string(10) "[Minerals]"

An Evaluation of the Strata-Bound Base Metal Potential of the Middle and Upper Purcell Supergroup, Southeast British Columbia

Lead Researcher(s):  R. Hartlaub

Project ID:  2007-019

Key Research Organization(s):  British Columbia Institute of Technology

Project Location:  Kootenay

Strategic Focus Area:  Minerals


The Middle Proterozoic Belt-Purcell Basin hosts the Purcell Supergroup in southeast British Columbia. The basin is believed to represent an intracontinental rift system that has been filled by both marine and fluviatile sediments. The Sullivan Mine, one of the world's largest SEDEX Pb-Zn deposits, is hosted in the Aldridge Formation of the lower Purcell Supergroup. Overlying rocks of the middle and upper Purcell Supergroup have received much less attention in B.C., even though they host several important sediment-hosted copper deposits in Montana (Spar Lake [Troy], Rock Creek, and Montanore).

Project Area
The middle Purcell Supergroup includes clastic sediments of the Creston Formation and carbonates of the Kitchener Formation. It is the middle Creston Formation, termed the Revett in Montana, that hosts the known copper deposits. The upper Purcell Supergroup consists of shallow water clastic rocks of the Van Creek, Gateway, Phillips, and Roosvile Formations. A horizon of flood basalts and volcaniclastic rocks is termed the Nicol Creek Formation. The goal of this study was to better characterize the strata-bound base metal potential of the Middle and Upper Purcell Supergroup in British Columbia. This research focused on three main components:

  1. Detailed mapping of the geology, alteration patterns, and mineral occurrences of the economically important middle Creston Formation (Revett Formation in Montana).
  2. Examination of the petrology, geochemistry and economic potential of volcanic rocks of the Nicol Creek Formation.
  3. Geochemical and isotopic characterization of mafic dykes and felsic plutonic rocks in order to constrain their relationships with alteration zones and strata-bound mineralization.
Large cratonic basins filled with immature siliciclastic sediments are excellent source regions for sediment-hosted copper deposits. The Mesoproterozoic Belt-Purcell basin has sedimentary rock thickness of at least 19 km within the central part of the basin in BC and up to 18 km in the U.S. (Winston and Link, 1993). This large thickness of sediment was deposited in a relatively rapid period, leading to the formation of numerous sediment-hosted stratabound Cu-Ag occurrences in the quartzite-dominated Revett Formation. These deposits, including Troy, Rock Creek and Montanore, are all located in western Montana; however, evidence for sediment-hosted copper mineralization has recently been identified in southeastern British Columbia.

Several sediment-hosted copper occurrences from the Cranbrook area were examined in detail as part of this project. U-Pb geochronology samples were collected in order to better constrain the age of these mineral occurrences. An important factor limiting exploration and development in the area is the limited bedrock exposure due to thick deposits of glacial drift. Fifty samples of lodgepole pine bark were collected to test biogeochemical exploration for concealed mineralization.