Mud Tank Zircon Field, Alcoota Station, Central Desert Region, Northern Territory, Australia
|Latitude & Longitude (WGS84):||23° 0' 45'' South , 134° 16' 10'' East|
|Latitude & Longitude (decimal):||-23.01252,134.26967|
|Köppen climate type:||BWh : Hot deserts climate|
The Mud Tank collecting area is 6 km from Plenty Highway. This is a popular collecting spot, mostly for large zircon crystals, in a carbonatite. The Mud Tank carbonatite comprises at least four pipe-like bodies tending in a northeast-southwest direction. The outcrops form a series of low hills spread over 5km of which the most northerly is the most prominent. The most northerly was being mined for vermiculite recently, with collectors allowed to fossick on the dumps still.
Mud Tank is listed in many publications as Harts Range or Harts Range district but is in fact in the far eastern end of the Strangways Range, located on Alcoota Station.
It should be noted that many refer to the Strangway Ranges but the Geoscience Australian and the Northern Territory Government lists it as Strangways Range - see for example "Strangways Range region NT 1:100 000 geol map commentary - Sheets 5651/5751.
The zircon field is 7.7 kilometres east from the Gemtree caravan park, turn south at the Mud Tank Bore and head 6 kilometres south-west. Most zircons found are orange to amber to pale brown, but also to a lesser extent pink, purplish, colourless, yellow, part-coloured, as double terminated small crystals, and chips. There are two closely spaced locations being Specimen Hill, and Mud Tank Hill. The former contains larger zircon crystals, but are often internally flawed. Some smaller crystals can be cutting quality. Waterworn crystals can be found in low lying areas between the two locations. Zircons are found by digging down to the gravelly wash layer, containing zircons, apatite nodules, mica chips, and rubble. At the western side the wash layer is virtually at the surface, while the eastern side it is about one metre below the surface.
Apatite is found as big, fractured, pale green or brown lumps. Magnetite blackish, and has generally oxidised to martite, a metallic lustre, and non magnetic. Zircon crystals may be found within the magnetite. Pink microcline and small garnets occur on the western side of the main diggings. Moonstone can be found on a low hill between Specimen Hill and the main diggings. Vermiculite as a golden soft flaky mica is common.
As some people camp on the field the entire winter, the amount of zircons available has gradually decreased over the decades, although a day of hard work is still guaranteed of producing a small handful of specimens. Fossicking tours to the site is conducted by the Gemtree caravan park, which can also arrange the cutting of suitable stones for a fee.
19 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
541 - 1000 Ma
|Mud Tank Carbonatite|
Age: Neoproterozoic (541 - 1000 Ma)
Stratigraphic Name: Mud Tank Carbonatite
Comments: igneous carbonatite; synthesis of multiple published descriptions
Lithology: Igneous carbonatite
Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia). 
Crohn, P.W. & Moore, D.H., (1984) The Mud Tank Carbonatite, Strangways Range, central Australia. BMR Journal of Australian Geology and Geophysics 9:1:13-18. Bureau of Mineral Resources, Geology and Geophysics, Canberra.
Thompson, D. (ed.) (1986), A Guide to Fossicking in the Northern Territory, Northern Territory Geological Survey, Northern Territory Department of Mines and Energy, 2nd ed. 73p, 1986