Drill cuttings, or chips, from the 2019 drilling at Creswick were used for the tests. The results show ferroan dolomite in wallrock and as quartz-carbonate composite chips in five drill holes.
Ferroan dolomite is characteristic of alteration around central Victorian gold deposits and indicative of gold-related hydrothermal fluid flow.
The strong development of ferroan dolomite in some holes can further assist in delineating gold-bearing shoots in those areas.
“We are very pleased with the results of this study, which show good indications of hydrothermal fluid flow related to gold mineralisation in a number of drill holes at Creswick,” ECR chief executive Craig Brown said in a statement.
“Importantly, the variation in the results, with some areas ‘lighting up’ and others not, is potentially useful for identifying gold-bearing shoots. This underlines the significant gold exploration potential we believe exists at Creswick, where our tenement position covers approximately seven kilometres of the Dimocks Main Shale trend, of which our 2019 drilling tested only approximately 300 metres.”
As only a small proportion of the total samples from drilling at RC Creswick were reviewed for this study, the presence of ferroan carbonate elsewhere cannot be ruled out, particularly in oxide material where the staining test method used here is not effective but in which oxidised ferroan carbonates may be observed.
Given the nuggety nature of gold distribution in most typical central Victorian goldfields, reliance solely on gold assays for exploration may be misleading. While any anomalous gold will be significant in conventional assays, the presence of low values may represent false negatives that might lead to the premature downgrade of prospective structures.
Recognition of wallrock alteration independently of gold assays can be used to map the hydrothermal conduits that have potentially carried gold and provide support for mineralised structures in which gold assays are erratic. Accordingly, routine staining of RC chips to identify ferroan carbonates during logging has been recommended by the company’s consultant, Dr Arne, for any future RC drilling at Creswick.