Pb-isotope evidence for contrasting crustal contamination of primitive to evolved magmas from Ardnamurchan and Rum; implications for the structure of the underlying crust

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doi: 10.1144/sjg38010055
Authors:Geldmacher, J.; Troll, V. R.; Emeleus, C. H.; Donaldson, C. H.
Author Affiliations:Primary:
San Diego State University, Department of Geological Sciences, San Diego, CA, United States
Volume Title:Scottish Journal of Geology
Source:Scottish Journal of Geology, Vol.38(Part 1), p.55-61. Publisher: Scottish Academic Press, Edinburgh, United Kingdom. ISSN: 0036-9276
Publication Date:2002
Note:In English. 38 refs.; illus., incl. 1 table, geol. sketch map
Summary: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 Paleocene magmatic activity.
Subsections:Igneous petrology
Subjects:Amphibolite facies; Assimilation; Cenozoic; Crust; Facies; Fractional crystallization; Geochemistry; Gneisses; Granulite facies; Isotope ratios; Isotopes; Large igneous provinces; Lead; Magma contamination; Magmas; Magmatism; Metals; Metamorphic rocks; Pb-206/Pb-204; Pb-207/Pb-204; Pb-208/Pb-204; Radioactive isotopes; Stable isotopes; Tertiary; Ardnamurchan; Argyllshire Scotland; Europe; Great Britain; Hebrides; Highland region Scotland; Inner Hebrides; Inverness-shire Scotland; Rhum; Scotland; United Kingdom; Western Europe
Coordinates:N565500 N574500 W0060000 W0063000
Abstract Numbers:03M/2071
Record ID:2003036852
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
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