Stillwater Complex, Montana— Structure, mineralogy, and petrology of the basal zone with emphasis on the occurrence of sulfides

Abstract

The Basal zone of the Stillwater Complex is divided into two members, a Basal norite and an overlying Basal bronzite cumulate. The Basal norite is composed of alternating lensoid masses or layers of rock and is extremely variable both laterally and vertically in mineralogy, texture, grain size, and crystallization sequences, and the Basal bronzite cumulate is composed of layers of fine-to coarse-grained granular orthopyroxene cumulates and exhibits relatively regular properties laterally.