1981 Annual report EL 1358 Fergusson River

Abstract

Exploration work took the form of a regional helicopter-borne gravel sample programme together with a geochemical stream sediment sampling programme. The gravel samples consisted of the collection of 20kg of minus 4mm sized gravel particulates, and, the geochemical samples comprised 20g of minus 80 mesh sized sediment. The gravel samples were processed at the Company's mineral processing laboratory in Perth to provide a non-magnetic concentrate suitable for binocular microscope scanning for kimberlitic indicator minerals. The geochemical samples were analysed by a commercial laboratory for Co, Cu, Pb, Zn, Ni, Cr, Ag, Au, As, Nb, La, Sr, Ta, W, Sn and U. The sampling programme yielded 20 samples with an average density distribution of 1 sample per 5.4km2. The gravel sample results were reviewed for kimberlitic indicator minerals, and the geochemical results were appraised after statistical treatment to establish anomalous levels of elemental concentration. The gravel sample results failed to show any minerals pertinent to kimberlite detection, and, the corresponding geochemical sample results, although reporting two rare-earth anomalies, are interpreted as more likely to be associated with non-kimberlitic sources. Positive results which were obtained included the detection of fine grained detrital cassiterite, detrital gold, and detrital barite. Corresponding geochemical results detected low order anomalies in tin, tantalum, and base-metal elements. It is the opinion of the writer that the tenor of the available results do not offer sufficient encouragement for further exploration to be conducted for kimberlite occurrence.