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Molybdenite is a common sulfide hosting many trace elements. Trace elements in molybdenite from individual deposits have been widely used to constrain the source and conditions of ore-forming fluids. However, the relationship between the trace element composition of molybdenite and deposit types has not been well investigated from a large dataset. Here, simple statistics and partial least squares–discriminant analysis (PLS-DA) were used to determine whether different types of deposits can be distinguished by trace elements in molybdenite and what factors control the variations in trace element composition based on published laser ablation ICP–MS data. Molybdenite from porphyry deposits is separated from that from quartz veins, greisen Sn–W, granite vein Mo, and granodiorite Mo deposits. The former is characterized by relatively high Re, Cu, Ag, Se, Pb, Bi, and Te contents, whereas the latter has higher Ni, Co, Sn, Sb and W contents. Molybdenite from the quartz vein Au ± W deposits (Au-dominated), and porphyry Cu–Au–Mo (moderate Au) are separated from other deposits without gold due to positive correlations with Au, Sb, Te, Pb, and Bi for the former. Assemblages of Au–Sb–Te–Pb–Bi in molybdenite are thus useful to discriminate as to whether deposits contain gold and the degree of gold mineralization. Higher oxygen fugacity is responsible for the relative enrichment of W in molybdenite from greisen Sn–W deposits, whereas lower oxygen fugacity results in the relative enrichment of Re in molybdenite from porphyry Cu ± Mo ± Au and Mo ± Cu ± Au deposits. There are some limitations to using molybdenite as an indicator mineral because of the complex occurrences of elements in molybdenite, large compositional variations within a specific deposit type, and an imbalanced dataset. To develop molybdenite as an indicator mineral tool, further work should be carried out to overcome these limitations. This study provides an attempt to classify deposit types using molybdenite trace elements and has important implications for ore genesis research and mineral exploration. [ABSTRACT FROM AUTHOR]

This document is an editorial for a special issue of the journal Minerals, focusing on magmatic-hydrothermal iron (Fe) deposits and affiliated critical metals. The editorial highlights the importance of steel in national economic construction and identifies magmatic-hydrothermal Fe deposits as the main source of Fe in China. These deposits also host economic resources of critical metals such as rare earth elements (REE), niobium (Nb), cobalt (Co), gallium (Ga), and germanium (Ge). The editorial summarizes five papers included in the special issue, which provide insights into the genesis of magmatic-hydrothermal Fe deposits and their associated mineralization types. The papers discuss topics such as trace element data analysis, magnetite textures and chemistry, the role of evaporite layers, and the origin of Fe-Mn deposits. The editorial concludes by emphasizing the need for further studies on magmatic-hydrothermal Fe deposits. [Extracted from the article]

Hematite and goethite from 100 samples collected from various uranium deposits and prospects, associated alteration zones, and overlying Thelon sandstones in the Kiggavik–Andrew Lake structural trend (KALST; Nunavut, Canada) were investigated by EPMA (electron probe micro-analyzer) and LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometer) to establish discriminant geochemical features in order to constrain indicator mineral exploration for uranium. Three groups of Fe oxides and hydroxides were identified: (1) pre-mineralization—formed during lateritic weathering mainly by replacement of previous metamorphic minerals. This group is variably enriched in P, Pb, Mo, Nb, Cu, Cr, Ni, and Co. (2) Syn-mineralization hydrothermal hematite and goethite intergrown with illite, quartz, chlorite, and calcite ± siderite constituting the typical alteration assemblage associated with the KALST U mineralization. This group can be discriminated because of its enrichment in U, Ca, Mg, Al, Si, Mn, Y, ∑REE, Zr, K, S, and Sr and depletion in P, Fe, Cr, W, Sn and Ta. The flat and un-fractionated REE patterns in this group are comparable with those reported from Kiggavik U mineralized host rocks and are most likely reflecting the signature of parental uraniferous fluids. (3) Post-mineralization hydrothermal specularite and goethite, infilling the KALST host rocks fractures and dissolution pits, are mostly depleted in Mn, Co, Y, Sr, U, and ∑REE but relatively enriched in Cr, Sn, Ta, Ge, and W. Partial least squares-discriminant analysis (PLS-DA) of the geochemical data not only differentiates among different groups of Fe oxides and hydroxides in the KALST samples but also demonstrates the evolution of trace element composition of Fe oxides and hydroxides from the basement host rocks to the mineralization. The results suggest a basement source for the U mineralization in the KALST area. [ABSTRACT FROM AUTHOR]

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe(-Cu) deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore-forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite: Ni-Mn-V-Ti (Factor 1), Mg-Ai-Zn (Factor 2), and Ga-Co (Factor 3) magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe-Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore-forming fluids responsible for the Fe-Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe(-Cu) deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe(-Cu) deposits may be related to felsic magmatism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trace element of orogenic gold based on mineral associations, texture, and host rocks are studied. • Partial least squares discriminant analysis (PLS-DA), is used to characterize compositional data of gold. • Gold composition with different mineral associations are related to partitioning of trace elements. • Gold composition with different textures are linked to the changes of fluid compositions. • Gold composition with different host rocks are related to reactions of fluids with host rocks. The mineralogy and chemical composition of native gold from twenty-seven representative orogenic gold deposits were investigated using optical microscopy, electron probe microanalysis (EPMA), and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Minor elements, such as Ag and Cu, occur in solid solution, while trace elements, such as Fe, As, S, Hg, form impurities or micro inclusions in native gold. Partial least squares-discriminant analysis (PLS-DA) has identified compositional characteristics based on mineral association, gold texture and dominant country rocks. Gold grains are commonly associated with pyrite, arsenopyrite, chalcopyrite, pyrrhotite, and tourmaline in the studied orogenic deposits. Chemical variations in gold with different associated mineral assemblages are related to the partitioning of trace elements between co-crystalizing minerals and gold during precipitation. Gold inclusions in gangue minerals are discriminated from later gold in fractures based on contents of Ag, Fe, Pb, and Bi, which indicates that gold in different paragenetic stages of mineralization can be identified using its trace element signature. Gold hosted in different regional country rocks can be discriminated by Ag, Cu, Pd, Sb, and Hg, likely because of reactions of hydrothermal fluids with the regional country rocks along the fluid flow paths. [ABSTRACT FROM AUTHOR]