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Biogeochemical expression of buried gold mineralization in semi-arid northern Australia: penetration of transported cover at the Titania Gold Prospect, Tanami Desert, Australia

¹ Co-operative Research Centre for Landscape Environments and Mineral Exploration, Geology & Geophysics, University of Adelaide, Adelaide, SA 5005, Australia corresponding author (email: nathan.reid{at}adelaide.edu.au
² Department of Chemical Engineering, University of Adelaide, Engineering North Building, Adelaide, SA 5005, Australia

Gold mineralization at the Titania Prospect in the Tanami Desert Region is buried by transported regolith including mixed aeolian and sheetflow deposits over palaeodrainage sediments. This prospect is the only example of discovery through significant thickness of transported regolith and therefore provides an important site for developing an understanding of geochemical pathways from buried mineralization. Plant sampling for biogeochemical analysis was conducted over this prospect in October 2005 with the aims of characterizing the expression of the mineralization and in particular what species best expressed the chemical signature of the buried mineralization. The multi-element chemical compositions of leaves or phyllodes were compared across the mineralized and adjacent ‘background’ areas as well as between adjacent plants at the same sites to directly compare the uptake properties of different plant species. The nine most widespread and abundant plant species at the prospect were sampled, of which three are of particular interest. The soft spinifex (Triodia pungens) expressed all of the key ore indicator elements (Au, As, Zn, S) and best delineated the buried mineralization. Melaleuca lasiandra and Acacia bivenosa also delineated the mineralization but their usefulness is reduced because of their more restricted distributions. Baseline elemental levels varied among species, and it is suggested that these differences largely relate to differences in rooting depth and thereby the plant's ability to access different parts of the regolith profile.

KEYWORDS: biogeochemistry, regolith, gold, spinifex, Triodia, Melaleuca, Acacia