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We describe a vision for a national-scale heavy mineral (HM) map generated through automated mineralogical identification and quantification of HMs contained in floodplain sediments from large catchments covering most of Australia. The composition of the sediments reflects the dominant rock types in each catchment, with the generally resistant HMs largely preserving the mineralogical fingerprint of their host protoliths through the weathering-transport-deposition cycle. Heavy mineral presence/absence, absolute and relative abundance, and co-occurrence are metrics useful to map, discover and interpret catchment lithotype(s), geodynamic setting, magmatism, metamorphic grade, alteration and/or mineralization. Underpinning this vision is a pilot project, focusing on a subset from the national sediment sample archive, which is used to demonstrate the feasibility of the larger, national-scale project. We preview a bespoke, cloud-based mineral network analysis (MNA) tool to visualize, explore and discover relationships between HMs as well as between them and geological settings or mineral deposits. We envisage that the Heavy Mineral Map of Australia and MNA tool will contribute significantly to mineral prospectivity analysis and modeling, particularly for technology critical elements and their host minerals, which are central to the global economy transitioning to a more sustainable, lower carbon energy model.

The Toodoggone district comprises Upper Triassic to Lower Jurassic Hazelton Group Toodoggone Formation volcanic and sedimentary rocks, which unconformably overlie submarine island-arc volcanic and sedimentary rocks of the Lower Permian Asitka Group and Middle Triassic Takla Group, some of which are intruded by Upper Triassic to Lower Jurassic plutons and dikes of the Black Lake suite. Although plutonism occurred episodically from ca. 218 to 191 Ma, the largest porphyry Cu–Au ± Mo systems formed from ca. 202 to 197 Ma, with minor mineralization occurring from ca. 197 to 194 Ma. Porphyry-style mineralization is hosted by small-volume (<1 km 3 ), single-phase, porphyritic igneous stocks or dikes that have high-K calc-alkaline compositions and are comparable with volcanic-arc granites. The Fin porphyry Cu–Au–Mo deposit is anomalous in that it is 16 m.y. older than any other porphyry Cu–Au ± Mo occurrence in the district and has lower REEs. All porphyry systems are spatially restricted to exposed Asitka and Takla Group basement rocks, and rarely, the lowest member of the Hazelton Group (i.e., the ca. 201 Ma Duncan Member). The basement rocks to intrusions are best exposed in the southern half of the district, where high rates of erosion and uplift have resulted in their preferential exposure. In contrast, low- and high-sulfidation epithermal systems are more numerous in the northern half of the district, where the overlying Hazelton Group rocks dominate exposures. Cogenetic porphyry systems might also exist in the northern areas; however, if they are present, they are likely to be buried deeply beneath Hazelton Group rocks. High-sulfidation epithermal systems formed at ca. 201 to 182 Ma, whereas low-sulfidation systems were active at ca. 192 to 162 Ma. Amongst the studied epithermal systems, the Baker low-sulfidation epithermal deposit displays the strongest demonstrable genetic link with magmatic fluids; fluid inclusion studies demonstrate that its ore fluids were hot (>468°C), saline, and deposited metals at deep crustal depths (>2 km). Sulfur, C, O, and Pb isotope data confirm the involvement of a magmatic fluid, but also suggest that the ore fluid interacted with Asitka and Takla Group country rocks prior to metal deposition. In contrast, in the Shasta, Lawyers, and Griz-Sickle low-sulfidation epithermal systems, there is no clear association with magmatic fluids. Instead, their fluid inclusion data indicate the involvement of low-temperature (175 to 335°C), low-salinity (1 to 11 equiv. wt.% NaCl) fluids that deposited metals at shallow depths (<850 m). Their isotope (i.e., O, H, Pb) data suggest interaction between meteoric and/or metamorphic ore fluids with basement country rocks.

Kemess South is the only Cu–Au–Mo mine in the Toodoggone district and a major Cu and Au producer in British Columbia. Porphyry-style Cu–Au–Mo mineralization is mainly hosted by the tabular, SW-plunging, 199.6 ± 0.6-Ma Maple Leaf granodiorite, which intrudes tightly folded, SW-dipping, Permian Asitka Group siltstone and limestone and homogeneous Triassic Takla Group basalt. Southwest-dipping 194.0 ± 0.4-Ma Toodoggone Formation conglomerate, volcaniclastic, and epiclastic rocks overlie the granodiorite and Asitka Group rocks. Minor Cu–Au–Mo mineralization is hosted by the immediate Takla Group basalt country rock, whereas low-tonnage high-grade Cu zones occur beneath a 30-m-thick leached capping in supergene-altered granodiorite and in exotic positions in overlying Toodoggone Formation conglomerate. Granodiorite has an intrusive contact with mineralized and altered Takla Group basalt but displays a sheared contact with unmineralized and less altered Asitka Group siltstone. The North Block fault is a deposit-scale, E-striking, steeply S-dipping normal fault that juxtaposes the granodiorite/basalt ore body against unmineralized Asitka Group rocks. Younger NW- and NE-striking normal–dextral faults cut all rock types, orebodies, and the North Block fault with displacements of up to 100 m and result in the graben-and-horst-style block faulting of the stratigraphy and ore body. Both basalt and granodiorite host comparable vein sequence and alteration histories, with minor variations in hydrothermal mineral assemblages caused by differing protolith chemistry. Early potassic alteration (and associated early-stage Cu ± Au ± Mo mineralization) is partly replaced by phyllic and intermediate argillic alteration associated with main-stage Cu–Au–Mo mineralization. Two main-stage veins have Re–Os molybdenite ages of 201.3 ± 1.2 and 201.1 ± 1.2 Ma. These mineralization ages overlap the 199.6 ± 0.6-Ma U–Pb zircon crystallization age for the Maple Leaf granodiorite. Late-stage pyrite-rich stringer veins and related phyllic alteration assemblages are cut by anhydrite-rich, carbonate-rich, and chlorite veins. Fluids and metals associated with early-, main-, and late-stage veins were probably derived principally from the same deep magma chamber as the Maple Leaf granodiorite. These magmatic-derived fluids interacted with Asitka and Takla Group country rocks and possibly with meteoric and metamorphic fluids prior to mineralization.

The Toodoggone district comprises Upper Triassic to Lower Jurassic Hazelton Group Toodoggone Formation volcanic and sedimentary rocks, which unconformably overlie submarine island-arc volcanic and sedimentary rocks of the Lower Permian Asitka Group and Middle Triassic Takla Group, some of which are intruded by Upper Triassic to Lower Jurassic plutons and dikes of the Black Lake suite. Although plutonism occurred episodically from ca. 218 to 191Ma, the largest porphyry Cu-AucMo systems formed from ca. 202 to 197Ma, with minor mineralization occurring from ca. 197 to 194Ma. Porphyry-style mineralization is hosted by small-volume (<1km super(3)), single-phase, porphyritic igneous stocks or dikes that have high-K calc-alkaline compositions and are comparable with volcanic-arc granites. The Fin porphyry Cu-Au-Mo deposit is anomalous in that it is 16m.y. older than any other porphyry Cu-AucMo occurrence in the district and has lower REEs. All porphyry systems are spatially restricted to exposed Asitka and Takla Group basement rocks, and rarely, the lowest member of the Hazelton Group (i.e., the ca. 201Ma Duncan Member). The basement rocks to intrusions are best exposed in the southern half of the district, where high rates of erosion and uplift have resulted in their preferential exposure. In contrast, low- and high-sulfidation epithermal systems are more numerous in the northern half of the district, where the overlying Hazelton Group rocks dominate exposures. Cogenetic porphyry systems might also exist in the northern areas; however, if they are present, they are likely to be buried deeply beneath Hazelton Group rocks. High-sulfidation epithermal systems formed at ca. 201 to 182Ma, whereas low-sulfidation systems were active at ca. 192 to 162Ma. Amongst the studied epithermal systems, the Baker low-sulfidation epithermal deposit displays the strongest demonstrable genetic link with magmatic fluids; fluid inclusion studies demonstrate that its ore fluids were hot (>468C), saline, and deposited metals at deep crustal depths (>2km). Sulfur, C, O, and Pb isotope data confirm the involvement of a magmatic fluid, but also suggest that the ore fluid interacted with Asitka and Takla Group country rocks prior to metal deposition. In contrast, in the Shasta, Lawyers, and Griz-Sickle low-sulfidation epithermal systems, there is no clear association with magmatic fluids. Instead, their fluid inclusion data indicate the involvement of low-temperature (175 to 335C), low-salinity (1 to 11equiv. wt.% NaCl) fluids that deposited metals at shallow depths (<850m). Their isotope (i.e., O, H, Pb) data suggest interaction between meteoric and/or metamorphic ore fluids with basement country rocks.

The syenitic Murdock Creek intrusion, of late Archean age, lies within one of the major lode gold camps of the world, at Kirkland Lake, Ontario. There is a strong spatial association between syenitic intrusions, gold mineralization, and carbonatization. Hydrothermal fluids that carried the gold had an unusually high oxygen fugacity ($f_{o_{2}}$). Notwithstanding a wide range in rock compositions within the intrusion (from clino-pyroxenite to alkali-feldspar syenite), clinopyroxene and biotite have consistently low Fe/(Fe + Mg) and high$Fe^{3+}/(Fe^{2+} + Fe^{3+})$ratios. These compositional features indicate a deficiency of$Fe^{2+}$in the magma during crystallization. Together with the presence of abundant, early-formed magnetite and titanite, this is interpreted to result from an intrinsically high magmatic$f_{o_{2}}$that remained constant during pluton evolution ($f_{o_{2}} \\approx 10^{-12} bars$). Mineral compositions, proportions of crystallizing mineral phases, and textural features indicate that the pluton formed from a single pulse of already-evolved syenitic magma that fractionally crystallized in situ under low water pressure at mid-crustal depths. The intrinsically oxidized nature of the pluton implies an oxidized source region such as metasomatized upper mantle where partial melting occurred.$CO_{2}$-rich fluid or melt was the likely agent for metasomatism. Dissolution and transport of gold is favored by high$f_{o_{2}}$in the fluid phase. The high$f_{o_{2}}$of the syenitic magma suggests a common genetic link between magma generation,$CO_{2}$represented by \"carbonatization, and gold-bearing fluids.

The Murdock Creek intrusion, immediately southwest of Kirkland Lake, Ontario, in the southern part of the Abitibi belt, is a member of a suite of late Archean ( $\\approx$ 2680 Ma) syenitic intrusions located within and adjacent to the Kirkland Lake-Larder Lake fault zone (KLF), which host virtually all of the gold mineralization in the Kirkland Lake camp. An early crystallizing mafic margin consisting of clinopyroxenite, meladiorite, melamonzodiorite, and melasyenite encloses an extensive felsic core of alkali-feldspar syenite. A coeval hornblendite unit with lamprophyric affinities, intrudes throughout the pluton and most closely approximates the mantel-derived liquids which differentiated to produce the suite of syenitic intrusions and possibly potassic alkaline extrusive rocks of the Timiskaming Group. The intrinsically oxidized nature of the pluton suggests a genetic link with gold mineralization in the Kirkland Lake camp. (Abstract shortened by UMI.)