Tectonic setting and provenance of clastic sediments from the Ossa-Morena Zone Neoproterozoic and Early Cambrian basins (Iberian Massif, Portugal, Alentejo)

• M.F. Pereira ^[1] ; M. Chichorro ^[1]
  1. [1] Universidade de Évora

     Universidade de Évora

     Senhora da Saúde, Portugal

     
• Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 6, 2, 2004 (Ejemplar dedicado a: IV Congreso Geológico de España), págs. 161-164
• Idioma: español
• Enlaces
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• Resumen

  • Neoproterozoic-Early Cambrian clastic rocks of the Ossa-Morena Zone (Iberian M a ssifPortugal) represent two major events of syn-tectonic sedimentary deposition associated with the northern Gondwana margin geodynamic evolution: (1) The Neoproterozoic Serie Negra succession (SN) that record the filling and closure of active margin basins during the Cadomian accretion and magmatic arc development; (2) The Early Cambrian Detritic-Carbonate complexes (DCC) regarded as the filling of pull-apart basins caused by transtension; unconformably overlain the previous deformed and metamorphosed SN and a late Neoproterozoic-Early Cambrian alkaline to calc-alkaline volcanic-sedimentary complex. The main chemical differences between the SN and DCC clastic rocks are probably related with their maturity. The chondrite- and PAAS normalized REE-patterns of both SN and DCC clastic rocks present an enrichment of the LREE relative to HREE and a characteristic negative Eu-anomaly typical of continental crust with felsic magmatic nature as dominant sediment provenance. Trace-elements discrimination diagrams (La-Th-Sc and Th-Sc-Zr/10) show that the SN and DCC clastic rocks reflect the nature of an inherited continental magmatic arc source caused by the input of Cadomian detritus, which are predominantly of felsic provenance.