Abstract

Peculiar dark pseudomorphs after orthoclase phenocrysts occur along fracture zones near the margin of the metallized area at Ray, Arizona. The most intensely altered crystals contain no recognizable orthoclase but consist principally of chlorite and calcite plus small, but variable amounts of sericite, and quartz. Rutile, leucoxene, kaolinite, allophane, hydromica, and sulfides are present in some thin sections.It is thought that the pseudomorphs were formed by solutions loaded with calcium, magnesium, and iron that moved upward and outward from the ore body where the rocks had been intensely sericitized and the bases other than potassium removed to a considerable degree.The occurrence emphasizes the problem of the time of alteration. The propylitic stage is often considered to be an early state whereas it probably is often a marginal stage that coincides in time with sericitization, or other alteration, near the center of activity. An expanding sericite-quartz stage of alteration may cause those minerals to invade the propylitic rock and thus furnish evidence of an age difference, but in fact propylitization is probably taking place farther out at the same time.

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