Abstract: Paleozoic and older metamorphic rocks in the Aishihik Lake and Hopkins Lake map areas (115 H/6 and 7) comprise the Aishihik Metamorphic Suite (AMS) and form a north-northwest-trending panel of rock that dips regionally to the east. The suite is divisible into a lower feldspathic quartz micaschist and marble package with a minor component of metaigneous rock and an upper package that includes black and brown quartzite, marble, metabasite and orthogneiss. Igneous rocks of three plutonic suites and one volcanic suite are present in the study area. Foliated hornblende granodiorite of the Aishihik Batholith, part of the Aishihik Plutonic Suite (APS), intruded in the Early Jurassic resulting in upper amphibolite grade metamorphism of the AMS. Relatively mafic APS plutonism evolved rapidly into more leucocratic quartz monzonite of the Early to Middle Jurassic Long Lake Plutonic Suite (LLPS). The Ruby Range Plutonic Suite (RRPS), including the Ruby Range Batholith and isolated stocks and tear-shaped plugs north of the batholith, intruded in the Late Cretaceous to Early Tertiary resulting in contact metamorphism and potassic metasomatism of the AMS. Sub-volcanic dykes and plugs that intrude the AMS are spatially associated with, and are thought to be genetically related to, Eocene strata of the Mount Creedon Volcanic Suite (MCVS). MCVS strata unconformably overlie all other rocks in the study area.

Potential exploration targets include:: massive sulphide deposits associated with black quartzite of the AMS; Cu skarn and porphyry deposits related to isolated stocks and tear shaped plutons of the RRPS; Cu-Au porphyry deposits associated with sub-volcanic plugs related to the MCVS; and mineralized east-trending quartz veins which may be related to a buried intrusion, possibly of the RRPS.

Authors: Johnston, S.T. and Timmerman, J.R.

Map Scale: 1 : 0

NTS Mapsheet(s): 115H06, 115H07

Citation: Johnston, S.T. and Timmerman, J.R. , 1994. Geology of the Aishihik Lake and Hopkins Lake Map Areas (115 H/6,7), Southwestern Yukon. In: Yukon Exploration and Geology 1993, Yukon Geology Exploration, Indian & Northern Affairs Canada/Department of Indian & Northern Development: Exploration & Geological Services Division, 93.

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