Discriminant diagrams for iron oxide trace element fingerprinting of mineral deposit types

Mineralium Deposita (Impact Factor: 2.56). 04/2011; 46(4):319-335. DOI: 10.1007/s00126-011-0334-y


Magnetite and hematite are common minerals in a range of mineral deposit types. These minerals form partial to complete solid
solutions with magnetite, chromite, and spinel series, and ulvospinel as a result of divalent, trivalent, and tetravalent
cation substitutions. Electron microprobe analyses of minor and trace elements in magnetite and hematite from a range of mineral
deposit types (iron oxide-copper-gold (IOCG), Kiruna apatite–magnetite, banded iron formation (BIF), porphyry Cu, Fe-Cu skarn,
Fe-Ti, V, Cr, Ni-Cu-PGE, Cu-Zn-Pb volcanogenic massive sulfide (VMS) and Archean Au-Cu porphyry and Opemiska Cu veins) show
compositional differences that can be related to deposit types, and are used to construct discriminant diagrams that separate
different styles of mineralization. The Ni + Cr vs. Si + Mg diagram can be used to isolate Ni-Cu-PGE, and Cr deposits from
other deposit types. Similarly, the Al/(Zn + Ca) vs. Cu/(Si + Ca) diagram can be used to separate Cu-Zn-Pb VMS deposits from
other deposit types. Samples plotting outside the Ni-Cu-PGE and Cu-Zn-Pb VMS fields are discriminated using the Ni/(Cr + Mn)
vs. Ti + V or Ca + Al + Mn vs. Ti + V diagrams that discriminate for IOCG, Kiruna, porphyry Cu, BIF, skarn, Fe-Ti, and V deposits.

KeywordsMagnetite–Hematite–Mineral deposit–Electron microprobe–Mineral chemistry–Discriminant diagram

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Available from: Georges Beaudoin
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    • "Magnetite composition from a wide variety of iron deposit types has been the focus of many recent studies (e.g., Dupuis and Beaudoin, 2011; Huang et al., 2013; McQueen and Cross, 1998). Those studies have demonstrated that trace elemental compositions of iron oxides are important for the understanding of the origin of different mineralization styles (Müller et al., 2003; Carew, 2004; Singoyi et al., 2006; Anderson et al., 2008; Dupuis and Beaudoin, 2011; Dare et al., 2012; Nadoll et al., 2014; Chen et al., 2015; Huang et al., 2015; Liu et al., 2015; Zhao Ore Geology Reviews 65 (2015) 917–928 ⁎ Corresponding author. "
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    ABSTRACT: Keywords: Magnetite Trace elements LA–ICP-MS Late Palaeoproterozoic Iron formation Labrador Trough Sokoman Formation Canada The Sokoman Iron Formation in the Labrador Trough, Canada, a typical granular iron formation (GIF), is coeval with the ~1.88 Ga Nimish volcanic suites in the same region. It is composed of the Lower, Middle and Upper Iron Formations. In addition to primary and altered magnetite in iron formations of the Hayot Lake, Rainy Lake and Wishart Lake areas, magnetite in volcanic breccia associated with the iron formation is identified for the first time in the stratigraphy. Trace elemental compositions of the most primary, altered and volcanic brecciated magnetite of the Sokoman Iron Formation were obtained by LA–ICP-MS. Commonly detected trace elements of magnetite include Ti, Al, Mg, Mn, V, Cr, Co and Zn. These three types of magnetite have different trace elemental compositions. Primary magnetite in the iron formation has a relatively narrow range of compositions with the depletion of Ti, Pb, Mg and Al. Magnetite from volcanic breccia is rich in Ti, Al, V, Mn, Mg, Zn, Cu and Pb, indicative of crystallization from mantle-derived magmas. Altered magnetite in the iron formation shows a relatively wide range of trace elemental compositions. Mineralizing fluids associated with magmas that generated the ~1.88 Ga Nimish volcanic suites circulated through the sedimentary piles to further enrich the iron formations and to form magnetite with variable compositions. The comparisons of different types of primary and altered magnetite in the iron formation in the region show distinct provenance discrimination. Our findings also support the origin of iron formations in association with multiple stages of exhalative volcanic and hydrothermal processes.
    Full-text · Article · Nov 2015 · Ore Geology Reviews
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    • "These concentrations and distributions are useful for discriminating types of mineralization, tracing the provenance of detrital/alluvial oxide resources and understanding the genesis of an ore deposit (e.g. Dupuis and Beaudoin 2011; Nadoll et al. 2014; Boutroy et al. 2014). Moreover, the recent discovery of U and Pb in hematite shows the potential application of Fe-oxides as geochronometers to provide direct ages and estimate the lifespan for mineralization (Ciobanu et al. 2013). "
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    ABSTRACT: Iron oxides, the dominant minerals in the giant Olympic Dam IOCG deposit, contain concentrations of more than 25 trace elements at concentrations measurable by LA-ICP-MS, including several elements not commonly reported (or analyzed for). Mineral geochemical signatures based on W, U, Sn and Mo (named 'granito-phile' elements), and chondrite-normalized REY fractionation trends for hematite and magnetite show promise to distinguish discrete generations of Fe-oxides when interpreted in their petrographic context. Fe-oxides are possibly the main mineral repositories of elements such as W, Mo and Sn, and may play significant roles in the overall mineralogical balance of several others, notably U and REY.
    Full-text · Conference Paper · Aug 2015
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    • "Under high current conditions a wide beam diameter is needed to prevent heating of magnetite. Analytical conditions were similar to that of Dupuis and Beaudoin (2011) and Boutroy et al. (2014). Simple oxides (GEO Standard Block of P and H Developments) and/or natural minerals (Mineral Standard Mount MINM 25–53, Astimex Scientific; Jarosewich et al., 1980) were used to calibrate the instrument. "
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    ABSTRACT: Magnetite grains from the Izok Lake (Nunavut, Canada) and the Halfmile Lake (New Brunswick, Canada) volcanogenic massive sulfide deposits, and from till covering the nearby areas were investigated using the scanning electron microscopy (SEM), electron probe micro-analyzer (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and optical microscopy. The method of robust estimation for compositional data (rob-composition) was applied to censored geochemical data, and the results were analyzed by principal component analysis (PCA). Textural relationships and mineral association of magnetite reveal the history of formation, and contribute to the explanation of characteristic compositional differences of magnetite from different geological settings. The integration of petrography and mineral chemistry allows discriminating magmatic, metamorphic and hydrothermal magnetite grains in the VMS deposits bedrock samples. Magmatic magnetite is found in Izok Lake gabbro, and Halfmile Lake syenite, felsic ash tuff and gossan samples, whereas magnetite in Izok Lake massive sulfides, gahnite-rich dacite and iron formations formed during the amphibolite facies metamorphism. In Halfmile Lake andesite, magnetite recrystallized during greenschist facies metamorphism. In the magnetite alteration zone associated to the Halfmile Lake deposit, hydrothermal magnetite has been overprinted by metamorphic magnetite. Halfmile Lake massive sulfides in chloritic argillite contain hydrothermal magnetite.
    Full-text · Article · Jul 2015 · Ore Geology Reviews
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