The Yangibana ironstone gossans have had a varied history, originally being assessed for base metals by a prospecting syndicate in 1972.
Uranium exploration commenced in 1973 when Noranda Australia Limited (Noranda) investigated an ironstone outcrop with an elevated total count radiometric response (the Yangibana or Noranda Gossan). After limited work, Noranda determined that the radiometric anomalism was largely due to thorium and undertook no further exploration.
From 1974 to 1975, Newmont Pty Limited (Newmont) explored the area for base metals completing rock chip sampling and limited diamond drilling. Rock chip sampling results identified lead and zinc rich gossans (to 3% Pb and 1% Zn) at the Yangibana East (Noranda Gossan), Yangibana South and East Fraser’s Well prospects. Diamond drilling at the East Fraser’s Well prospect intersected limited base metal mineralisation with 0.23m at 0.65% Zn, 0.55% Pb, 5g/t Ag hosted by a carbonate-rich BIF/magnetite-muscovite schist.
In 1981, Cliffs International Incorporated examined the area initially for manganese and undertook photogeological studies that identified additional targets for base metals and uranium. 63 rock chip samples were collected and recorded anomalous lead, zinc and rare earths. Further work concentrated on four targets with little encouragement and work ceased.
Between 1985 and 1991, Challenger Mining Corporation NL and Hurlston Pty Limited were the first parties to assess the Yangibana ironstones specifically for their rare earths potential. The partners carried out programmes of rock chip sampling, mapping, petrology, ground radiometric surveying, and reverse circulation (RC) drilling. Challenger reported that the mineralised ironstone can be traced intermittently for over 25 kilometres. Surface samples from five main prospects returned rare earths values that were considered to be highly anomalous with up to 1.68% Ce, 0.77% La and 0.16% Nd. Details of analytical method or laboratory, and exact sample locations, were not provided.
In 1988, Hurlston drilled a total of 80 RC holes (3,500m) on ten of the rare earths prospects over a total combined strike length of 7 kilometres, with the majority of the holes intersecting anomalous rare earths mineralisation in the oxide zone.
Five individual one metre intervals exceeded 5% total rare earths elements (TREE), with intervals of 6.98% TREE and 5.01% TREE from Yangibana North; 6.05% TREE from Lion’s Ear; and 6.27% TREE and 5.59% TREE from Bald Hill. The widest downhole intersections at a 1% TREE cut-off were 7m and 8m at Yangibana North, and 8m at Kane’s Gossan.
Hurlston calculated average grade and bulk mineralisation tonnage for each prospect which it then totalled into an ‘indicated shallow resource potential’ of over 3.5 million tonnes at 1.67% rare earths oxide (pre-JORC estimate; Pooley, 1988).
Minor rock chip sampling and shallow auger drilling programmes were carried out by other explorers prior to Hastings acquiring its interest in the project.