DEPOSIT TYPES
The Blanket orebodies comprise up to 10% of precious metals. The Blanket mineralisation is hydrothermally emplaced and associated with the regionally developed D2 deformation characterised by areas of high strain wrapping around relatively undeformed remnants of the original basaltic flows. Wider orebodies occur within the more ductile tensional high strain areas. Two main types of mineralisation are recognised at Blanket, namely Disseminated Sulphide Reefs (DSR) and quartz-filled reefs and shears. A third type of mineralisation may be evidenced in the form of auriferous sulphide minerals as a replacement of the iron-rich minerals along the hinges of the folds in BIF.
MINERALISATION
Mining at Blanket occurs over a 3 km strike that includes from north to south, the deposits of Lima, Eroica, Sheet, AR Main, AR South, Feudal, Blanket Section (Blanket 1 to Blanket 6) and Jethro. The main Blanket underground workings are connected to Lima by a 2 km long haulage which follows the strike of the main fabric.
Wall rock alteration typically comprises silica-pyrite-muscovite within a broader carbonate alteration halo. Quartz-carbonate altered rock forms the most commonly recognised alteration assemblage. Gold is deposited at crustal levels within and near the brittle-ductile transition zone at:
• depths of between 6 km and 12 km;
• pressures between 1 and 3 kilobars; and
• temperatures between 200ºC and 400ºC.
The d ........
