Field techniques for the rapid extraction and estimation of copper, lead, and zinc from altered rock are described, together with their application in the Tintic district, Utah. Either sulfuric acid or an acetic acid-ammonium acetate reagent is feasible as an extractant; but of these two, sulfuric acid is preferred.Data obtained by partial extraction methods show that zinc and lead are concentrated in altered extrusive rocks 350 to 500 feet above a horizontal, pipelike ore body in limestone, where the extrusive rocks are cut by a fracture zone related to a strong premineral cross fault. Such concentrations are absent in altered but unbrecciated igneous rocks above the continuation of the same ore body in an unfaulted area. In many places premineral alteration diminished the original heavy metal content of the igneous rocks, and in unfractured extrusive rocks the hydrothermally leached rock yields a negative anomaly even though the rock lies only a short distance above ore.

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