Abstract

The so called “pinto” effect of Chinle strata in Arizona and Utah is believed to be: (1) caused by local lateral movement of solutions, (2) unrelated to a simple lateritic profile, (3) dependent on a sequence of geologic events rather than geometry of position, (4) related to argillic alteration in the ore zone, (5) an effect possibly formed after doming, and (6) caused by heated solutions associated with ore deposition rather than lateritic weathering. The occurrence of the “pinto” both above and below the ore-bearing strata, the association with chertification, dolomitization and argillic alteration, and the absence of lateritic mineralization are major factors which preclude a lateritic origin.

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