Geochemical evolution of high-pressure mafic granulites from the Bacariza formation (Cabo Ortegal complex, NW Spain): An example of a heterogeneous lower crust

G. Galán, A. Marcos

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11 Citations (Scopus)

Abstract

The Cabo Ortegal complex (northwestern Iberian massif) is a klippen formed of several structural units stacked during the Hercynian collision. All these units include ultramafic rocks, metabasites and quartz-feldspathic gneisses affected by different metamorphic conditions. The Bacariza formation is heterogeneous showing a conspicuous layering mainly defined by alternate high-pressure ultrabasic-to-basic granulites, retrogressed garnet amphibolites of intermediate composition and rare acid rocks forming garnet trondhjemitic gneisses. This layering is inherited from a gabbroic protolith showing a composition rich in Fe and Ti. Major and trace elements of these rocks can be correlated to continental tholeiitic series of extensional settings. These high-pressure granulites are situated in normal contact between ± serpentinised ultramafic rocks and other high-grade metabasites with less-evolved and more-depleted composition comparable to T-type and N-type MORB. It is suggested that the layered gabbro-type protolith was part of a continuous mafic crust. This crust was initially formed during Early Ordovician in a continental extensional setting and progressively evolved to oceanic spreading. © Springer-Verlag 1997.
Original languageEnglish
Pages (from-to)539-555
JournalInternational Journal of Earth Sciences
Volume86
Issue number3
Publication statusPublished - 1 Jan 1997

Keywords

  • Amphibolites
  • Eclogites
  • Geochemistry
  • Gneisses
  • Hercynian belt
  • Mafic granulites

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