LEAD-ZINC-SILVER ORE DEPOSITS HOSTED BY CAMBRIAN CARBONATES IN THE SOUTHERN KOOTENAY ARC, SOUTHEAST BRITISH COLUMBIA

Peritidal to deep-water Cambrian carbonates in the southern Kootenay Arc host numerous Pb-Zn-Ag orebodies ranging from showings to deposits with extensive production histories. The ore deposits were emplaced in the Lardeau Trough succession along the west flank of the Windermere High. Occurring along the entire Kootenay Arc, they are hosted by the Lower Cambrian Badshot Formation and correlative Reeves Member, and the Middle to Upper Cambrian Metaline and Nelway formations. The orebodies define several mining camps including the Salmo, and Duncan. Tectonized orebodies containing stratiform ore resembling sedimentary-exhalative deposits (e.g. Reeves MacDonald and Jersey) predominate but Mississippi-Valley-Type orebodies (Red Rock, Pend Oreille), mantoe deposits (Bluebell), deeply oxidized ore (e.g. Lomond and Oxide) occur. Cretaceous granitic intrusion altered many occurrences to skarn-type deposits (e.g. Emerald and H. B).

The metamorphic grades are mainly lower amphibolite, increasing to kyanite and silimanite grade on Kootenay Lake. In the Salmo district, the grade decreases abruptly eastward across the Black Bluff fault. Orebodies and carbonates in the Metaline district of northern Washington State and east side of the Black Bluff fault in B. C. preserve original depositional and emplacement fabrics but most deposits in the Kootenay Arc to the west and north display isoclinal folding, and effects of regional and contact metamorphism.

Sulphides at the Bluebell are late fracture-controlled replacements emplaced as manto, vein, and pipe-shaped masses. The crystal-lined vugs and sulphide veins crossing stratigraphy and late structures at the Bluebell indicate emplacement after mid-Jurassic to earliest Cretaceous regional deformation and metamorphism. Major orebodies in the Reeves are tectonized and metamorphosed stratiform deposits in dolomite marble. They appear to record a syngenetic to early diagenetic phase of Paleozoic emplacement and subsequent epigenetic Jurassic to earliest Cretaceous phase. The MVT and oxide deposits in the Nelway and Metaline of the Salmo and Metaline districts were not subjected to the higher metamorphism and multi-phase folding that Cambrian deposits in the Reeves experienced but display features suggesting emplacement after regional deformation.