Analysis of trace element distributions distal to porphyry copper deposits

Abstract

Enrichment and depletion of trace elements occurs in host rocks distal to porphyry copper deposits as a result of hydrothermal metasomatism. Subtle geochemical distributions in weakly propylitized host rocks is sufficient to indicate proximity to a mineralized system and may be applied to porphyry copper exploration. Samples collected adjacent to four porphyry copper deposits were analyzed for a multi-element suite, then normalized to the elemental concentrations of the fresh host rocks. The probability that an element has been enriched or depleted is determined by using concentrations in the unaltered host in conjunction with a calculated standard deviation. The probabilities have distinct zoning that is related to alteration around the deposits. Contribution lateral to deposits was observed with: Ag, As, Au, Bi, Br, Ca, Cu, Hg, Mn, Mo, Pb, Sb, Se, V, and Zn. Proximal to the mineralized portion of the systems elemental removal was observed with: Ba, Br, Ca, Mg, Mn, P, Pb, Ti, V, Y, and Zn.