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WIM 150 |
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Victoria, Vic, Australia |
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Ti Zr
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The WIM 150 heavy mineral sand (HMS) deposit is located in the southern margin of the Tertiary Murray Basin, approximately 18 km south-east of Horsham in south-western Victoria, Australia.
The Murray Basin is an approximately circular depression covering and area of around 300 000 sq. km filled with up to 600 m of Palaeocene to Quaternary sediments unconformably overlying Palaeozoic to Mesozoic basement.
The lowest unit is the Palaeocene to Oligocene Renmark Group composed of fluvial and lacustrine gravel, sand, silt and clay, with large accumulations of sub-economic lignite. In the eastern part of the basin the Renmark Group sequence is overlain by further fluvial to lacustrine sediments of the Miocene to Pliocene Wunghnu Group. Equivalents to the west comprise bryazoan limestone and marls of the Murray Group, grey-green clays of the Bookpurnong Formation, the carbonaceous Geera Clay and the overlying Pliocene marine Parilla Sands.
The Parilla Sands forms a near continuous unit across the western part of the basin and is the host to the Murray Basin HMS mineralisation. A thin, virtually continuous, veneer of Quaternary clay is draped over the Parilla Sands. Recent rivers have eroded the Quaternary into the Parilla Sand, and redeposited fluvial accumulations. Quaternary dunes are widespread in the central part of the basin.
HMS are widespread in the Parilla Sand across the south-western part of the basin, mostly low grade and at uneconomic depths. The better resources occur within a 240 km long arcuate band extending from 10 to 15 km NW of Birchup, to around 75 km SW of Horsham. WIM 150 lies in the south-western part of this arc, close to the basin margin basement outcrop a few km to the south-east. The northern tip of the arc tapers agains the western margin of a thin north-south aligned basement ridge. The arc broadens and is composed of broad lobate deposits, which thicken and increase in grade to the south-west. The WIM 150 is the largest and best known of these deposits.
At WIM 150 the Parilla Sand conformably follows the Geera Clay above a weathered contact representing a depositional hiatus, and varies from 5 m in thickness to the south, to 22 m in the north. It is composed of very fine sand to silt with white mica flakes and displays low angle undulatory laminations to hummocky cross-stratification, believed to be the product of major storm activity in an offshore environment, below the fair weather wave base. Minor lenses up to 50 cm thick, characterised by abundant angular quartz granules interlaminated with fine sand laminae, are distributed throughout, occuring as low angle cross-stratified swales and rare high angle cross-bed sets of limited lateral extent. The top few metres of the Parilla Sand are commonly medium grained sands, also exhibiting low angle undulations to hummocky cross stratifications, plane laminations, with minor quartz granule lenses. The HMS concentrations are almost completely restricted to the very fine sand facies.
The overlying Quaternary veneer comprises 2 to 8 m of brown to grey sandy clay which drapes over the Parilla Sand with little variation in thickness.
The deposit is composed of multiple, flat lying, vertically stacked, conformable lenses of HMS, seperated by weakly mineralised or barren sand. Individual HMS lenses range in thickness from a few cms to 2 m and are laterally traceable for up to several hundred metres with grades of up to 40% total heavy minerals. In common with the host sands, the lenses exhibit internal undulatory lamination and hummocky cross stratification.
The envelope enclosing all of the heavy mineral lenses varies from 6 m in thickness in the south to 15 m in the north, commonly overlain and underlain by barren sands that are 1 to 6 m and 1 to 2 m thick respectively. The HMS envelope shows a high degree of continuity and has the shape of a sheet-like body with a lobate outline. Individual lobes may be up to 10 km long and 3 km wide. The central higher grade zone has a low grade internal belt which corresponds to a belt of thicker sands, giving the deposit a "J" shape in plan view.
The bulk of the mineralised sands are soft, only weakly compacted to the consistency of a stiff soil, with induration only evident at the top and botton of the Parilla Sand. Induration in the HMS mineralisation is rare, with iron oxide or kaolinite-gibbsite cement.
The heavy mineral (HM) assemblage ranges from 38 to 1000 µm in size, with the valuable minerals in the finer range. The heavy mineral composition remains consistent across the deposit and is independant of the total HM grade. The HM composition comprises: ilmenite 31.6%; zircon 13.3%; leucoxene 11.6%; rutile & anatase 8.7%; monazite 1.4%; xenotime 0.4%; goethite 6.7%; spinel 0.1%; light heavies (porous iron oxides, tourmaline, sillimanite, andalusite) 23.8%; others 2.4%.
The main heavy minerals ilmenite, leucoxene, rutile and zircon vary in modal size from 40 to 49 µm, while monazite and xenotime have a modal size of 35 µm. The gangue sands are fine quartz with minor mica flakes with a matrix of very fine quartz, kaolinite, goethite and mica/illite. The quartz grains are are equant and subangular wirh conchoidal fracures and a modal size of 75 µm. The sands are immature, although the component minerals tend to be in hydraulic equilibrium.
The deposit covers an area of 220 sq. km, with a long axis of 26 and has a resource of 4.9 Gt @ 2.8% HM with 31.6% ilmenite, 13.3% zircon, 8.7% rutile & anatase, 11.6% leucoxene, 1.4% monazite (Williams, 1990). Other estimates have been quoted at >1 Gt @ > 3% HM, and 753 Mt at 4.0% HM (Australian Zircon, 2008).
The most recent source geological information used to prepare this decription was dated: 2008.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Klingner, D. and Standing, C.A., 2016 - WIM150 mineral sand deposit, Murray Basin, Australia: geology and mineral resources: in Trans. IMM (incorp. AusIMM Proc.), Section B, Appl. Earth Sc. v.125, pp. 121-127.
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Williams V A 1990 - WIM 150 detrital Heavy Mineral deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v2 pp 1609-1614
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