This project will use the petrologic framework of voluminous, middle Tertiary, intermediate to silicic volcanism in east- central Nevada as a basis for : (1) A study of the petrologic processes acting at an instant in the evolution of the system, by completing work on zonation in the Kalamazoo Tuff; (2) A detailed analysis of isotopic and textural changes during inception, climax, and waning of the system; and (3) Development of a mass and thermal budget of an evolving magma system. The rocks of east-central Nevada are particularly suited for this study because they represent a large volume (thousands of cubic kilometers) of metaluminous magma, the intrusive equivalent of which could be a typical "calcalkaline" batholith. Also, they have been characterized with respect to their age, texture, mineralogy, and major-element, trace-element, and isotopic compositions, all of which are consistent with a three stage evolution of the magmatic system.
