Blende Property Geology
The Blende property is a large shear-hosted vein fault system or possible Mississippi Valley type or Irish type Zn-Pb-Ag deposit on the south edge of the Mackenzie Platform, hosted by Lower Proterozoic Gillespie Group dolomite. The deposit is tabular and dips steeply, cutting bedding approximately at right angles. Mineralization occurs intermittently along a shear zone about 6 km long and up to200 m wide. Mineralization is mostly epigenetic and forms the matrix in a series of parallel brecciazones which strike east-west and dip steeply south. These mineralized breccia zones occur in the core of a large anticline and are parallel to a strongly developed axial plane cleavage which strikes ENE and dips steeply to the north and south.
The mineralization consists mostly of yellow sphalerite, which is difficult to distinguish from the host dolomite. Other sulphide minerals include galena, pyrite and minor chalcopyrite and tetrahedrite. Some syngenetic or early diagenetic mineralization has been found associated with oolites and dewatering structures. Studies by C. Godwin indicate a lead isotopic age of 1.54 Ga.
On surface, the deposit is outlined by soil anomalies up to 10,000 ppm Zn. Most geophysical methods including IP, VLF and Max-Min EM work well due to the inert nature of the host dolomite,but graphitic sediments inter layered within the Gillespie Group dolostones can create spuriousanomalies. Billiton's 1991 drilling established that the east zone and west zones are separate andthat mineralization in the west zone is regular and extends more than 400 m continuously down dip, while mineralization in the east zone is more irregular but extends continuously down dip for more than 200 m.