2002/05/01 by Jörg Geldmacher, Valentín R. Troll, C. H. Emeleus +1 · 4 citations
Earth and Planetary Sciences · #Geological and Geochemical Analysis #High-pressure geophysics and materials #earthquake and tectonic studies
paper · doi:10.1144/sjg38010055
openalex publication_date 2002/05/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/19
Synopsis Using Pb isotope ratios we compare crustal contamination of primitive to evolved magmas from the Ardnamurchan and nearby Rum Igneous Centres, located on different crustal provinces in the British Tertiary Igneous Province (BTIP). The results confirm that compositional variations of parental cone-sheet magmas in Ardnamurchan can be explained by assimilation of granulite facies Lewisian gneiss at moderate crustal levels and subsequent contamination of evolved magmas with Moine schist metasediments within the uppermost crust during fractional crystallization. In contrast, samples from the Rum Centre have an uncontaminated mantle signature for the basaltic end-member, whereas the evolved rocks show Pb isotope evidence of contamination by Lewisian amphibolite facies rocks. Rum is separated from Ardnamurchan by a major thrust. The absence of a Moine-type isotopic influence in the Rum rocks supports an earlier interpretation, based on field evidence, that these overthrust rocks were eroded from Rum prior to the Palaeocene magmatic activity.