Temperature-time evolution of the Assynt Terrane of the Lewisian Gneiss Complex of Northwest Scotland from zircon U-Pb dating and Ti thermometry

摘要

The Lewisian Gneiss Complex of Northwest Scotland is a classic Precambrian basement gneiss complex. The Lewisian is divided into a number of terranes on the basis of structural, metamorphic and geochronological evidence. The most well-studied of these is the Assynt Terrane, which forms the central part of the Lewisian outcrop on the Scottish mainland. Field evidence shows that it has a complex tectonothermal history, the early stages of which remain poorly constrained. This paper sets out to better understand the chronology and thermal evolution of the Assynt Terrane through zircon U-Pb dating and Ti-in-zircon thermometry, the latter applied to the Lewisian for the first time. This is placed in context by integration with detailed field mapping, sample petrography, zircon cathodoluminescence (CL) imaging and rare earth element (REE) analysis.