Open File 1995-03

Geology of the Goldstream Mine Area
(NTS 92M/9)

BC MEMPR Open File 1995-03

by J.M. Logan and G. Gibson

Open File 1995-03 presents a more detailed view of the geology of the area of the Besshi-type Goldstream volcanogenic massive sulphide deposit (82M/9). The geology is presented at 1:10 000 scale and augments information in Open File 1995-02, which is at 1:50 000 scale.

The geology and structure are complex. The oldest exposed rocks correlate with the Neoproterozoic Horsethief Creek Group, and near the mine, these consist of calcareous phyllite and fine grit with local intercalations of marble, micaceous quartzite and greenstone. The Index Formation of the Cambrian (?) to Devonian (?) Lardeau Group is divided into seven units. From lowest to highest, the units consist of marble and black limestone; graphitic phyllite and schist with calcareous phyllite and marble; the so-called Garnet zone, a black, cherty phyllite derived from an iron-magnesium-silica replacement/exhalative horizon; light brown calcareous muscovite-biotite schist, micaceous quartzite and siliceous phyllite; chlorite schist, amphibolite and metabasalt flows and sills; marble and calc-silicate schist; and quartz grit with laminated micaceous quartzite, calcareous grit, schist and dolomitic layers.

The Early Cretaceous Goldstream pluton consists of quartz monzodiorite and biotite granite with local megacrystic granite and aplite dikes.

Drilling has traced the Garnet zone and Goldstream horizon for nearly 6 kilometres. The massive sulphide zone is structurally above and stratigraphically below the Garnet zone. The Goldstream mine is a stratabound copper-zinc-silver deposit of the Besshi type. Potential also exists for carbonate replacement lead-zinc-sulphide deposits, gold-quartz veins and placer gold.