“…When Cu and Ca are above detection limits, Ca generally has a much higher concentration than Cu. The lack of overlap with VMS mineralisation is in keeping with a re-evaluation of the usefulness of this discrimination diagram by Bédard et al (2022) who showed in a study of magnetite compositions from 33 VMS deposits that 82% of the magnetite compositions fall outside of the VMS field. Fig.…”
Section: Discussionsupporting
confidence: 74%
“…Previous studies have been shown that the composition of magnetite can be used to fingerprint ore deposit types and provide insight into processes associated with the formation of VMS deposits (Singoyi et al , 2006; Kamvong et al , 2007; Dupuis and Beaudoin, 2011; Makvandi et al , 2013; 2016a, 2016b; Bédard et al , 2022). Using the composition of magnetite obtained from various VMS, skarn, iron oxide–Cu–Au, and Broken Hill-type Pb–Zn deposits, Singoyi et al (2006) and Kamvong et al (2007) suggested that these deposits can be distinguished on the basis of a plot of Sn/Ga vs .…”
Section: Magnetite In Metamorphosed Massive Sulfide Depositsmentioning
confidence: 99%
“…In addition to using scatter plots, multivariate statistical methods, including principal component analysis (PCA) and Random Forests, show promise in discriminating the trace-element signatures in different lithologies and ore deposit types (Bédard et al , 2022). Makvandi et al (2016b) showed, for example, that the trace-element composition of magnetite in massive sulfides, altered gahnite-rich dacite, gabbro and iron formation in the Izok Lake area could be distinguished using PCA.…”
Section: Magnetite In Metamorphosed Massive Sulfide Depositsmentioning
confidence: 99%
“…Magnetite-bearing ore deposits include Ni–Cu–PGE, banded iron formation (BIF), iron oxide–Cu–Au (IOCG), skarn, porphyry Cu, Fe–REE–Nb, Cu–Au–Fe, iron oxide–apatite, and volcanogenic massive sulfide (VMS) deposits (e.g. Pagé and Barnes, 2009; Dupuis and Beaudoin, 2011; Nadoll et al , 2012a; Dare et al , 2012; Makvandi et al , 2013; Acosta-Góngora et al , 2014; Huang et al , 2013, 2015; Chen et al , 2015; Chung et al , 2015; Pisiak et al , 2015; Xu et al , 2015; Zhao et al , 2015; Qi et al , 2021; Bédard et al , 2022).…”
Magnetite is a common mineral in the Paleoproterozoic Stollberg Zn–Pb–Ag plus magnetite ore field (~6.6 Mt of production), which occurs in 1.9 Ga metamorphosed felsic and mafic rocks. Mineralisation at Stollberg consists of magnetite bodies and massive to semi-massive sphalerite–galena and pyrrhotite (with subordinate pyrite, chalcopyrite, arsenopyrite and magnetite) hosted by metavolcanic rocks and skarn. Magnetite occurs in sulfides, skarn, amphibolite and altered metamorphosed rhyolitic ash–siltstone that consists of garnet–biotite, quartz–garnet–pyroxene, gedrite–albite, and sericitic rocks. Magnetite probably formed from hydrothermal ore-bearing fluids (~250–400°C) that replaced limestone and rhyolitic ash–siltstone, and subsequently recrystallised during metamorphism. The composition of magnetite from these rock types was measured using electron microprobe analysis and LA–ICP–MS. Utilisation of discrimination plots (Ca+Al+Mn vs. Ti+V, Ni/(Cr+Mn) vs. Ti+V, and trace-element variation diagrams (median concentration of Mg, Al, Ti, V, Co, Mn, Zn and Ga) suggest that the composition of magnetite in sulfides from the Stollberg ore field more closely resembles that from skarns found elsewhere rather than previously published compositions of magnetite in metamorphosed volcanogenic massive sulfide deposits. Although the variation diagrams show that magnetite compositions from various rock types have similar patterns, principal component analyses and element–element variation diagrams indicate that its composition from the same rock type in different sulfide deposits can be distinguished. This suggests that bulk-rock composition also has a strong influence on magnetite composition. Principal component analyses also show that magnetite in sulfides has a distinctive compositional signature which allows it to be a prospective pathfinder mineral for sulfide deposits in the Stollberg ore field.
“…When Cu and Ca are above detection limits, Ca generally has a much higher concentration than Cu. The lack of overlap with VMS mineralisation is in keeping with a re-evaluation of the usefulness of this discrimination diagram by Bédard et al (2022) who showed in a study of magnetite compositions from 33 VMS deposits that 82% of the magnetite compositions fall outside of the VMS field. Fig.…”
Section: Discussionsupporting
confidence: 74%
“…Previous studies have been shown that the composition of magnetite can be used to fingerprint ore deposit types and provide insight into processes associated with the formation of VMS deposits (Singoyi et al , 2006; Kamvong et al , 2007; Dupuis and Beaudoin, 2011; Makvandi et al , 2013; 2016a, 2016b; Bédard et al , 2022). Using the composition of magnetite obtained from various VMS, skarn, iron oxide–Cu–Au, and Broken Hill-type Pb–Zn deposits, Singoyi et al (2006) and Kamvong et al (2007) suggested that these deposits can be distinguished on the basis of a plot of Sn/Ga vs .…”
Section: Magnetite In Metamorphosed Massive Sulfide Depositsmentioning
confidence: 99%
“…In addition to using scatter plots, multivariate statistical methods, including principal component analysis (PCA) and Random Forests, show promise in discriminating the trace-element signatures in different lithologies and ore deposit types (Bédard et al , 2022). Makvandi et al (2016b) showed, for example, that the trace-element composition of magnetite in massive sulfides, altered gahnite-rich dacite, gabbro and iron formation in the Izok Lake area could be distinguished using PCA.…”
Section: Magnetite In Metamorphosed Massive Sulfide Depositsmentioning
confidence: 99%
“…Magnetite-bearing ore deposits include Ni–Cu–PGE, banded iron formation (BIF), iron oxide–Cu–Au (IOCG), skarn, porphyry Cu, Fe–REE–Nb, Cu–Au–Fe, iron oxide–apatite, and volcanogenic massive sulfide (VMS) deposits (e.g. Pagé and Barnes, 2009; Dupuis and Beaudoin, 2011; Nadoll et al , 2012a; Dare et al , 2012; Makvandi et al , 2013; Acosta-Góngora et al , 2014; Huang et al , 2013, 2015; Chen et al , 2015; Chung et al , 2015; Pisiak et al , 2015; Xu et al , 2015; Zhao et al , 2015; Qi et al , 2021; Bédard et al , 2022).…”
Magnetite is a common mineral in the Paleoproterozoic Stollberg Zn–Pb–Ag plus magnetite ore field (~6.6 Mt of production), which occurs in 1.9 Ga metamorphosed felsic and mafic rocks. Mineralisation at Stollberg consists of magnetite bodies and massive to semi-massive sphalerite–galena and pyrrhotite (with subordinate pyrite, chalcopyrite, arsenopyrite and magnetite) hosted by metavolcanic rocks and skarn. Magnetite occurs in sulfides, skarn, amphibolite and altered metamorphosed rhyolitic ash–siltstone that consists of garnet–biotite, quartz–garnet–pyroxene, gedrite–albite, and sericitic rocks. Magnetite probably formed from hydrothermal ore-bearing fluids (~250–400°C) that replaced limestone and rhyolitic ash–siltstone, and subsequently recrystallised during metamorphism. The composition of magnetite from these rock types was measured using electron microprobe analysis and LA–ICP–MS. Utilisation of discrimination plots (Ca+Al+Mn vs. Ti+V, Ni/(Cr+Mn) vs. Ti+V, and trace-element variation diagrams (median concentration of Mg, Al, Ti, V, Co, Mn, Zn and Ga) suggest that the composition of magnetite in sulfides from the Stollberg ore field more closely resembles that from skarns found elsewhere rather than previously published compositions of magnetite in metamorphosed volcanogenic massive sulfide deposits. Although the variation diagrams show that magnetite compositions from various rock types have similar patterns, principal component analyses and element–element variation diagrams indicate that its composition from the same rock type in different sulfide deposits can be distinguished. This suggests that bulk-rock composition also has a strong influence on magnetite composition. Principal component analyses also show that magnetite in sulfides has a distinctive compositional signature which allows it to be a prospective pathfinder mineral for sulfide deposits in the Stollberg ore field.
“…Hence the trace-element compositions of magnetite can be used to characterise a particular ore type (e.g. magnetite-bearing ore deposits including Ni–Cu–PGE, banded iron formation (BIF), iron oxide–Cu–Au (IOCG), skarn, porphyry Cu, Fe–REE–Nb, Cu–Au–Fe, iron oxide–apatite, and volcanogenic massive sulfide deposits (VMS)) as has been shown by Dupuis and Beaudoin (2011) and Bédard et al (2022). Of these deposit types, there is a general paucity of trace-element information for minerals from metamorphosed VMS deposits, with magnetite being the exception for which several studies have been undertaken (Singoyi et al , 2006; Kamvong et al , 2007; Dupuis and Beaudoin, 2011; Makvandi et al , 2013; 2016a, 2016b; Maghfouri et al , 2021; Bédard et al , 2022; Sun et al , 2022).…”
Orthoamphibole, clinoamphibole and magnetite are common minerals in altered rocks associated spatially with Palaeoproterozoic volcanogenic massive sulfide (VMS) deposits in Colorado, USA and metamorphosed to the amphibolite facies. These altered rocks are dominated by the assemblage orthoamphibole (anthophyllite/gedrite)–cordierite–magnetite±gahnite±sulfides. Magnetite also occurs in granitoids, banded iron formations, quartz garnetite, and in metallic mineralisation consisting of semi-massive pyrite, pyrrhotite, chalcopyrite, and sphalerite with subordinate galena, gahnite and magnetite; amphibole also occurs in amphibolite. The precursor to the anthophyllite/gedrite–cordierite assemblages was probably the assemblage quartz–chlorite formed from hydrothermal ore-bearing fluids (~250° to 400°C) associated with the formation of metallic minerals in the massive sulfide deposits.
Element–element variation diagrams for amphibole, magnetite and ilmenite based on LA-ICP-MS data and Principal Component Analysis (PCA) for orthoamphiboles and magnetite show a broad range of compositions which are primarily dependent upon the nature of the host rock associated spatially with the deposits. Although discrimination plots of Al/(Zn+Ca) vs Cu/(Si+Ca) and Sn/Ga vs Al/Co for magnetite do not indicate a VMS origin, the concentration of Al+Mn together with Ti+V and Sn vs Ti support a hydrothermal rather than a magmatic origin for magnetite. Principal Component Analyses also show that magnetite and orthoamphibole in metamorphosed altered rocks and sulfide zones have distinctive eigenvalues that allow them to be used as prospective pathfinders for VMS deposits in Colorado. This, in conjunction with the contents of Zn and Al in magnetite, Zn and Pb in amphibole, ilmenite and magnetite, the Cu content of orthoamphibole and ilmenite, and possibly the Ga and Sn concentrations of magnetite constitute effective exploration vectors.
The Avoca Tank orebody is one of a series of copper-rich orebodies occurring within the Girilambone Cu province of central New South Wales. Mineralisation at Avoca Tank is hosted within several narrow, chloritic, greenschist-facies shear zones which developed ~430 Ma (U-Pb titanite) within metasedimentary rocks around the margins of an Ordovician (ca. 470 Ma) mafic sill complex. Mineralisation at Avoca Tank preserves an early oxide phase (sulfide barren) as magnetite-rich shears that are overprinted by a pyrite-chalcopyrite-rich sulfide phase. The mineralogical and chemical footprint surrounding sulfide mineralisation is narrow (<50 m) offering limited ore vectoring using mineralogical and chemical change. However, magnetite-rich shears occur external to and within sulfide mineralised intervals, and magnetite within these shears displays distinctive trace element variation depending on proximity to Cu mineralisation. Changing magnetite trace element chemistry with increasing Cu abundance at Avoca Tank is best represented by two ternary systems. A ternary plot of Ni-V-Ti effectively separates magnetite from unmineralised zones via Ni abundance, while the ratio of Ti to V effectively separates magnetite from low-, moderate- and high-grade Cu zones. A ternary plot of Sn (100*Sn)-Zn-Ni effectively discriminates between unmineralised, low-grade and combined moderate- to high-grade zones. The greatest control here is the ratio of Zn to Sn, but the inclusion of Ni abundance provides a greater separation between low- versus combined high- and moderate-grade ore. Many of the trace element trends recorded in magnetite are mirrored in the overprinting sulfides. We propose a two-phase mineralising system, with initial development of chemically uniform, sulfide barren magnetite-chlorite-rich shear zones in proximity to the margins of older mafic sills. A subsequent, and potentially hotter (+60 °C), fluid harvested the early oxide for Fe, with the partial replacement, recrystallisation and re-equilibration magnetite within a sulfide-rich hydrothermal fluid under greenschist facies metamorphic conditions. As many known orebodies in the Girilambone Cu province are associated with magnetite-rich gangue, magnetic surveys are an effective exploration technique. Based on this pilot study, mapping trace element variation in magnetite within these bodies is an additional ore-vectoring technique in the search for economic Cu mineralisation in this province.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
