GEOMETRY AND CONSTRUCTION HISTORY OF AN ASYMMETRIC LACCOLITHIC INTRUSIVE CENTER: MOUNT HILLERS, HENRY MOUNTAINS, UTAH
The new data presented here are concentrated on the northern side of Mount Hillers. However, our analysis incorporates the previously well-studied southern portion of the mountain to provide a comprehensive geometric configuration of the intrusive center. After establishing an accurate geometry of the entire intrusive center in the field, various laboratory datasets allow us to better understand how the asymmetric relationship between the main igneous body and host rock progressively developed. Cross-cutting relationships between igneous bodies with clear variations in igneous texture allow us to identify the timing of different component intrusions. Anisotropy of magnetic susceptibility data allow us to constrain paleo-magma flow patterns preserved as fabrics in the plagioclase hornblende porphyry igneous rocks. Geochemical data and thin section analysis allow us to distinguish between different magma families by evaluating mineralogical and textural variations among igneous samples.
Multiple cross sections illustrate the detailed architecture of the Mount Hillers intrusive center mapped at a 1:10,000 scale. A detailed study of this intrusive center reveals crucial stages of magma emplacement and host rock deformation that were not recognized during previous mapping.