Transported cover in northwestern Victoria, Australia — An impediment to geochemical exploration for gold

At the Kewell and Wildwood prospects in northwestern Victoria, where transported cover (20–130 m depth) masks gold mineralization, the use of partial extraction analyses of regolith, soil and pedogenic carbonate-dominant soil was assessed. Arsenic, Au and Li from 50 elements analyzed are associated with mineralization and are dispersed vertically for 5 m into the cover. However, these elements do not reach the surface, and so preclude the use of the surface partial extractions even though the initial trial of a proprietary Bacterial Leach extraction of soil predicted mineralization in the shallow cover regions (< 20 m) based on hypergeometric statistical evaluation. Near-surface sampling and any combination of partial extractions are not a viable approach for exploration through cover in northwestern Victoria. The cover is too thick and the provenance of the sediments has more influence on variation in geochemical abundance than dispersion from any underlying mineralization.

► No consistent successful geochemical surface expression.
► Hydromorphic dispersion for As and Li.
► Dispersion does not go through transported cover to the surface.
► The interface identifies a zone that may be targeted for future geochemical exploration.