Astro Resources NL (ASX:ARO) has updated the resources at the Governor Broome Heavy Minerals Project within 100%-owned Retention Licence R70/53 to total 52 million tonnes at 4.6% heavy mineral (HM) of indicated resources and 6 million tonnes at 4.5% HM of inferred resources.
The new estimates are for three areas - Governor Broome West, East, and South - which are within R70/53 held by Governor Broome Sands Pty Ltd (GBS), a wholly-owned subsidiary of Astro.
Drill hole data
The resource estimates are based on results from Astro aircore drilling carried out in February and March of 2020 as well as in 2012 and earlier aircore drilling by Metal Sands Pty Ltd from 2005 to 2007.
Drill hole data from Astro and Metal Sands comprising drill logs and analyses, from 380 aircore drill holes totalling 4,633 metres, was used to construct the ore block models (OBMs) of the HM mineralisation and to estimate the revised and new 2021 resources.
The OBM block grades were estimated by Inverse Distance Squared (IS2) interpolation from within wire-framed grade-limited mineralisation within two unconformity-separated horizontal sedimentary units.
In those areas that the relatively close-spaced drilling (120 by 120 metres grid or 160 by 120 metres grid) has clearly defined both geological and grade continuity the estimated resources were classified as indicated.
The resources were classified as inferred in those areas that, although the drilling has shown both geological and mineralisation continuity throughout the area, the drilling density has not been such to enable the verification of grade continuity.
Governor Broome Project Resources – at 2% HM lower block-cut-off grade.
Geology and mineralisation
Governor Broome HM Deposit occurs within a surficial Pleistocene sand unit, the Warren Sands (WS), and in the immediately unconformably underlying Beenup Beds (BB) of the Cretaceous Warnbro Group.
The Beenup Beds sediments are of two main facies in the area: clayey sands and organic clays.
The clayey sands contain medium- to coarse-grained, angular to sub-angular, unconsolidated quartz and minor feldspar grains.
Clay content, which is variable, tends to increase downward and generally contains between 1% and 8% of valuable HM with common accessory minerals including garnet, pyrite, and fine coal fragments.
Mineralisation that has been reported as mineral resources is based upon a minimum heavy mineral content of 2% and a maximum slimes content of 30%.
The HM assemblage averages of the order of 53% ilmenite, 6% secondary ilmenite, 3.5% leucoxene, 1.5% Hi-Ti, and 5% zircon for a total of 69% valuable HM.
Governor Broome Project location map.
Potential mining method
It has been assumed that, for potential mining of the deposits, topsoil and overburden would be removed by scrapers and the mineralisation would be mined by bulldozer feeding an in-pit slurry unit.
The slurry would be pumped to a wet concentrator to produce an HM concentrate and the waste would be returned to the mine void and covered with stored topsoil.
These deposits are within farmland and blue-gum plantations and suitable compensation would need to be addressed with the owners and occupiers before mining was carried out.