Nb-rich trachytes from Virginia, shoshonite from Colorado and high-K dacite from the Bolivian Andes contain diverse suites of native metals and alloys. Virginia trachytes are differentiates of mafic within-plate magmas derived from oceanic island basalt (OIB)-type mantle sources in the post-orogenic extensional regime of the Appalachian mobile belt. Colorado shoshonite and Bolivian dacite were produced via crystal fractionation of Fe–Mg silicates from trachybasalt and basalt magma, respectively, derived from subduction-related mantle modified by either crustal contamination (both regions are underlain by thick, mature continental-type crust) or recycling of marine sediment. Metal assemblages include refractory metals (Pt with minor Fe and Cr, native W, Co–W and Fe–W alloys), Cu–Ag–Au alloys, chalcophile metals (Cu–Sn alloy, native Cu and Zn) and associated sulfides (galena). Textural evidence (metals occur as inclusions in phenocrysts, high temperatures of their formation, etc.) and compositional features of metallic phases suggest their magmatic origin. Metal-rich magmas (both mafic and differentiated) transport metals in convergent and within-plate tectonic settings and deliver ore metals to the oxidized porphyry and epithermal environments in the upper crust.

—Here we report results of microforms’ studies of native gold and its alloys in igneous rocks, modified to varying degrees by secondary processes. We discuss the composition and occurrence of both the deep-seated magmatic gold-bearing alloys and the products of their transformation under conditions of the upper Earth’s crust. Gold-bearing Kamchatka adakites and ankaramites, Ildeus massif mafic-ultramafic intrusions and adakites from the Stanovoy fold system as well as dacites from the Bolivian Andes were formed during melting of either the suprasubduction mantle wedge or the subducted oceanic crust. In depleted peridotites from the Avachinsky Volcano in Kamchatka as well as suprasubduction ophiolites from Polar Urals, Eastern Sayan and the Western Mediterranean Betic–Rifean belt, the gold-bearing mantle was hybridized by subduction-related melts and high-temperature fluids. Volcanic rocks associated with the Lesser Khingan Fe–Mn deposits and Zolotaya Gora Au deposit in Southern Urals as well as Taragai ultramafic rocks in the South Khingan Range display subduction-related geochemical characteristics. Gold-bearing trachytes in the Virginian Appalachians (USA) represent felsic differentiates of mafic intraplate magmas. We propose that one of the principal forms of gold transport into the upper crustal environments is represented by Cu–Ag–Au alloys, which precipitated from mantle-derived silicate melt enriched in chalcophile and siderophile elements. Such Cu–Ag–Au alloy-rich magmatic rocks can either constitute primary sources of precious metals in the mantle-crust system or serve as geochemical precursors to the formation of native gold assemblages in epithermal and mesothermal ore deposits. Presence of magmatic gold particles in subduction-related igneous rocks and mantle restites hybridized by subduction-derived melts and high-temperature fluids suggest the existence of gold-rich horizons in the Earth’s mantle at depths comparable to typical depths of generation of primary convergent zone and some within-plate magmas.

The Ildeus mafic–ultramafic complex represents plutonic roots of a Triassic magmatic arc tectonically emplaced into the thickened uppermost crust beneath the Mesozoic Stanovoy collided margin. The mafic–ultramafic complex cumulates host Ni-Co-Cu-Pt-Ag-Au sulfide-native metal-alloy mineralization produced through magmatic differentiation of subduction-related primary mafic melt. This melt was sourced in the metal-rich sub-arc mantle wedge hybridized by reduced high-temperature H-S-Cl fluids and slab/sediment-derived siliceous melts carrying significant amounts of Pt, W, Au, Ag, Cu and Zn. Plutonic rocks experienced a pervasive later-stage metasomatic upgrade of the primary sulfide–native metal–alloy assemblage in the presence of oxidized hydrothermal fluid enriched in sulfate and chlorine. The new metasomatic assemblage formed in a shallow epithermal environment in the collided crust includes native gold, Ag-Au, Cu-Ag and Cu-Ag-Au alloys, heazlewoodite, digenite, chalcocite, cassiterite, galena, sphalerite, acanthite, composite Cu-Zn-Pb-Fe sulfides, Sb-As-Se sulfosalts and Pb-Ag tellurides. A two-stage model for magmatic–hydrothermal transport of some siderophile (W, Pt, Au) and chalcophile (Cu, Zn, Ag) metals in subduction–collision environments is proposed.

Iron and iron–manganese deposits form three closely spaced clusters within the Lesser Khingan Range of the Russian Far East. Fe-Mn mineralization is hosted in Vendian–Cambrian carbonates and composed of magnetite, hematite, braunite, haussmanite, rhodochrosite and pyrolusite. The iron–manganese ores are closely associated with explosive intermediate–felsic breccias, magnetite-rich lavas, dolerites and mineralized lithocrystalloclastic tuffs. Magmatic rocks display both concordant and discordant relationships with Fe-Mn mineralization and contain abundant xenoliths of host carbonates. Both magmatic rocks (with the exception of Nb-enriched dolerites) and Fe-Mn ores are characterized by variable enrichments in large-ion lithophile and light rare earth elements and strong depletions in high-field strength elements compatible with the broad subduction setting for explosive volcanism and associated hydrothermal Fe-Mn ore mineralization. Nd-Sr isotope systematics suggest contamination by both ancient and juvenile continental crust and the involvement of recycled pelagic sediment in the formation of Fe-Mn deposits in the Lesser Khingan Range of the Russian Far East.

The activity of polyvalent elements in the geochemical processes is to a considerable extent determined by the valence state. A change in the valence is dependent on many factors, but the redox conditions of the medium where magma is generated are considered the main factor. The ratio between divalent and trivalent iron in magmatic rocks is a reliable and an accessible indicator of the redox conditions that determine a whole set of mineralogical, geochemical and physical parameters including ferruginosity of dark-colored minerals, the ore mineral (magnetite–ilmenite) composition, the weight of the ore fraction, and magnetic susceptibility. Based on the above parameters, the zones are distinguished where magmatic rocks of the magnetite and ilmenite series are developed in the Sikhote Alin Orogenic Belt. All known tin and tungsten deposits and occurrences in the Sikhote Alin are confined to the ilmenite series (the axial zone of the belt). The ilmenite rock series are framed by the magmatic rocks of the magnetite series; the epithermal gold–silver and copper–porphyry deposits are associated with these rocks.

The Paleozoic volcano-sedimentary rocks within the structural basement of the horst-and-graben system of the Catalan Coastal Ranges (CCR) are composed of black shale, volcaniclastic sediments, lava flows, sills and lithocrystalloclastic tuffs. Paleozoic sediments are depleted in high-field strength elements (HFSE) such as Nb, Ta, Zr, Hf and Ti, suggesting their accumulation within the Andean-type active continental margin environment. Volcanic rocks within the Paleozoic CCR sequence belong to shoshonitic and high-K volcanic series and are enriched in Cs, Rb and Ba and depleted in HFSE, which is consistent with their derivation from metasomatized (possibly through deep recycling of pelagic sediments) subduction-related mantle source. The presence of sills (sill-sediment complex) suggests that Paleozoic basement of the CCR was formed within the rifted active continental margin or an arc-back-arc basin system akin to the modern Western Pacific subduction configuration. This complex volcanic terroir hosts world-class wines of the Priorat DOQ region. The presence of framboidal pyrite and magnetite, siderite, sphalerite xenotime, (La–Ce–Nd)-monazite, zircon and baddeleyite, as well as cuprite, tenorite and cupriferous and native silver in volcanic-derived black shale (and consequently in the world-famous “llicorella” soil overlying it) may have had dramatic effects on wine quality and sensory characteristics. These mineral features, together with strong enrichment of Priorat shale in Au, Ag and, to a lesser extent, Pt could have pronounced effects on (1) rates and specific types of chemical reactions; (2) plant metabolism; (3) response to nutrient components and (4) determination of grape flavor. Volcanic wine terroirs, such as the Priorat DOQ region, are special geologic environments for wine growth, capable of producing unique wine aromatic and gustatory characteristics.