Physical Sciences and Mathematics Commons^™

U/Pb Sphene Date Of Mylonitization Associated With The Proterozoic Laramie Peak Shear Zone, Laramie Mountains, Wy, Phillip Resor, K Chamberlain, A Snoke, C Frost

Phillip G Resor

In this paper, we show that deformation can be dated by combining mesoscopic and microscopic structural observations with an understanding of metamorphic mineral reactions and U-Pb ages of newly grown sphene (titanite). This approach can be used on a variety of rock types that have been deformed at a wide range of metamorphic conditions. In an example from the Proterozoic Laramie Peak shear zone of southeastern Wyoming, a single period of syntectonic sphene growth in sheared mafic dikes is documented both by a strong spatial relationship between deformation and metamorphism and by sphene microtextures. U-Pb analyses of sphene separates give …