STRUCTURE CONTROLS ON GOLD DEPOSITS IN THE CARIBOO GOLD MINING DISTRICT, BRITISH COLUMBIA, CANADA

The Cariboo gold mining district is located in central British Columbia, Canada. Recorded gold production from the area totals more than 4.0 million ounces, including an estimated 2.7 million ounces from placer mining and 1.3 million ounces from lode mining. The district consists of two dominant metallogenic series of gold deposits: quartz vein and pyrite replacement styles. The quartz vein series includes strike vein, diagonal vein, orthogonal vein, and northerly veins, while the pyrite replacement includes replacement in limestone and that in calcareous clastic rock.

The district is situated within the Quesnel Highlands on the eastern edge of the Interior Plateau, which are the remnants of rolling plateau formed initially from bedrocks lain down as the ancient North American Plate moved westwards colliding with offshore seabed and island groups. The district is situated within the Cariboo Gold Belt, part of the Omineca Belt of the Canadian Cordillera, a world-class producer of gold that has had a history of mining dating from the Cariboo Gold Rush in the 1860’s.

The district consists of a late Proterozoic and/or Paleozoic sequence of continental shelf and slope deposits developed adjacent to the craton of Ancestral North America, and includes clastic sedimentary rocks along with lesser amounts of volcanic rocks and carbonates.

Rocks of the district were subjected to an early period of ductile deformation that resulted in westward directed, asymmetrical folds plunging shallowly to the northwest. During late Cretaceous to early Tertiary time, the area was disrupted by northwest trending dextral strike-slip faults such as the Willow Fault, a major strike-slip fault in the area. The north striking cross faults are an important control for the gold vein mineralization.

The district is underlain by a northwest striking, moderately northeast dipping sequence of rocks on the steep, overturned limb of a southwest-verging antiform, which, in turn, is on the northeast flank of the Island Mountain anticlinorium. Stratigraphic position, host rock lithologies, and proximity to north-striking fault zones are important guides to the different styles of gold mineralization recognized in the district.

At least three phases of folding and fabric development occur in the district and are responsible for the major regional map patterns. Faults and shear zones developed in the district are of several generations and orientations.