Regional Geology and Mineralization of the Big Salmon Complex (104n Ne and 1040 Nw)

Reconnaissance mapping in the Big Salmon Complex in northwestern British Columbia (104N NE and 1040 NW, Figure la) was initiated in 1997 to test long-standing correlations (e.g. Mulligan, 1963) with rocks of the Yukon-Tanana Terrane (formerly Yukon Group) in southern Yukon (Figure lb). Such correlations are especially important t?om an economic standpoint (e.g. Nelson, 1997) because of the recently recognized potential for volcanogenic massive sulphide deposits in these rocks following discovery of the Kudz Ze Kayah, Wolverine and Fyre Lake deposits in the Yukon. A single traverse of the Big Salmon Complex by Nelson (1997) served to highlight similarities between stratigraphic elements in northern British Columbia and those at the Wolverine deposit. This report provides details on the stratigraphic and structural setting of the Big Salmon Complex, as well as mineral potential in light of strengthened correlations with YukonTanana Termne (YTT) in the Yukon. Mapping was conducted over a six week period in July and early August. More than 90% of the region is below treeline in broad fluvially-modified glacial valleys occupied by the lower Swift River and its tributaries (Plate 1). Although fluvial and glacial deposits are tens to (?)hundreds of metres thick in the main Swift River valley, above an elevation of about 900 m, there is only a thin veneer of alluvium, colluvium or organic debris and bedrock exposures are common. Outcrop is much more abundant than indicated on previous maps. Most road construction, unless following valley bottoms or perched glacial terraces, exposes semi-continuous outcrop at elevations above 900m. Thus the deep roadwork along the new Alaska Highway Route and burrow pits (circa 1988) and access roads to mineral properties both north and south of the highway, provide good sections through stratigraphy. Logtung and Pure Silver access roads are washed out at 6.5 km and 5 km respectively and the Arsenault road is washed out at the Swift River, but all are passable by foot.