Advertisement

Contributions to Mineralogy and Petrology

, Volume 131, Issue 2–3, pp 196–209 | Cite as

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

  • Jörg Geldmacher
  • Karsten M. Haase
  • Colin W. Devey
  • C. Dieter Garbe-Schönberg
Article

Abstract

Abundant cone sheets form one of the last magmatic stages in the Tertiary central complex on the Scottish peninsula of Ardnamurchan and can be grouped into a younger inner and an older outer suite relative to a gabbro intrusion. Most of the cone-sheets consist of tholeiitic to transitional basalt with MgO contents between 7.5% and 4%, although more evolved rocks also occur (to 0.5% MgO). The mafic samples are slightly enriched in the light rare earth elements (Chondrite-normalized La/Sm ∼1.1), the enrichment increases in the more evolved rocks. The compositional variation of the basaltic rocks is mainly due to crystal fractionation of olivine and clinopyroxene at depths of ∼10 km but trace elements show simultaneous assimilation of Archean 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 implies that the melts ascended successively but within a short period of time. The parental magmas of the Ardnamurchan cone-sheets must have formed at relatively shallow depths in the mantle and are comparable to the youngest tholeiitic lavas from the neighbouring island of Mull.

Keywords

Olivine Basaltic Magma Parental Magma Crustal Contamination Crystal Fractionation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • Jörg Geldmacher
    • 1
  • Karsten M. Haase
    • 2
  • Colin W. Devey
    • 1
  • C. Dieter Garbe-Schönberg
    • 1
  1. 1.Geologisch-Paläontologisches Institut der Universität Kiel, Olshausenstr. 40, D-24118 Kiel, GermanyDE
  2. 2.Max-Planck-Institut für Chemie, Postfach 3060, D-55020 Mainz, GermanyDE

Personalised recommendations