestingly, chalcopyrite in the oxidized-Tonglvshan skarn deposit has lighter Fe than chalcopyrite in the reduced-Anqing skarn deposit, which is best understood as the result of the prior precipitation of magnetite (heavy Fe) from the ore fluid in the oxidized-Tonglvshan systems and the prior precipitation of pyrrhotite (light Fe) from the ore fluid in the reduced-Anqing system. The δ56Fe for pyrite shows an inverse correlation with δ56Fe of magnetite in the Tonglvshan. In both deposits, the Fe isotope fractionation between chalcopyrite and pyrite is offset from the equilibrium line at 350 °C and lies between the FeS-chalcopyrite equilibrium line and pyrite-chalcopyrite equilibrium line at 350 °C. These observations are consistent with the FeS pathway towards pyrite formation. That is, Fe isotopes fractionation during pyrite formation depends on a path from the initial FeS-fluid equilibrium towards the pyrite-fluid equilibrium due to the increasing extent of Fe isotopic exchange with fluids. This finding, together with the data from other deposits, allows us to propose that the pathway effect of pyrite formation in the Porphyry-skarn deposit mineralization is the dominant mechanism that controls Fe isotope characteristics.

scholarly journals Iron Isotopes Constrain the Metal Sources of Skarn Deposits: A Case Study from the Han-Xing Fe Deposit, China

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 951
Author(s):  
Bin Zhu ◽  
Hongfu Zhang ◽  
M. Santosh ◽  
Benxun Su ◽  
Pengfei Zhang ◽  
...  
Keyword(s):  
Major Elements ◽  
Ore Deposits ◽  
Magmatic Fluid ◽  
Skarn Deposit ◽  
Mass Balance Calculation ◽  
Positive Correlation ◽  
Fe Isotopes ◽  
Magmatic Fluids ◽  
Skarn Deposits

Magmatic fluids and leaching of rocks are regarded as the two sources of magmatic hydrothermal deposits, but their relative contributions to the metals in the deposits are still unclear. In this study, we combine major elements and Fe isotopes in two sets of rocks from the Han-Xing iron skarn deposit in China to constrain the iron sources. The positive correlation between the δ56Fe and ∑Fe2O3/TiO2 of altered diorites (∑Fe2O3 refers to the total iron) demonstrates that heavy Fe isotopes are preferentially leached from diorites during hydrothermal alteration. However, except for the pyrite, all the rocks and minerals formed in the skarn deposit are enriched in the light Fe isotope relative to the fresh/less altered diorites. Therefore, besides the leaching of rocks, the Fe isotopically light magmatic fluid also provides a large quantity of iron for this deposit. Based on the mass balance calculation, we conclude that iron from magmatic fluid is almost 2.6 times as large as that from the leaching of rocks. This is the first study to estimate the relative proportions of iron sources for Fe deposits by using Fe isotopes. Here, we propose that the high δ56Fe of magmatic intrusions combining the positive correlation between their ∑Fe2O3/TiO2 and δ56Fe could be taken as a fingerprint of exsolution or interaction with magmatic fluids, which contributes to the exploration of magmatic hydrothermal ore deposits.

scholarly journals The Role of Magmatic and Hydrothermal Fluids in the Formation of the Sasa Pb-Zn-Ag Skarn Deposit, Republic of Macedonia

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 444
Author(s):  
Sabina Palinkaš ◽  
Zlatko Peltekovski ◽  
Goran Tasev ◽  
Todor Serafimovski ◽  
Danijela Šmajgl ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Water Activity ◽  
Base Metal ◽  
Ore Deposits ◽  
Molar Ratio ◽  
Low Oxygen ◽  
Skarn Deposit ◽  
Ground Waters ◽  
Mineral Assemblages ◽  
Skarn Deposits

The Sasa Pb-Zn-Ag deposit belongs to the group of distal base metal skarn deposits. The deposit is located within the Serbo-Macedonian massif, a metamorphosed crystalline terrain of Precambrian to Paleozoic age. The mineralization, hosted by Paleozoic marbles, shows a strong lithological control. It is spatially and temporally associated with the calc-alkaline to shoshonitic post-collisional magmatism that affected the Balkan Peninsula during the Oligocene–Miocene time period and resulted in the formation of numerous magmatic–hydrothermal ore deposits. The mineralization at the Sasa Pb-Zn-Ag deposit shows many distinctive features typical for base metal skarn deposits including: (1) a carbonate lithology as the main immediate host of the mineralization; (2) a close spatial relation between the mineralization and magmatic bodies of an intermediate composition; (3) a presence of the prograde anhydrous Ca-Fe-Mg-Mn-silicate and the retrograde hydrous Ca-Fe-Mg-Mn ± Al-silicate mineral assemblages; (4) a deposition of base metal sulfides, predominately galena and sphalerite, during the hydrothermal stage; and (5) a post-ore stage characterized by the deposition of a large quantity of carbonates. The relatively simple, pyroxene-dominated, prograde mineralization at the Sasa Pb-Zn-Ag skarn deposit represents a product of the infiltration-driven metasomatism which resulted from an interaction of magmatic fluids with the host marble. The prograde stage occurred under conditions of a low water activity, low oxygen, sulfur and CO2 fugacities and a high K+/H+ molar ratio. The minimum pressure–temperature (P–T) conditions were estimated at 30 MPa and 405 °C. Mineralizing fluids were moderately saline and low density Ca-Na-chloride bearing aqueous solutions. The transition from the prograde to the retrograde stage was triggered by cooling of the system below 400 °C and the resulting ductile-to-brittle transition. The brittle conditions promoted reactivation of old (pre-Tertiary) faults and allowed progressive infiltration of ground waters and therefore increased the water activity and oxygen fugacity. At the same time, the lithostatic to hydrostatic transition decreased the pressure and enabled a more efficient degassing of magmatic volatiles. The progressive contribution of magmatic CO2 has been recognized from the retrograde mineral paragenesis as well as from the isotopic composition of associated carbonates. The retrograde mineral assemblages, represented by amphiboles, epidote, chlorites, magnetite, pyrrhotite, quartz and carbonates, reflect conditions of high water activity, high oxygen and CO2 fugacities, a gradual increase in the sulfur fugacity and a low K+/H+ molar ratio. Infiltration fluids carried MgCl2 and had a slightly higher salinity compared to the prograde fluids. The maximum formation conditions for the retrograde stage are set at 375 °C and 200 MPa. The deposition of ore minerals, predominantly galena and sphalerite, occurred during the hydrothermal phase under a diminishing influence of magmatic CO2. The mixing of ore-bearing, Mg-Na-chloride or Fe2+-chloride, aqueous solutions with cold and diluted ground waters is the most plausible reason for the destabilization of metal–chloride complexes. However, neutralization of relatively acidic ore-bearing fluids during the interaction with the host lithology could have significantly contributed to the deposition. The post-ore, carbonate-dominated mineralization was deposited from diluted Ca-Na-Cl-bearing fluids of a near-neutral pH composition. The corresponding depositional temperature is estimated at below 300 °C.

U-Pb dating of skarn garnets from Bulgarian deposits

2020 ◽  
Author(s):  
Rossitsa Vassileva ◽  
Valentin Grozdev ◽  
Irena Peytcheva ◽  
Albrecht von Quadt ◽  
Maria Stifeeva
Keyword(s):  
Age Determination ◽  
Major Elements ◽  
Ore Deposits ◽  
Skarn Deposit ◽  
Garnet Composition ◽  
Icp Ms ◽  
Tectonic Zones ◽  
Skarn Deposits ◽  
Hydrothermal Ore Deposits

<p>Calcic garnets from grossular-andradite (grandite) series have proven their ability to record the conditions and timing of their formation processes. Typically these minerals occur in skarn systems, together with other calc-silicates (diopside, epidote) and commonly host economic Cu, Zn-Pb-Ag, Au, Sn, W or Mo mineralization. Based on the U-content in the garnet structure, we used in-situ LA-ICP-MS U-Pb geochronology to determine the age record in more than 15 skarn deposits from different tectonic zones in Bulgaria. The data is partly complemented with ID-TIMS dating. The mineralogical, geochemical and petrological characteristics of the materials were described additionally. Both contact and infiltration skarns were studied.</p><p>The obtained data revealed that the garnet composition in terms of major elements does not affect the precision of age determination. Both andradite and grossular members yield age data with very high accuracy. The dating results, however, depend on the geochemical signature of the garnets and especially on the U-content and U/Pb ratio. Our data shows that skarn samples from the vicinities of magmatic bodies or along contacts of causative pegmatite veins usually have increased U-incorporation from several to more than 70 ppm, as suggested by their proximal position to the source. The contact skarn garnets formed by intrusion of silicate melts (or pegmatites) onto carbonate-rich hosts mostly produce precise ages, which are in good agreement with the geochronological zircon data about the magmatism in the studied regions (e.g. Central Pirin, Teshevo, Plana, Gutsal, Rila-West Rhodope, Sv. Nikola etc. plutons). The infiltration skarns, though, generally reveal ages with low accuracy and significant errors, mainly due to U-content below 1 ppm. The reason for the low U-concentration and U/Pb ratio is either connected with a primary U-deficit and its depletion in the garnet-precipitating fluids with time and space but might be also related to garnet retrograde hydrothermal alteration.</p><p>The time span of the Bulgarian skarn garnets is closely connected with the causative magmatic bodies. The studied skarns reveal Paleogene (~30-42 Ma - Central Pirin and Teshevo plutons and pegmatites from Rila-West Rhodope batholith; Djurkovo, Murzian and Zvezdel Pb-Zn deposits; ~ 58 Ma - skarns from Western Rila Mts., ~ 68 Ma – Babyak Mo-Ag-Au-W-Bi-Cu-Pb-Zn deposit), Cretaceous (~ 76 Ma- Gutsal pluton, 81 Ma - scheelite bearing skarns from the Plana pluton, 86 Ma – Iglika skarn deposit) and Paleozoic (~ 303 Ma – Martinovo Fe-skarn deposit) ages. Given the occurrence of Ca-garnet in contact rocks and hydrothermal ore deposits, our results highlight the potential of grandite as a powerful U-Pb geochronometer for dating magmatism and skarn-related mineralizations.</p><p><em>Acknowledgements.</em> The study is partly supported by the DNTS 02/15 bilateral project between Bulgaria and the Russian Federation, financed by the Bulgarian National Science Fund.</p>

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...

scholarly journals More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Elaheh Lotfi-Kalahroodi ◽  
Anne-Catherine Pierson-Wickmann ◽  
Olivier Rouxel ◽  
Rémi Marsac ◽  
Martine Bouhnik-Le Coz ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Isotope Fractionation ◽  
Isotopic Fractionation ◽  
Isotopic Signature ◽  
Organic Ligands ◽  
Riparian Wetland ◽  
Fe Isotopes ◽  
Preferential Binding ◽  
Isotope Systematics

AbstractAlthough redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes progressively dominate the solution composition in response to their binding with large biologically-derived organic ligands. Confronted with field data, these results demonstrate that Fe isotope systematics in wetlands are controlled by the OM flux, masking Fe isotope fractionation arising from redox reactions. This work sheds light on an overseen aspect of Fe isotopic fractionation and calls for a reevaluation of the parameters controlling the Fe isotopes fractionation to clarify the interpretation of the Fe isotopic signature.

scholarly journals Silicon Isotope Geochemistry: Fractionation Linked to Silicon Complexations and Its Geological Applications

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1415 ◽  
Author(s):  
Wang ◽  
Wei ◽  
Jiang ◽  
Liu ◽  
Lei ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
Isotope Fractionation ◽  
Isotope Geochemistry ◽  
Ore Deposits ◽  
Silicon Isotope ◽  
Core Formation ◽  
Silicon Isotopes ◽  
Silica Precipitation ◽  
Geological Processes ◽  
Biological Uptake

The fundamental advances in silicon isotope geochemistry have been systematically demonstrated in this work. Firstly, the continuous modifications in analytical approaches and the silicon isotope variations in major reservoirs and geological processes have been briefly introduced. Secondly, the silicon isotope fractionation linked to silicon complexation/coordination and thermodynamic conditions have been extensively stressed, including silicate minerals with variable structures and chemical compositions, silica precipitation and diagenesis, chemical weathering of crustal surface silicate rocks, biological uptake, global oceanic Si cycle, etc. Finally, the relevant geological implications for meteorites and planetary core formation, ore deposits formation, hydrothermal fluids activities, and silicon cycling in hydrosphere have been summarized. Compared to the thermodynamic isotope fractionation of silicon associated with high-temperature processes, that in low-temperature geological processes is much more significant (e.g., chemical weathering, biogenic/non-biogenic precipitation, biological uptake, adsorption, etc.). The equilibrium silicon isotope fractionation during the mantle-core differentiation resulted in the observed heavy isotope composition of the bulk silicate Earth (BSE). The equilibrium fractionation of silicon isotopes among silicate minerals are sensitive to the Si–O bond length, Si coordination numbers (CN), the polymerization degrees of silicate unites, and the electronegativity of cations in minerals. The preferential enrichment of different speciation of dissoluble Si (DSi) (e.g., silicic acid H4SiO40 (H4) and H3SiO4− (H3)) in silica precipitation and diagenesis, and chemical weathering, lead to predominately positive Si isotope signatures in continental surface waters, in which the dynamic fractionation of silicon isotope could be well described by the Rayleigh fractionation model. The role of complexation in biological fractionations of silicon isotopes is more complicated, likely involving several enzymatic processes and active transport proteins. The integrated understanding greatly strengthens the potential of δ30Si proxy for reconstructing the paleo terrestrial and oceanic environments, and exploring the meteorites and planetary core formation, as well as constraining ore deposits and hydrothermal fluid activity.

scholarly journals Comment on "Abiotic Pyrite Formation Produces a Large Fe Isotope Fractionation"

Science ◽  
2012 ◽  
Vol 335 (6068) ◽  
pp. 538-538 ◽  
Author(s):  
A. D. Czaja ◽  
C. M. Johnson ◽  
K. E. Yamaguchi ◽  
B. L. Beard
Keyword(s):  
Isotope Fractionation ◽  
Pyrite Formation

Lead and Silver Production in the Montevecchio Basin (Western Sardinia, Italy)

1996 ◽  
Vol 462 ◽  
Author(s):  
G.M. Ingo ◽  
T. Agus ◽  
R. Ruggeri ◽  
A. Amore Bonapasta ◽  
G. Bultrini ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Lead Isotope ◽  
Isotope Analysis ◽  
Ore Deposits ◽  
Smelting Process ◽  
Metal Production ◽  
Lead Isotope Analysis ◽  
Rule Out ◽  
Good Agreement

ABSTRACTLead slags and lead pieces, chronologically related to the Punic and Roman periods (IV BC - II AC), have been found at Bocche di Sciria, in the basin of the Montevecchio mine (south-western Sardinia, Italy). Furthermore, along the coast of this area over than 20 Punic and Roman shipwrecks with charges of lead ingots have been found. These materials indicate intense pyrometallurgical activities and the presence of metal production centres very close to the metal ore deposits. The microchemical studies of the slags have shown that they can be associated to a smelting process for lead and silver production. Furthermore, lead isotope analysis has been carried out for lead ores from Montevecchio and for the lead slags, litharge, lead pieces found there. The results for lead ores are in good agreement with literature and the scatter of data for slags, litharge and lead pieces suggest to rule out a lead isotope fractionation in ancient lead and silver production.

Fluid speciation controls of low temperature copper isotope fractionation applied to the Kupferschiefer and Timna ore deposits

2009 ◽  
Vol 262 (3-4) ◽  
pp. 147-158 ◽  
Author(s):  
Dan Asael ◽  
Alan Matthews ◽  
Slawomir Oszczepalski ◽  
Miryam Bar-Matthews ◽  
Ludwik Halicz
Keyword(s):  
Low Temperature ◽  
Isotope Fractionation ◽  
Ore Deposits ◽  
Copper Isotope

scholarly journals Response to Comment on "Abiotic Pyrite Formation Produces a Large Fe Isotope Fractionation"

Science ◽  
2012 ◽  
Vol 335 (6068) ◽  
pp. 538-538 ◽  
Author(s):  
R. Guilbaud ◽  
I. B. Butler ◽  
R. M. Ellam
Keyword(s):  
Isotope Fractionation ◽  
Pyrite Formation
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