Abstract

Trace element content of more than 1,500 bedrock samples from the vicinity of the Valley Copper, Bethlehem-JA, Lornex, and Highmont porphyry copper deposits in the Highland Valley of British Columbia has been investigated. Chemical variations in fresh rocks of the Guichon Creek batholith are consistent with a model of fractional crystallization of a calc-alkaline dioritic magma. Cu, together with the trace elements Co, Mn, Ni, V, and Zn, is depleted with increasing fractionation, and relatively low concentrations are characteristic of the more felsic core of the batholith. Geochemical patterns near the deposits are described in relation to primary lithology, hydrothermal alteration, and mineralization. Cu and S show the greatest geochemical contrast with halos extending at least 0.5 km from the principal mineralized zones. B anomalies, in part associated with breccia pipes, also extend beyond the alteration envelopes. Dispersion of the lithophile elements Rb, Sr, and Ba, and to a lesser degree Zn and Mn, is influenced by type and intensity of wall-rock alterations. As a result their halos of enrichment and/or depletion do not extend beyond the alteration envelopes. It is concluded that Cu and S provide the most extensive and useful exploration target.

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