Neodymium Isotopic Evidence for Early Proterozoic Units in the Watersmeet Gneiss Dome, Northern Michigan (Chapter G). Temperature-Pressure Estimates of Dynamically Recrystallized Rocks in the Early Proterozoic Mountain Shear Zone, Northeastern Wisconsin (Chapter H)

摘要

There are two studies reported in the document. The purpose of the first study is to (1) describe the principal types of gneisses in the dome, (2) present the Sm-Nd data, and (3) point out the utility of Nd isotopic work in distinguishing crustal formation ages in highly complex, metamorphosed terranes. The second study consisting of field and geochemical analysis, documents the mineralogical changes and associated temperatures and pressures attendant to deformation within the Mountain shear zone, northeastern Wisconsin. Geobarometry and geothermometry applied to rocks of similar bulk composition from within and outside the shear zone provide estimates of the temperature and pressure changes produced by the ductile deformation.