Abstract

The partitioning of elements in alkali feldspars from the Clayton Peak, Alta, and Little Cottonwood stocks of the central Wasatch Range, Utah, suggests a common magmatic origin for the three intrusive bodies. With decrease in age of intrusion, the alkali feldspars show a successive depletion of Ca, Sr, and Ba and a decrease of the K/Rb ratio. Alkali feldspar phenocrysts from the Little Cottonwood stock contain higher concentrations of Ca, Sr, and Ba and a higher K/Rb ratio than the groundmass alkali feldspars, indicating an earlier period of crystallization in the melt. The phenocrysts are zoned in Ba and have relatively low concentrations in the rims and high concentrations in the centers, suggesting that they crystallized in a melt undergoing progressive depletion of barium.

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