Xenoliths in the lamprophyre dykes of Lomondside: constraints on the nature of the crust beneath the southern Dalradian

Abstract

Synopsis Xenoliths within a late-Caledonian lamprophyre dyke intruded into Dalradian metasediments reveal the presence at depth of Dalradian rocks of relatively high regional metamorphic grade and probable Highland Border Complex rocks. The xenolith suite is largely composed of fragments of cognate cumulate rocks together with metamorphosed country rocks both associated with a deep magma chamber. The latter formed close to the Highland Boundary Fault, which dips to the north beneath a thickened Dalradian pile. Pyrope-rich garnets within the xcnocryst assemblage may indicate that the lamprophyre magma originated in high pressure rocks within the mantle.