Results discusson27 Mar 2020 15:05
DISCUSSION OF RESULTS
Ferroan dolomite in wallrock and as quartz-carbonate composite chips was identified in five drill holes from MGA’s 2019 reverse circulation (RC) drilling programme at the Creswick gold project: CSR008, 010, 012, 013 and 014.
The presence of ferroan dolomite is a positive indicator of hydrothermal fluid pathways, particularly where associated with quartz vein material, and allows metamorphic quartz to be distinguished from hydrothermal quartz veins.
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 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 Dr Arne for any future RC drilling at Creswick.
Dr Arne has also observed that if the stratigraphy is consistently dipping moderately to the west there is hydrothermal alteration and associated quartz veining stratigraphically below the Dimocks Main Shale, roughly below the historical surface workings at vertical depths between approximately 50 and 120 metres. Quartz-carbonate veining appears to be associated with sandstone units in the deeper intercepts where ferroan dolomite has been recognised through staining, and so is compatible with many other central Victorian deposits where sandstones adjacent to thick shale units behave in a brittle manner during deformation to create a host for gold mineralisation. Therefore mineralisation may not be restricted to the Dimocks Main Shale as the Company initially believed.