Stavely Minerals has outlined an exciting gold prospect at its Ararat project in western Victoria after receiving highly encouraging results from recent soil geochemical sampling and rock-chip sampling at the Cathcart Hill Prospect. Soil geochemistry has defined an 800 metre-long arsenic and chromium anomaly with coincident gold anomalism consistent with a ‘Stawell-style’ gold system.
Stavely’s field personnel have been conducting extensive soil geochemical sampling programs for primary analysis using a Niton portable XRF analyser with check analysis through ALS Laboratories Brisbane. While the Niton XRF unit cannot be used reliably for analysis of gold in an exploration context unless in extremely high abundances, it has proven very effective for analysis of indicator elements.
The Niton results show a coincident arsenic and chromium soil sample anomaly confirmed by duplicate analysis by aqua-regia digestion and ICPMS determination which has also returned coincident gold anomalism. The anomaly extends over 800 metres in strike and remains open to the north and south. The current soil sample grid will be extended in both directions and a traverse of RC drilling is being planned.
The Cathcart Hill area was selected for systematic soil sampling because a number of very shallow air-core drill holes drilled in 1996 returned strong arsenic anomalism to 0.27% arsenic but without coincident gold anomalism. On review, Stavely personnel felt the air-core arsenic anomaly was the result of weathering of nearby gold-sulphide mineralization and subsequent lateral dispersion in the weathering profile.
As arsenic is more soluble and mobile in this environment than is gold, the arsenic anomaly could be expected to travel much further and provide a spatially much larger anomaly than gold would.
The weathered expression of the Stawell Gold Deposit was documented in a study by Noble et al as part of a Cooperative Research Centres project on Landscape Evolution and Mineral Exploration. The study found that arsenic, chromium and lead in the soils over the Stawell deposits showed the greatest anomaly contrasts and that the gold dispersion is less than that of arsenic – very similar to the patterns observed at Cathcart Hill.
During the soil sampling program, Stavely personnel noted abundant ferruginous float or ‘pseudo gossan’ which, upon laboratory analysis, returned strongly anomalous arsenic (to 0.45%) and gold (to 0.8 grams/tonne). It is interpreted that this material has formed as iron-rich concretions within the weathering profile and has been very effective at absorbing dissolved gold and arsenic dispersed in the water table by weathering of sulphide mineralization nearby, and that the level of arsenic and gold anomalism is highly encouraging in that context.
The Stawell Goldfield has produced more than 6 million ounces of historical and modern gold production with the modern Stawell Gold Mine having been in continuous operation since the mid 1980’s and having produced in excess of 2 million ounces.
Stavely Minerals’ managing director Chris Cairns says the company is encouraged by the scale, coherency and coincidence of the gold, arsenic and chromium soil anomaly at Cathcart Hill, in conjunction with the rock-chip gold results.
“Collectively, we believe this exciting new prospect could be the weathered surface expression of a possible ‘Stawell-style’ gold system. This anomaly is in the southern portion of the Cathcart Goldfield which had very significant historic alluvial and ‘deep lead’ gold production in the 1850s and 1860s but was not associated with any known hard-rock source, making it a very promising new exploration opportunity for us.”