SILURIAN AND EARLY DEVONIAN SINISTRAL DEFORMATION OF THE RATAGAIN GRANITE, SCOTLAND - CONSTRAINTS ON THE AGE OF CALEDONIAN MOVEMENTS ON THE GREAT GLEN FAULT SYSTEM

The Ratagain granite complex (425 +/- 3 Ma) was emplaced adjacent to the Strathconan Fault, an important member of the Great Glen fault system, and was deformed by sinistral shear associated with this fault just prior to its complete crystallization. It was deformed again by low temperature sinistral mylonite and breccia zones penecontemporaneously with the regional minette dyke swarm (410-395 Ma). Very little evidence is seen in the complex of deformation in the high temperature/post-crystallization interval, and it is concluded that Caledonian sinistral motion on the Strathconan Fault occurred in two distinct phases: Mid-Silurian (Wenlock) and Early Devonian.