Abstract

The chief pegmatite, near Texas Creek, Fremont County, Colorado, is the sole Li pegmatite in a large dike swarm. The cleavelanditic bodies, one of which carries lepidolite, are fracture-controlled replacement units localized in the thick lower “tail” of the dike which strikes at right angles to the rest of the pegmatite. The accessory mineral assemblage (apatite, beryl, Bi-carbonate, columbite, lepidolite, rose muscovite, spessartite, topaz, colored tourmalines, zinnwaldite) shows striking and close similarities to those of the Brown Derby pegmatite of Colorado and the Harding and Pidlite pegmatites in New Mexico. The Brown Derby and Harding dikes are of the same age, and it is suggested that the C hief and Pidlite pegmatites also are part of the same petrologic province on the basis of their accessory mineral and elemental assemblages.

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