Geochemical and Isotopic Signature of Pyrite as a Proxy for Fluid Source and Evolution in the Candelaria-Punta del Cobre Iron Oxide Copper-Gold District, Chile

2020 ◽  
Vol 115 (7) ◽  
pp. 1493-1518
Author(s):  
I. del Real ◽  
J.F.H. Thompson ◽  
A. C. Simon ◽  
M. Reich
Keyword(s):  
Mass Spectrometry ◽  
Iron Oxide ◽  
Inductively Coupled Plasma ◽  
Hydrothermal Fluid ◽  
Sulfur Isotope ◽  
Isotopic Signature ◽  
Redox Conditions ◽  
Mass Spectrometry Data ◽  
Iocg Deposits ◽  
Copper Gold

Abstract Pyrite is ubiquitous in the world-class iron oxide copper-gold (IOCG) deposits of the Candelaria-Punta del Cobre district, documented from early to late stages of mineralization and observed in deep and shallow levels of mineralized bodies. Despite its abundance, the chemical and isotopic signature of pyrite from the Candelaria-Punta del Cobre district, and most IOCG deposits worldwide, remains poorly understood. We evaluated in situ chemical and isotopic variations at the grain scale in a set of pyrite-bearing samples collected throughout the district in order to characterize and further understand the nature of mineralization in this IOCG system. Our multianalytical approach integrated synchrotron micro-X-ray fluorescence (μ-XRF) mapping of pyrite grains with electron probe microanalysis and laser ablation-inductively coupled plasma-mass spectrometry data, and sulfur isotope determinations using secondary ion mass spectrometry (SIMS) complemented with bulk sulfur isotope analyses of coeval pyrite, chalcopyrite, and anhydrite. Synchrotron μ-XRF elemental concentration maps of individual pyrite grains reveal a strong zonation of Co, Ni, As, and Se. The observed relationships between Ni and Se are interpreted to reflect changes in temperature and redox conditions during ore formation and provide constraints on fluid evolution. Co and Ni concentrations and ratios suggest contributions from magmas of mafic-intermediate composition. Pyrite chemical concentrations reflect potential stratigraphic controls, where the sample from the upper part of the stratigraphy diverges from trends formed by the rest of the sample set from lower stratigraphic levels. The SIMS δ34S values of pyrite (and chalcopyrite) range between –2 up to 10‰, and bulk δ34S values of pyrite range between 4 up to 12‰. The majority of the δ34S analyses, falling between –1 and 2‰, indicate a magmatic source for sulfur and, by inference, for the hydrothermal ore fluid(s). Variation in the δ34S signature can be explained by changes in the redox conditions, fluid sources, and/or the temperature of the hydrothermal fluid. The Se/S ratio combined with δ34S values in pyrite is consistent with mixing between a magmatic-hydrothermal fluid and a fluid with a probable basinal signature. The results of this study are consistent with the hydrothermal fluids responsible for mineralization in the Candelaria-Punta del Cobre district being predominantly of magmatic origin, plausibly from mafic-intermediate magmas based on the Ni-Co content in pyrite. External fluid incursion, potentially from a basinal sedimentary source, occurred late in the evolution of the system, adding additional reduced sulfur as pyrite. There is no evidence to suggest that the late fluid added significant Cu-Au mineralization, but this cannot be ruled out. Finally, the data reveal that trace element ratios coupled with spatially resolved sulfur isotope data in pyrite are powerful proxies to track the magmatic-hydrothermal evolution of IOCG systems and help constrain the source of their contained metals.

scholarly journals On the origin of oldest Iron-Oxide-Copper-Gold (IOCG) deposits at the transition from Archean drip to plate tectonics

2020 ◽  
Author(s):  
Carlos E Ganade ◽  
William L. Griffin ◽  
Roberto F. Weinberg ◽  
Elena Belousova ◽  
Lynthener B. Takenaka ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Lithospheric Mantle ◽  
Plate Tectonics ◽  
Isotopic Signature ◽  
Trace Element Composition ◽  
Gold Deposits ◽  
Detrital Zircons ◽  
Geological Evidence ◽  
Iocg Deposits ◽  
Copper Gold

Abstract Geological evidence supports a significant change in Earth’s behaviour in the mid- to late Archaean, between 3.2 and 2.5 Ga, reflecting stabilization of the lithosphere and replacement of vertical tectonics by linear imbricated belts. At the heart of this change, the oldest (c. 2.75 Ga) Iron-Oxide-Copper-Gold deposits (IOCG) were formed in the Carajás Mineral Province (CMP) of the Amazon craton. U-Pb ages, Lu-Hf isotopes and trace element composition of detrital zircons from modern drainages record the crystallization ages of the exposed rocks of the CMP. Combined with the geochemistry of Archean granitoids in the CMP, we recognize four different age and compositional groups: 3.01-2.92 Ga TTG, 2.87-2.83 Ga transitional TTG + sanukitoid + K-rich granitoids, 2.78-2.72 Ga A-type crustal granites accompanying IOCGs, and 2.59-2.53 Ga alkaline high-K intrusions accompanied by renewed IOCG mineralization. The first two groups have a dominantly juvenile isotopic signature whereas the last two have evolved Hf-isotope signatures, accompanied by increase in K2O/Na2O, reflecting addition of old crustal components in the melting sources over time. The older juvenile granitoids are associated with dome-and-keel structures typical of granite-greenstone terranes, whereas the younger granitoids were emplaced along a linear shear belt associated with new mafic-ultramafic intrusions and remelting of older TTG. Based on the tectono-magmatic evolution, we argue that metasomatism and fertilization of the underlying lithospheric mantle by incompatible elements, necessary for the development of IOCG deposits, were related to vertical drip-tectonics during development of the TTG proto-continent. This proto-continent made the lithosphere rigid enough to allow linear translithospheric deformation to localize at c. 2.85 Ga, allowing decompression melting of the metasomatized lithospheric mantle in a restricted extensional setting to form abundant mafic and A-type granitoids at c. 2.75 Ga, and the first IOCG deposits on Earth.

scholarly journals Evidence of multiple halogen sources in scapolites from iron oxide-copper-gold (IOCG) deposits and regional Na Cl metasomatic alteration, Norrbotten County, Sweden

2017 ◽  
Vol 451 ◽  
pp. 90-103 ◽  
Author(s):  
Nelson F. Bernal ◽  
Sarah A. Gleeson ◽  
Martin P. Smith ◽  
Jaime D. Barnes ◽  
Yuanming Pan
Keyword(s):  
Iron Oxide ◽  
Metasomatic Alteration ◽  
Iocg Deposits ◽  
Copper Gold

MAPPING THE MINERAL ZONATION AT THE ERNEST HENRY IRON OXIDE COPPER-GOLD DEPOSIT: VECTORING TO Cu-Au MINERALIZATION USING MODAL MINERALOGY

2022 ◽  
Vol 117 (2) ◽  
pp. 485-494
Author(s):  
Tobias U. Schlegel ◽  
Renee Birchall ◽  
Tina D. Shelton ◽  
James R. Austin
Keyword(s):  
Iron Oxide ◽  
Gamma Ray ◽  
Geochemical Data ◽  
Iocg Deposits ◽  
Mineral Mapping ◽  
Gamma Ray Spectrometer ◽  
Mineral Assemblages ◽  
Copper Gold ◽  
Host Rocks ◽  
Acid Alteration

Abstract Iron oxide copper-gold (IOCG) deposits form in spatial and genetic relation to hydrothermal iron oxide-alkali-calcic-hydrolytic alteration and thus show a mappable zonation of mineral assemblages toward the orebody. The mineral zonation of a breccia matrix-hosted orebody is efficiently mapped by regularly spaced samples analyzed by the scanning electron microscopy-integrated mineral analyzer technique. The method results in quantitative estimates of the mineralogy and allows the reliable recognition of characteristic alteration as well as mineralization-related mineral assemblages from detailed mineral maps. The Ernest Henry deposit is located in the Cloncurry district of Queensland and is one of Australia’s significant IOCG deposits. It is known for its association of K-feldspar altered clasts with iron oxides and chalcopyrite in the breccia matrix. Our mineral mapping approach shows that the hydrothermal alteration resulted in a characteristic zonation of minerals radiating outward from the pipe-shaped orebody. The mineral zonation is the result of a sequence of sodic alteration followed by potassic alteration, brecciation, and, finally, by hydrolytic (acid) alteration. The hydrolytic alteration primarily affected the breccia matrix and was related to economic mineralization. Alteration halos of individual minerals such as pyrite and apatite extend dozens to hundreds of meters beyond the limits of the orebody into the host rocks. Likewise, the Fe-Mg ratio in hydrothermal chlorites changes systematically with respect to their distance from the orebody. Geochemical data obtained from portable X-ray fluorescence (p-XRF) and petrophysical data acquired from a magnetic susceptibility meter and a gamma-ray spectrometer support the mineralogical data and help to accurately identify mineral halos in rocks surrounding the ore zone. Specifically, the combination of mineralogical data with multielement data such as P, Mn, As, P, and U obtained from p-XRF and positive U anomalies from radiometric measurements has potential to direct an exploration program toward higher Cu-Au grades.

Compound Specific Stable Sulfur Isotope Analysis (δ34S and δ33S) of Organic Compounds Using Gas Chromatography Hyphenated with Multiple Collector Inductively Coupled Plasma Mass Spectrometry (GC-MC-ICPMS)

2020 ◽  
Author(s):  
Kümmel Steffen ◽  
Gelman Faina ◽  
Horst Axel ◽  
Strauß Harald ◽  
Gehre Matthias
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Organic Compounds ◽  
Inductively Coupled Plasma ◽  
Sulfur Isotope ◽  
Sulfur Isotopes ◽  
Isotope Analysis ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry ◽  
Stable Sulfur Isotope

<p>Stable sulfur isotope analysis is potentially applicable in various fields in forensics and environmental analytics to investigate the sources and degradation of organic compounds, many of them being priority pollutants in groundwater and the atmosphere. A broader use of sulfur isotopes of organic compounds in environmental studies is still hampered by the availability of precise and easy-to-use techniques. Here we present a method for the determination of stable sulfur isotope ratios using gas chromatography coupled with multiple-collector inductively coupled plasma mass spectrometry (GC-MC-ICPMS) which can be used for both δ<sup>34</sup>S and δ<sup>33</sup>S analysis. The method was evaluated using the reference materials IAEA-S-1, IAEA-S-2 and IAEA-S-3 which were converted offline to SF<sub>6</sub> prior to analysis. Standardization was carried out by using a two-point calibration approach. The δ<sup>34</sup>S values obtained by our method are in good agreement (within analytical uncertainty) with the results obtained by the conventional dual inlet method. Additionally, the impact of the used mass resolution (low and medium), the influence of auto-protonation of sulfur isotopes and the effect of isobaric interferences of O<sub>2</sub><sup>+</sup> on the obtained isotopic ratios was investigated. The analytical precision (1σ) for δ<sup>34</sup>S and δ<sup>33</sup>S values was usually better than ±0.1 ‰ for analytes containing >0.1 nmol S. Thus, the presented compound-specific online method should be sufficiently precise to address a wide variety of research questions involving mass independent isotope effects of sulfur-containing organic compounds to discriminate sources or biological and chemical reactions in the environment.</p>

scholarly journals LaserTRAM-DB: A Time Resolved Analysis Module for the complete reduction of Laser Ablation Inductively Coupled Plasma Mass Spectrometry data

2021 ◽  
Author(s):  
Jordan Lubbers ◽  
Adam Kent ◽  
Chris Russo
Keyword(s):  
Mass Spectrometry ◽  
Laser Ablation ◽  
Inductively Coupled Plasma ◽  
User Interaction ◽  
Analysis Data ◽  
Mass Spectrometry Data ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Plasma Mass Spectrometry ◽  
Geologic Samples

LaserTRAM-DB is a dashboard for the complete processing pipeline of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) data in complex materials such as geologic samples. As LA-ICP- MS data in geologic samples frequently have multiple phases, inclusions, and other compositional complexities within them that do not represent the material of interest, user interaction is required to filter unwanted signals out of the overall ablation signal. LaserTRAM-DB allows the user to filter which portion of the ablation peak is utilized in calculating concentrations, subsequently allowing for more accurate data to be obtained. Furthermore, it allows for the processing of both individual spot analysis data and a line of spots gathered in rapid succession, reducing the time required for data reduction while preserving spatial definition and still ensuring data quality.

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