The mineralization at Musselwhite can be classified as an Iron Formation hosted gold deposit. Typically, gold in these deposits occurs in cross-cutting quartz veins and veinlets or as fine disseminations associated with pyrite, pyrrhotite, and arsenopyrite hosted in iron formations and adjacent rocks within volcanic or sedimentary sequences (McMillan 1996).

Mesothermal veins.
Mineralization is predominantly hosted within meta-chemical sediments (banded iron formations) and in particular within garnet-magnetite-grunerite facies meta-banded iron formations (locally termed the Northern Iron Formation). The location of mineralization is controlled by the intersection of shear zones and folded meta-banded iron formations. These geological controls result in mineralized shoots, which plunge at approximately 15 degrees to grid north, have a down dip extent of up to 150 metres, down plunge continuation in excess of 1.5 kilometres, and across-lithology width of up to 10 metres. Mineralized zones are characterized by abundant pyrrhotite, quartz flooding and, rarely, visible gold.

Musselwhite utilizes both conventional and modified Avoca mining methods depending on the access available for that retreat. Retreats without a secondary access are mined utilizing modified Avoca. With modified Avoca, all activities are completed from the retreat drive. The fill is placed from the retreat end and therefore, once the panel has been filled there is a requirement to remove some fill (void pull) to 1. Provide void space for the next blasting cycle and 2. Prevent fill from mixing with the ore causing dilution.

With increasing depth, blast sizes have had to be reduced to control unplanned dilution.

In a set of trials at Musselwhite mine beginning in late 2016, Goldcorp tested a new mining method to reduce dilution in its production stopes with Orica’s WebGen 100 wireless detonators.

Since the case study blast, Musselwhite has implemented the TRP method in several areas of the mine where excessive dilution is being experienced.

Temporary Rib Pillar AVOCA
The Temporary Rib Pillar (TRP) mining method was developed by Orica to take advantage of fully wireless blast initiation.

With the TRP method, a temporary pillar, located at the backfill/ore interface, as well as a slot are drilled in the next panel to be mined. The entire panel is loaded in one loading operation, the TRP is primed with WebGenTM 100 and the Mass Blast is primed with i-konTM.

The Mass Blast is fired and mucked out leaving the T ........

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