The Olympic Cu-Au Province, Gawler Craton: A Review of the Lithospheric Architecture, Geodynamic Setting, Alteration Systems, Cover Successions and Prospectivity

Abstract

The Olympic Cu-Au Province is a metallogenic province in South Australia that contains one of the world's most significant Cu-Au-U resources in the Olympic Dam deposit. The Olympic Cu-Au Province also hosts a range of other iron oxide-copper-gold (IOCG) deposits including Prominent Hill and Carrapateena. This paper reviews the geology of the Olympic Cu-Au Province by investigating the lithospheric architecture, geodynamic setting and alteration systematics. In addition, since the province is almost entirely buried by post-mineral cover, the sedimentary cover sequences are also reviewed. The Olympic Cu-Au Province formed during the early Mesoproterozoic, ca. 1.6 Ga and is co-located with a fundamental lithospheric boundary in the eastern Gawler Craton. This metallogenic event was driven in part by melting of a fertile, metasomatized sub-continental lithospheric mantle during a major regional tectonothermal event. Fluid evolution and multiple fluid mixing resulted in alteration assemblages that range from albite, magnetite and other higher temperature minerals to lower temperature assemblages such as hematite, sericite and chlorite. IOCG mineralisation is associated with both high and low temperature assemblages, however, hematite-rich IOCGs are the most economically significant. Burial by Mesoproterzoic and Neoproterozoic-Cambrian sedimentary successions preserved the Olympic Cu-Au Province from erosion, while also providing a challenge for mineral exploration in the region. Mineral potential modelling identifies regions within the Olympic Cu-Au Province and adjacent Curnamona Province that have high prospects for future IOCG discoveries. Exploration success will rely on improvements in existing potential field and geochemical data, and be bolstered by new 3D magnetotelluric surveys. However, drilling remains the final method for discovery of new mineral resources.

Kinetically driven successive sodic and potassic alteration of feldspar

“…These P-T conditions approximate the alteration/mineralisation process of the high-temperature evolution of porphyry Cu systems (350–700 °C 20 ; 400–840 °C 21 ) and IOCG deposits (e.g. 500–550 °C in the Mt Isa province 7 ; >600 °C in the Gawler Craton 22 ).…”

Dynamic feldspar alteration governed by single self-evolved fluid system

“…The sealed capsules were heated to 600 °C at 2 kbar for run durations between 1 and 5 days. These P-T conditions are within the range of alteration/mineralization process of the high-temperature evolution of porphyry Cu systems (350-700 °C 19 ; 400-840 °C 20 ) and IOCG deposits (e.g., 500-550 ˚C in the Mt Isa province 7 ; > 600˚C in the Gawler Craton 21 ).…”

Iron oxide copper-gold (IOCG) deposits – A review (part 1): Settings, mineralogy, ore geochemistry and classification

“…Iron oxide-rich to iron oxide-poor Cu-Au deposits and related alteration in the Olympic Cu-Au province of the Gawler Craton are hosted by ~1850 Ma to ~1585 Ma rocks including felsic and mafic intrusions of the ~1850 Ma syn-orogenic Donington Suite (Hand et al, 2007;Reid, 2019), metasedimentary rocks of the ~1760-1740 Ma Wallaroo Group (Hand et al, 2007;Cowley, 2008), and felsic and mafic igneous rocks of the ~1600 Ma to ~1580 Hiltaba Suite and GRV. Although Meso-to Neoarchean rocks of generally medium-high grade metamorphic are widespread in basement to the west of the Olympic Cu-Au province, Archean rocks are also known within the province, represented by the low metamorphic grade Devils Playground mafic volcanics between the Olympic Dam and Prominent Hill deposits (Reid et al, 2009).…”

“…Although magmatism of the ~1633-1608 Ma syn-tectonic and arc-related St Peter Suite (Swain et al, 2008;Reid et al, 2019) is known in the Gawler Craton only from far to the west of the Moonta-Wallaroo district, it temporally overlaps the period of metallogenic event A.…”