Control of Ore by Primary Igneous Structures, Porcher Island, British Columbia
The ore deposits at Surf Point and Edye Pass Mines, Porcher Island, British Columbia, lie in a quartz diorite stock. They are a series of auriferous quartz-pyrite veins occurring in a N. 20°E. zone along the axis of an arch of flow layers. Strong N. 30°E. shears in an adjacent to the stock aided in the enlargement of the magma chamber. The same stresses acting in the arch formed the ore-bearing structures by a series of small transverse movements involving the primary joints. Study of the internal structures gave valuable information on the form of the stock and the extension of the ore-bearing zone.