| Abstract: | Measurement of H+ ion and conductance of aqueous soil slurries as an exploration technique is conceptually attractive for use in exploration in Australia where large parts of the land surface are mantled by very thick leached weathering residuum. The common development of conductive horizons and the generally alkaline nature of the soils, however, raised doubts about its applicability.Tests have been conducted over a number of Australian deposits, mostly over massive sulphide deposits, e.g., Elura and Mt. Bulga in New South Wales. At Elura a totally weathered conductive zone extends down to about 100 m and the overlying soils are Red Earths, frequently calcareous; at Mt. Bulga the soils are skeletal podzols and the weathering is less intensive.At both deposits characteristic “rabbit-ear” anomalies, with a central peak in some instances, for H+ ion are recorded in surface soils. Conductance anomalous patterns are either sympathetic or mirror images of the H+ ion pattern, depending upon local conditions.At Elura there is no conventional geochemical response in the soils over part of the deposit, and there is a very strong transported Pb anomaly for a distance of about 1300 m southwest of the deposit. There are characteristic H+ ion and conductance responses over the entire orebody, and there is no H+ ion and conductance response over the transported Pb anomaly. At Mt. Bulga a clear H+ anomaly occurs over sulphides covered by 60 m of barren rock.The results demonstrate the potential usefulness of electrogeochemical techniques in Australia to detect deeply buried sulphides under conditions of extreme weathering. |
