Citation: Caritat, P.d.; McInnes, B.I.A.; Walker, A.T.; Bastrakov, E.; Rowins, S.M.; Prent, A.M. The Heavy Mineral Map of Australia: Vision and Pilot Project. Minerals 2022, 12, 961. https://doi.org/10.3390/ min12080961 Academic Editor: Michael S. Zhdanov Received: 17 June 2022 Accepted: 27 July 2022 Published: 28 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). minerals Article The Heavy Mineral Map of Australia: Vision and Pilot Project Patrice de Caritat 1, *, Brent I. A. McInnes 2 , Alexander T. Walker 2 , Evgeniy Bastrakov 1 , Stephen M. Rowins 2 and Alexander M. Prent 2 1 Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia; evgeniy.bastrakov@ga.gov.au 2 John de Laeter Centre, Curtin University, Bentley, WA 6102, Australia; directorjdlc@curtin.edu.au (B.I.A.M.); a.walker@curtin.edu.au (A.T.W.); stephen.rowins@curtin.edu.au (S.M.R.); alexander.prent@curtin.edu.au (A.M.P.) * Correspondence: patrice.decaritat@ga.gov.au Abstract: 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. Keywords: heavy minerals atlas; heavy mineral maps; National Geochemical Survey of Australia; mineral network analysis; geological setting; mineral system; mineral prospectivity; critical minerals; critical elements 1. Introduction Heavy minerals (HMs), i.e., those with a specific gravity greater than 2.9 g/cm 3 (e.g., zircon, rutile, phosphates, spinels, and oxides; see Table S1 in Supplementary Materials), generally occur in low abundance in primary igneous and metamorphic rocks [1]. Due to their relative resistance to physical and chemical weathering, many HMs can persist in the sedimentary rock record, where they can be used to determine sediment prove- nance [2]. Similarly, HMs that occur in unconsolidated sediments collected from modern catchments (watersheds) may be the only proxies available for determining subsurface geology where regolith cover is widespread. The presence or absence of particular HMs, their concentrations and distributions, or the relative makeup of the HM assemblages, can be indicative of geological processes including volcanism, metamorphism, alteration, weathering, and mineralization [1]. For example, co-occurring augite, chrome-spinel, and olivine may indicate a mafic igneous origin; co-occurring garnet, staurolite, and kyanite may indicate a metamorphic source; and presence of gahnite may indicate high-grade metamorphism of zinc mineralization [3]. Thus, particular HMs can be termed indicator minerals. Moreover, HMs are common hosts for technology critical elements, e.g., pegmatite and carbonatite minerals hosting rare earth elements (REEs) [4]. Chemical elements hosted in these particular HMs, termed technology critical minerals, are essential for a cleaner (lower Minerals 2022, 12, 961. https://doi.org/10.3390/min12080961 https://www.mdpi.com/journal/minerals