Abstract

Machine-plotted maps of metal distributions, combined with field work, indicate the presence of a previously unrecognized regional zoning pattern in the Taseko Lakes and Pemberton map-areas. Mineral deposits occur in well-defined camps, the most productive of which has been the Bridge River gold camp. A distinctive asymmetric metal and mineral zoning pattern occurs in the Bridge River district. Two elongate, northwesterly trending centers of gold-bearing vein deposits lie within a larger area characterized by antimony minerals. The antimony zone is succeeded to the northeast by a mercury zone. This pattern is explained by mineral deposition under a regional thermal gradient decreasing outward from the eastern margin of the Coast Plutonic Complex, implying that mineralization occurred during or shortly after final cooling of the eastern margin of the Coast Plutonic Complex about 50 m.y. ago.Porphyry deposits occur in geographically separate areas from most vein deposits. Porphyry mineralization occurred during the Late Cretaceous, early Tertiary, and Miocene. Copper-molybdenum-gold porphyry deposits characterize the first two events, whereas porphyry molybdenum deposits formed during the Miocene. Principal movements along the Yalakom fault predated mineral deposition in the Bridge River camp. Late Tertiary porphyry molybdenum deposits appear genetically related to Cascade volcanism rather than to plutonism of the Coast Plutonic Complex.

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