Peterswald Hill18 Oct 2021 12:39
Peterswald
CRA Exploration Pty Ltd (CRA) completed a 300m line spaced aeromagnetic survey over the Robert 1:250,000 map sheet during 1996, presumably in search of discrete magnetic anomalies over kimberlite pipes. This survey indicated the presence of a large greenstone belt beneath the cover of recent sand plain and other cover.
WMC Resources Ltd Exploration (WMC) explored an area, coincident with most of the current project area, over three years from 1996-1999 (Baltis, 1997 and 1998, and Bongers and Dare, 2000). Their efforts were part of a regional initiative by WMC which involved exploration of the relatively unexplored eastern greenstone sequences of the Yilgarn Craton, some covered by Permian and Recent sediments, for gold mineralisation. These greenstone belts were attractive exploration areas, due to their unexplored nature, their gold prospectivity, and the fact that large contiguous areas within them were available, with the potential to host world class deposits. The initiative included three projects; Minigwal (Stephens, 2003), Yamarna (Berg, 2000), and Ernest Giles (Baltis, 1997 and 1998, and Bongers and Dare, 2000). The exploration successfully identified multiple gold targets within each project, and confirmed the prospectivity of each greenstone belt (Figure 2). WMC curtailed all gold exploration in Western Australia in the late 1990s and surrendered tenure over the Ernest Giles area.
WMC work at Ernest Giles included geophysics, geochemistry, and RC drilling. An aeromagnetic survey was flown over the southern half of the project area. The survey was flown at a mean height of 60m on 200m-spaced east-west lines. It was designed to provide sufficient detail to define lithological and structural target areas. Ground gravity readings were collected over the project area to better define the location of the buried greenstone belt. Geochemical sampling was completed in varying detail over the project area, with greatest density in the south. Three Yilgarn gold-camp scale target areas were defined, based on lithology interpreted from aeromagnetic data, geochemical response, and interpreted structural features: Grassy Meadows in the south, and Calanchini and East Calanchini further north. Depth modelling of the aeromagnetic data suggested cover, over the greenstone basement, of the order of 80m to 120m over the Grassy Meadows Prospect, but in the vicinity of 300m over Calanchini and East Calanchini. Seven RC holes were drilled at Grassy Meadows and one at Calanchini. Best results were 4m at 35ppb gold from 172m in Archean BIF, and 4m at 67ppb Au from 176m in mafic volcanic.
Archean basement was definitely intersected in one drill-hole (RC7), at a depth of 170m. The lithologies were BIF, basalt, fine-grained siliceous sediment, and chlorite-amphibole ultramafic. WMC’s report is unclear as to whether or not Archean rocks were intersected in RC1 and RC4 as well. One table indicates that RC1 bottomed in argillite to a depth of 204m
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