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VII
Migmatization, eclogitization
and magmatism
7.1. Introduction
7.2. Leucosomes
7.3. Eclogites
7.4. Orthogneisses
7.5. Discussion
7.6. General discussion
7.1. Introduction
This chapter deals with the rocks with
igneous protoliths from the Banded Gneiss and
the Eclogite Band formations (HP–HT Upper
Allochthon) of the Cabo Ortegal Complex (NW
Iberia). These results will be published in several
articles after defending the present PhD thesis.
When the provenance of theUpper Allochthon
was investigated through the analysis of detrital
zircon from the metasedimentary rocks of the
Banded Gneiss (HP–HT; chapter 6) and Cariño
Gneiss (IP; chapter 5) formations, it was made
evident that a magmatic arc was active at the
margin of the Gondwana supercontinent in
the Neoproterozoic–Cambrian, from at least
c.
780 to
c.
490 Ma. Furthermore, as the HP–HT
metasedimentary rocks (Banded Gneisses) have
a Gondwanan provenance, it was concluded
that the metamorphic event that gave the HP–
HT characteristics to the bottom member of the
Upper Allochthon was driven by a subduction
event, where the margin of Gondwana subducted
under the northern continent, most probably
Laurrusia.
This chapter aims to assess the conditions of
the magmatic arc´s igneous activity, the HP–
HT metamorphic event and the generalised