The geology of the High Lake volcanic-hosted massive sulphide deposit

摘要

The High Lake polymetallic deposit is located in the northern Slave Province, 40 km south of Coronation Gulf, N.W.T. Drilling done on four separate occasions has defined two main zones, the AB and D, with a combined estimated reserve of 5.3 million tonnes grading 4.05% copper, 2.36% zinc, 1.75 g/t gold and 31.7 g/t silver (Covello, 1994).;Felsic metavolcanic and metavolcaniclastic rocks are the dominant rock types in the AB Zone, and are associated with lesser irregular, discontinuous, mafic volcanic rock and carbonate-rich rock units. The sequence strikes north-northwest, dips steeply and is cut by north-south-striking diabase and dacite dikes.;The volcaniclastic-dominated unit hosts the chalcopyrite-rich massive and stringer mineralization in the AB Zone. The mineralization is also anomalous in zinc, silver and gold. The AB Zone is interpreted to have formed by the replacement of a porous, submarine volcaniclastic pile.;Primary morphology and facing direction of the zone are difficult to interpret due to the recrystallization of the sulphides during metamorphism, and the poor primary metal zonation of the deposit. However, the irregular shape of the mineralized zone and the erratic zones of zinc enrichment at the fringes are consistent with the interpretation that the zone was formed by the replacement of a porous volcaniclastic pile.;The hanging wall has been shown to be a zone of mass (volume) gain and the footwall a zone of mass (volume) loss. The hanging wall is stratigraphically overlain to the southeast by a flow-dominated unit that is weakly mineralized and altered. This is in turn overlain by a carbonate-rich felsic volcanic and volcaniclastic rock unit, which represents the least-altered suite of rocks in the AB Zone. The contacts of these units dip steeply to the northwest, implying that the sequence is overturned. (Abstract shortened by UMI.).