Microstructures and crystal fabrics of the Moine Thrust zone and Moine Nappe: history of research and changing tectonic interpretations

Abstract

AbstractIn this paper we review microstructural and petrofabric work carried out on the Moine Thrust zone and overlying thrust nappes. Our review is primarily historical, and starts with contributions made by both ‘amateur’ and ‘professional’ geologists from the 1880s through to the early 1920s during, and immediately following, the original field-mapping of the Moine Thrust zone by the Geological Survey. From the 1920s to the early 1950s contributions were first dominated by Geological Survey work on the microstructural and metamorphic transition between the thrust zone mylonites and the overlying Moine metasedimentary rocks. Subsequent university-based quartz petrofabric work, primarily focused on the Moines, would ultimately lead to the ‘Moine Petrofabric Controversy’ that ran from the late 1940s to the early 1960s. The later stages of this controversy overlapped, from the early 1950s–mid 1960s, with a phase of microstructural and quartz petrofabric work that concentrated on the thrust zone mylonites and immediately overlying Moine Schists. Our review concludes with an overview of microstructural, petrofabric and related strain analyses undertaken since the early 1970s, both within the Moine Thrust zone and its immediate foreland and in the overlying higher grade thrust sheets. Throughout our review we emphasize and track the changing tectonic interpretations that have been placed on available microstructural and petrofabric data.