0361-0128/11/3964/687-26 687 Introduction THE EUCLA basin, along the southern margin of Australia, owes its distinctive landscape to a unique set of interactions involving eustacy, climate, and tectonic processes over the last ~50 m.y. (Hou et al., 2008). The result is preservation of one of the largest onshore areas of Cenozoic marine sediments anywhere in the world (Benbow, 1990; Clarke et al., 2003). The 650-km-long paleoshoreline sequence along the north- eastern margin of the basin exhibits a high degree of preser- vation and is highly prospective for heavy mineral placer deposits (Fig. 1). The extent and complexity of the paleo- shoreline deposits hampered early heavy mineral exploration. A review of exploration drilling for heavy mineral sands in the region by Ferris (1994) highlighted the need for improved understanding of the evolution of the paleoshorelines in order to identify more highly prospective regions and provide a focus for exploration. A revision of stratigraphic correlations across the basin provided new correlations relating marine-coastal sediments to the stratigraphic record of offshore sediments (Clarke et al., 2003; Hou et al., 2003b). This included a recon- struction for sequences of coastal deposition in the context of well-constrained chronology of major sea-level events (e.g., McGowran et al., 1997). Previously established models for heavy mineral concentration (e.g., Roy, 1999; Roy et al., 2000) were incorporated into the stages of coastal barrier formation and used to predict new prospective sites (Hou et al., 2003b). Aided by this perspective and results of earlier drilling, re- newed heavy mineral exploration by Iluka Resources Ltd. in June 2004 led to successful greenfield discoveries of the Jacinth (November 2004) and Ambrosia (December 2004) heavy mineral deposits (Hou and Warland, 2005). Ongoing exploration has identified 10 additional significant heavy min- eral prospects along the eastern and northern margins of the Heavy Mineral Sands in the Eucla Basin, Southern Australia: Deposition and Province-Scale Prospectivity* BAOHONG HOU, 1,2,† JOHN KEELING, 1 ANTHONY REID, 1 MARTIN FAIRCLOUGH, 1 IAN WARLAND, 3 ELENA BELOUSOVA, 4 LARRY FRAKES, 5 AND ROGER HOCKING 6 1 Minerals & Energy Division, Primary Industries and Resources SA, GPO Box 1671, SA 5000, Australia 2 College of Earth Science, Jilin University, China 3 Iluka Resources Limited, 11 Dequetteville Terrace, Kent Town, SA 5067, Australia 4 ARC National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia 5 Earth and Environmental Sciences, University of Adelaide, SA 5001, Australia 6 Geological Survey of Western Australia, Department of Industry and Resources, East Perth, WA 6004, Australia Abstract The marine Eucla basin in southern Australia is emerging as a major new heavy minerals province in Aus- tralia. Beach placers are associated with a series of partially buried Cenozoic coastal barrier sands formed along an arcuate 2,000-km-long basin margin, the trace of which is up to 320 km inland of the present coastline. The presence of high-grade deposits with dominant zircon over ilmenite and lesser amounts of rutile and leucox- ene was established with the discovery of the Jacinth and Ambrosia heavy mineral deposits in late 2004. An additional 10 heavy mineral prospects were subsequently identified and are at various stages of evaluation. The Eucla basin and its adjacent paleovalley system have a large areal extent that contains a complicated suc- cession of marine and nonmarine strata spanning a wide range of depositional environments. Four distinct con- structional phases for the development of shorelines can be recognized and correlated with major third-order sea-level events, established by others from the marine depositional record as occurring during the middle Eocene (~42.5 Ma), late middle Eocene (39–36 Ma), late Eocene (36–34 Ma), and Miocene-Pliocene (15–2.6 Ma). Prevailing westerly winds built extensive dune systems by longshore drift. Sediment movement was from west to east. Detrital zircon grains from the Ooldea and Barton barriers show a distribution of zircon age that is consistent with the Proterozoic Musgrave province to the north of the basin as the dominant primary source area of the heavy minerals, with a contribution from the Albany Fraser orogen to the west. The likelihood is that these heavy minerals have been recycled via sedimentary basins that flank the Musgrave province and in- clude the Neoproterozoic to Cambrian Officer basin and Permian to Mesozoic deposits of the Bight basin. Our current depositional model is summarized as follows: (1) initial rapid transgression and deposition of a shallow marine sand sheet subsequently overlain by shallow marine limestone during middle Eocene; (2) a major Eocene transgression and deposition of a shelf, barrier, and lagoonal shoreface marine complex during the late middle Eocene; ( 3) further transgression and highstand deposition during the late Eocene; (4) re- newed transgression of barrier, lagoonal, and possibly flooding deltaic sand blanket in the southeastern coastal plain with neotectonic uplift tilting in the western Eucla margin during Mio-Pliocene time. Each stage of reworking increased the potential for heavy mineral concentration in placer deposits. † Corresponding author: e-mail, Baohong.Hou@sa.gov.au *Corrections in proof have been made to this paper. ©2011 Society of Economic Geologists, Inc. Economic Geology, v. 106, pp. 687–712 Submitted: August 19, 2010 Accepted: February 27, 2011