Sorby Hills Mine, Sorby Hills, Wyndham-East Kimberley Shire, Western Australia, Australiai

Regional Level Types
Sorby Hills Mine	Mine
Sorby Hills	Group of Hills
Wyndham-East Kimberley Shire	Shire
Western Australia	State
Australia	Country

Located 55 km north east of Kununurra.

Lead-silver deposits. Located in Western Australia but close to the Northern Territory border. Reports of surface lead-silver caused Aquitane Australia Minerals Pty Ltd to explore the area finding the Discovery Hill Gossan. Further drilling produced disappointing results. However, it gave the company encouragement and they tried Sorby Hills to the east and north-east where 13 mineralised pods were found, up to 7 metres thick, striking north-south over 8 kilometres.

These were explored in detail between 1974-1977. Further underground testing in 1978-1979 failed due to flooding. Exploration again took place in 1981-1984 determining a total of 16.42 mt @ 5.25% Pb, 0.6% Zn and 56 g/t Ag. KBL Mining plans to conduct test mining from shallow open pits in 2014.

The deposits are hosted in the onshore portion of the Bonaparte Basin, in particular the Pincombe Inlier within this basin. The mineralised pods are found in four areas along north north-east trends parrallel to the main Halls Creek Mobile Belt faults. The largest pod is called Sandy Creek.

The stratigraphy at Sorby Hills shows:
1. Antrim Plateau Volcanics, 150 metres thick, of tholeiitic basalt outcropping on the western side of Sorby Hills.
2. Unconformity then the Cockatoo Group, subdivided into the 300 metre thick Kellys Knob Sandstone, and the 100 metre thick Abney Sandstone of green and pink siltstone and medium grained arkosic arenite with pebbly bands and pyrite nodules.
3. Buttons Formation, 300 metres thick, of brown and light grey massive crystalline dolomite, dolomicrite and minor siltstone, with a sandy base, formed in a shallow marine environment.
4. Disconformity, then the Burt Range Formation, subdivided into the 100 metre thick Sorby Dolomite Member of unfossiliferous vuggy dolomite and dolomitised siltstone; the D2 Unit, 15-20 metres thick of breccia and containing most of the mineralisation; D3 Unit, 80 metres thick, of dolomite siltstone and shale; and the Gooseneck Member, 50 metres thick, of unaltered sandy dolomite and siltstone.
5. Milligans Formation, 300 metres thick, of black shale.

The pods can be divided into:
1. Pods A to G, making up half the strike length, within the D2 Unit breccias, occurring in palaeo channels cutting through the underlying Sorby Dolomite Member.
2. Pods H, I and J, also found in the D2 Unit, but controlled by Precambrian palaeo highs reflected as a relatively flat anticline.
3. Beta Pods, in the D3 Unit, associated with tensionally collapsed breccia, or found locally throughout the whole of the Burt Range Formation.
4. Alpha Pod, is hosted by the D3 Unit, is the most northerly of the deposits, and associated with tectonic and sedimentary breccia along the faulted margin of the Pincombe Inlier.

The dominant mineral is galena, lesser finer grained sphalerite, and minor pyrargyrite, tetrahedrite-tennantite, and bournonite, all mainly found included in the galena. Marcasite, pyrite, calcite and crystalline dolomite is also commonly found as gangue minerals. The only zoning is a preference for Zn at the lower levels and along the margins of the pods.

Galena occurs through an area 1.5 metres thick and is described as being very abundant. It occurs as coarse grained cubes within a silty breccia matrix, as coarse grained octahedral galena filling fractures, or as matrix in tectonic breccia. Minor colliform sphalerite may also fill the fractures. Minor areas are dominated by sphalerite with some galena, lining fractures and solution cavities cutting earlier breccia and other structures. Good galena specimens appear possible from the location but are yet to be seen.

Other Regions, Features and Areas containing this locality

References