Mapping by the Geological Survey of Western Australia (GSWA) in 1962 identified the gossan outcrops which are now known as the Onedin and Sandiego prospects. Pickands Mather explored for base metals over the area south of Halls Creek from 1963 to 1972. Between 1972 and 1977 Kennecott pegged tenements over known Cu-Pb-Zn-Ag gossans at Koongie Park, around the Onedin and Sandiego areas, and undertook geological and structural mapping, rock chip and soil sampling, diamond and percussion drilling. From 1978 until 1979 Newmont continued to drill test known mineralisation and magnetic anomalies coincident with electromagnetic (EM) conductors along strike of known mineralisation. Extensive trenching, percussion and diamond drilling, detailed EM, ground magnetic surveys, and low-level aeromagnetic surveys failed to locate significant extensions to base metal prospects. In 1980, North Broken Hill concentrated on testing the supergene enriched zone of the base metal mineralisation at the Sandiego prospect. From 1983 to 1988 Asarco carried out RAB drilling, including limited work on supergene gold potential at Sandiego. From 1988 to 1989 RTZ Mining / BP Minerals in JV with Asarco continued testing for gold potential by re-assaying split core samples for gold. This work located several loworder gold anomalies in the Sandiego area.
A group of six tenements were initially purchased by AAR from RTZ Mining in March 1990, with three additional mining leases pegged and granted in 1994. The six originally granted mining leases were explored by AAR in joint venture with Billiton Australia (now Anglo Gold) from 1989-1994. Billiton earned its equity but was forced to sell their interest to AAR under a pre-emptive rights clause, when Acacia Resources purchased all of Billiton’s assets in Australia in 1994. Billiton undertook aeromagnetic and radiometric surveys. Minor geochemical sampling done during this time produced modest gold bearing results. In 1995, Lachlan Resources (a subsidiary of Barrick Gold) signed a JV agreement over the area and continued exploration until 2002. During 1996 and 1997 Lachlan and AAR carried out extensive resource definition type drilling and developed geological and structural interpretations for both Onedin and Sandiego base metal deposits. AAR obtained 100% ownership of the project due to the withdrawal of Lachlan Resources from the Joint Venture in 2002.
In 2006, following a substantial improvement in base metal commodity prices, AAR commenced its first drilling program in its own right. AAR then established a maiden mineral resource estimates for the Sandiego and Onedin deposits reported in conformance with the JORC Code (2004). In October 2008 AAR completed a study on the economics of underground mining of the Sandiego deposit. Further drilling occurred in 2007-2009 with subsequent resource updates reported in conformance with the JORC Code (2004).
Some 245 RC and diamond drill holes encompassing 50,417 m have been drilled on the project by AAR. This effort focused on resource, metallurgical and geotechnical drilling at the Sandiego and Onedin base metal deposits. Since 2011 AAR focused on gold exploration, with little exploration for base metals occurring on the property.