RT Journal Article
T1 A peri-Gondwanan arc in NW IberiaI: Isotopic and geochemical constraints on the origin of thearc—A sedimentary approach
A1 Fuenlabrada Pérez, José Manuel
A1 Arenas Martín, Ricardo
A1 Sánchez Martínez, Sonia
A1 Díaz García, Florentino
A1 Castiñeiras García, Pedro
AB The arc-derived upper terrane in the NW Iberia Variscan belt contains a 3000 m thick turbiditic formation atits structural top. Most of the sandstones are feldspathic greywackes with a framework of quartz and weaklyaltered plagioclase. Rock fragments of vitric and microgranular texture are common in polymicticconglomerates and coarse-grained greywackes, together with slates, cherts and bipyramidal volcanic quartzfragments. Although recrystallization under greenschists facies conditions (chlorite and biotite zones) and thepresence of two cleavages hinder detailed textural analysis, the sandstones appear to be typically immature,first-cycle sandstones. The metagreywackes have average major and trace element compositions similar toPAAS (Post Archean Australian Shale), which is considered to reflect the composition of the upper continentalcrust. Their trace element composition is very consistent and records deposition within a convergent tectonicsetting, probably in an intra-arc basin located in a volcanic arc built on thinned continental margin. Detritalzircon populations suggest a Middle Cambrian maximum depositional age (530–500 Ma) and a Gondwananprovenance located at the periphery of the West African Craton. Nd isotope data suggest mixing Ediacaran andPaleoproterozoic sources for the provenance of the greywackes, with TDM ranging between 720 and 1215 Mawith an average of 995 Ma (n=20)—an age range unrepresented in the detrital zircon population. The Ndmodel ages are similar to those exhibited by West Avalonia, Florida or the Carolina terrane, but younger thanthose of Cambrian and Ordovician sandstones and shales from the autochthonous realm. These data suggesta westernmost location along the Gondwanan margin for the upper terrane of NW Iberia relative to otherterranes located in the footwall of the Variscan suture, consistent with several previously proposedpaleogeographic models for the NW Iberia terranes.
PB Elsevier Science B. V., Amsterdam
SN 1342-937X
YR 2010
FD 2010
LK https://hdl.handle.net/20.500.14352/42022
UL https://hdl.handle.net/20.500.14352/42022
LA eng
DS Docta Complutense
RD 23 jul 2024