Rb–Sr and U–Pb isotopic data for granulite facies rocks, forming textural relics with respect to eclogite facies metamorphism in the Western Gneiss Region (WGR) of Norway, highlight the importance of textures and mineral reaction kinetics for the interpretation of geochronological data. Studied rocks from Bårdsholmen, southern WGR, were subjected to granulite facies metamorphism at 955 ± 3 Ma (...

Garnet-whole rock and garnet-mineral isochrons were determined on granulite facies gneisses and amphibolites from the Archean Pikwitonei Granulite Domain of the Superior Province, and the Proterozoic Central Gneiss Belt and Adirondack Highlands of the Grenville orogen. The Sm-Nd ages obtained from Archean garnets 0.1-0.5 cm in length are 30-110 Ma younger than the U-Pb ages obtained on the same...

Metamorphic core complexes in the western North American Cordillera are commonly interpreted as result of a single phase large-magnitude extension during middle to late Cenozoic. We present evidence that mylonitic shear zones Harcuvar and Buckskin-Rawhide west-central Arizona also accommodated an earlier Late Cretaceous early Paleocene. Microstructural data indicate substantial top-NE mylonitiz...