The petrogenesis of Tertiary cone-sheets in Ardnamurchan, NW Scotland; petrological and geochemical constraints on crustal contamination and partial melting

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doi: 10.1007/s004100050388
Authors:Geldmacher, Jörg; Haase, Karsten M.; Devey, Colin W.; Garbe-Schönberg, C. Dieter
Author Affiliations:Primary:
Universität Kiel, Geologisch-Paläontologisches Institut, Kiel, Federal Republic of Germany
Other:
Max-Planck-Institut für Chemie, Federal Republic of Germany
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 131(2-3), p.196-209. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1998
Note:In English. 70 refs.; illus., incl. 4 tables, sketch map
Summary:Abundant cone sheets form one of the last magmatic stages in this Tertiary central complex and can be grouped into a younger inner and an older outer suite relative to a gabbro intrusion. Most of the cone sheets are tholeiitic to transitional basalt with MgO 7.5-4%, though some more evolved rocks (MgO to 0.5%) also occur. The mafic samples are slightly enriched in the LREE (chondrite-normalized La/Sm ∼ 1.1), the enrichment increasing in the more evolved rocks. Compositional variation in the basaltic rocks is mainly due to crystal fractionation of olivine and clinopyroxene at depths of ∼ 10 km, but trace elements indicate simultaneous assimilation of Lewisian granulite crust. The andesitic to rhyolitic lavas formed by fractional crystallization from the contaminated basaltic magma coupled with assimilation of Proterozoic Moine metasediments at uppermost crustal levels. The occurrence of composite cone sheets with basaltic and rhyolitic parts and mixtures between these magmas is taken to imply that the melts ascended successively but within a short period of time. It is considered that the parental magmas of the Ardnamurchan cone sheets must have been formed at relatively shallow depths in the mantle and are comparable to the youngest tholeiitic lavas from the neighbouring island of Mull. [R.A.H.]
Sections:Petrology
Subsections:Igneous petrology
Subjects:Archean; Basalts; Cenozoic; Crust; Crystal fractionation; Fractional crystallization; Gabbros; Genesis; Geochemistry; Igneous rocks; Intrusions; Isotope ratios; Lava; Magma contamination; Magmas; Melting; Metamorphic rocks; Metasedimentary rocks; Plutonic rocks; Precambrian; Tertiary; Volcanic rocks; Ardnamurchan; Argyllshire Scotland; Europe; Great Britain; Highland region Scotland; Scotland; United Kingdom; Western Europe; Northwestern Scotland
Coordinates:N564000 N565000 W0054000 W0062000
Abstract Numbers:98M/4279
Record ID:1999057556
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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