Late Cambrian magmatic arc activity in peri-Gondwana: geochemical evidence from the Basal Allochthonous Units of NW Iberia

P. Andonaegui, J. Abati, R. Díez Fernández

Abstract


The north African section of the margin of Gondwana was the site of voluminous, arc-related magmatism during the late Neoproterozoic (Avalonian–Cadomian orogen). The lower (and older) metasedimentary sequence that constitutes the Basal Units of the Allochthonous Complexes of NW Iberia was deposited in that setting. In these units, sedimentation was followed by the intrusion of tonalites and granodiorites in the late Cambrian (c. 493–489 Ma). In the late Paleozoic, the collision of Gondwana and Laurussia (Variscan orogeny) deformed and metamorphosed the whole ensemble.

New whole rock geochemical analysis performed in seven samples of metatonalites and fourteen samples of metagranodiorites are characterized by: (i) slight enrichment in incompatible elements (Rb, Ba, Th, U); (ii) negative anomalies in Nb, Ta, P, and Ti; and (iii) negative anomalies in Eu. These chemical features are in agreement with a subduction-related setting for the genesis of both types of magma, what is also supported by chemical discrimination using tectonic setting diagrams. Positive anomalies of Pb suggest a crustal component. The new geochemical data reveal that the convergent orogen that ruled the paleogeography of the Gondwana periphery during the Neoproterozoic (Cadomian orogen) remained active beyond the Neoproterozoic-Cambrian transition, up to at least late Cambrian times.


Keywords


Convergent margin; Subduction; Magmatism; Whole rock geochemistry; NW Iberian Massif

Full Text:

PDF


DOI: http://dx.doi.org/10.1344/%25x

Refbacks

  • There are currently no refbacks.




Geoscience e-Journals

 

Previous

 

Random

 

Next

 

List

 

Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike License.
Geologica Acta (ISSN-1695-6133)
Biblioteca de Geologia (UB-CSIC) | Facultat de Ciències de la Terra, Martí i Franquès s/n 08028 Barcelona | Spain
Phone: +34 93 403 19 89 | Fax: +34 93 402 14 21 | E-mail: geologica-acta@ictja.csic.es
RCUB revistesub@ub.edu Avís Legal RCUB Universitat de Barcelona