Mortlock Project

The Mortlock Project consists of undulating agricultural country on the eastern margin of the Mortlock River between the towns on Wongan Hills and Konnongorring in the South Western Mining Division of Western Australia.

Achaean greenstones occupy a wedge shaped, north north-westerly trending zone along the western edge of the Exploration License area between the Cainozoic sediments associated with the Mortlock palaeo-drainage in the west and the Achaean granites rocks in the east. The relationship between the various granite types is unclear with evidence of widespread multiple intrusion.

Cainozoic sediments, composed dominantly of sandy clay and clay occupy a palaeo-drainage channel, part of the former Moore River drainage, the base of which is 55m below the level of the current Mortlock River. Laterite ridges and Achaean rock outcrops are surrounded by a mantle of sand with lenses of ferruginous pisoliths. These areas are particularly abundant around the Mortlock drainage divides and merge into colluvium on valley sides adjacent to the alluvium flats.

Uranium was discovered in 1955, during the sinking of water bores at Kalguddering. Dark green water was produced and nodules of green material were observed in the drilling sludge. Uranium was suspected and samples were submitted to the Western Australian Mines Department. This confirmed the mineral as identified as Autunite, a hydrated phosphate of uranium.

Subsequently, the area was inspected by a WA Mines Department geologist who confirmed the existence of a greenish fluorescent radioactive mineral in the sludge from the water producing bore and an adjacent unsuccessful bore. He noted above background radiometric responses from various localities in the immediate area.

An airborne radiometric survey undertaken during 1976 and 1977 by a previous explorer in the Wongan Hills - Goomalling district identified anomalies over Achaean granitic rocks and Cainozoic sediments between Wongan Hills and Konnongorring. Follow up ground exploration was restricted to road verges or reserves and consisted of surface sampling and drilling, logging and analyses of material from 122 holes. Due to access problems and drill rig limitations the original uranium discovery and some airborne radiometric anomalies were not tested.

During the drilling programme, uranium values between 6 and 20ppm U, at depths varying from 3 to 52m, were obtained. Uranium values of up to 20ppm U were in the Cainozoic sediments at a depth of 20m in a drill hole near the original water bore at Kalguddering and from a line of holes south west of Kalguddering, 1km from the western boundary of the License area.

A primary source for uranium within the tenement area has been demonstrated by the airborne radiometric anomalies overlying a late stage granite intrusive, in-situ uranium mineralization in the original water bores at Kalguddering and in a granite sample north of Kalguddering.

The mobility of uranium in the environment is shown by its widespread distribution in the Cainozoic sediments, uranium values peaking in the Kalguddering area. Further investigation should concentrate on confirming the extent of known primary uranium mineralization and locating favourable environments within the Cainozoic deposits for the accumulation of uranium. The potential of base metal mineralization in the greenstone sequence should not be discounted, considering the successful exploration results obtained by Dominion Mining Ltd in the same greenstone belt to the north of Wongan Hills.