Paper No. 96-30
Presentation Time: 9:00 AM-6:30 PM
THE MOBILITY OF RARE EARTH ELEMENTS IN ALTERED SHERMAN GRANITE, LARAMIE RANGE, SOUTHEAST WYOMING
The mobility of REEs was examined in the Sherman Granite, a 1.43 Ga A-type granite located in the Laramie Range of Southeast Wyoming. Oxidized, altered granites are present in localized outcrops. Outcrop and core samples of altered granite were compared to unaltered granite for location and distribution of REEs. Optical microscopy was used to examine the extent of alteration of the granite and the distribution of zircon and allanite, both of which are accessory minerals known to contain REEs in other systems. SEM-EDS was used to qualitatively determine the REE content of minerals in both unaltered and altered samples. Optical microscopy suggests hydrothermal alteration of K-feldspars to clays, plagioclase to epidote, and biotite to fine-grained micas. All REEs in unaltered granite are associated with allanite, whereas REEs within altered granites are associated with clay minerals after K-feldspar. REEs which are spatially dispersed in unaltered granite are consolidated in clay-rich domains of hydrothermally altered granite, which suggests that REEs were mobilized during hydrothermal alteration. REEs are in high demand for technological advances, thus understanding characteristics of their mobility can help determine the feasibility of extracting REEs from source rocks.