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Journal of Undergraduate Research

Keywords

thermodynamic modeling, prediction fractional crystallization paths, andesite, trachydacite

College

Physical and Mathematical Sciences

Department

Geological Sciences

Abstract

The Isom formation is a package of distinctive ignimbrites found in an Oligocene caldera complex along the Utah-Nevada border (Best and Christiansen, 1991). Similar high-alkali rocks are also found in other caldera complexes and imply their generation is a fundamental part of the evolution of large volcanic systems (Dorais, Whitney, and Stormer, 1991). Best and Christiansen (1989) hypothesized that the Isom magma is a result of fractional crystallization of an andesite. In contrast, other large volume ignimbrites appear to involve significant mixing and hybridization, but compositional analyses of the rocks found in this caldera complex do not match these trends.

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