Intrusion-Related Gold Deposit Model (IRG)
The intrusion-related gold deposit is a relatively new classification of gold deposits and is associated with granitic rocks. This type of mineral system is now well documented in the scientific literature and includes a number of important deposits in the Tintina Gold Belt in Alaska (e.g. Fort Knox 158 million tonnes at 0.8 g/t Au and Pogo 10 million tonnes at 15 g/t Au). The deposits are best developed above and surrounding small, granitic intrusions.
Schematic model of an Intrusion Related Gold System after work by Jim Lang and Tim Baker “Intrusion-related gold systems” in journal “Mineralium Deposita” volume 36.
The setting, mineralisation, vein style, pluton size and associated anomalous elements all indicate that an intrusion-related gold system is a valid exploration model for the Cuttaburra A prospect and can probably be applied more widely in the region. The mineralisation and associated anomalous elements are similar. Anomalous bismuth, tin, and tungsten are particularly indicative. The sheeted vein nature of the mineralisation at Cuttaburra is also typical of intrusion-related gold systems. The size and geometry are appropriate to the model - all of the magnetic anomalies so far tested are of approximately 1 square kilometre in size, although larger anomalies are also present. The host rocks however, are interpreted to be an extension of the sedimentary rocks hosting the major Cobar-type deposits further south.