Abstract: Numerous silver-rich, galena- and sphalerite-bearing veins and stratabound lenses are located on both sides of the Yukon-British Columbia border in the Rancheria District. Some veins are within either the Cassiar Batholith or other mid-Cretaceous intrusions; some veins and lenses are near the Cassiar Batholith within early and middle Paleozoic carbonate rocks/and others are far from any exposed Cretaceous Batholiths. Green first thought that a distinctive type was defined by those associated with Lower Cambrian limestone. Gabrielse and Mulligan emphasized the well-defined stratigraphic and structural controls of those located near the Casssiar Batholith, and inferred that they were related to that intrusion. Stratabound lenses far from large intrusions are recent discoveries. Exploration geologists first considered them to be Paleozoic syngenetic/diagenetic deposits, but later exploration has revealed their epigenetic nature. No explanation has been offered for the origin of veins within the Cretacoeus intrusions.

This report describes the characteristics of the deposits, and attempts to show that they comprise a distinct type with a common genesis. If so, the deposits are younger than and unrelated to mid-Cretaceous Batholiths. They are closely related to:: steeply dipping faults with a variety of strikes, mafic dykes, felsic dykes and breccias. The deposits, dykes, faults and breccais may all be related to regionally extensive, large scale, northwest-trending, dextral transcurrent faults that were active during Late Cretaceous and Early Tertiary time.

Authors: Abbott, G.

Map Scale: 1 : 0

Citation: Abbott, G., 1985. Silver-bearing veins and replacement deposits of the Rancheria District. In: Yukon Exploration and Geology 1983, Yukon Geological Survey, Indian & Northern Affairs Canada/Department of Indian & Northern Development: Exploration & Geological Services Division.