GEOCHEMISTRY AND U-PB ZIRCON AGE OF THE INTERNAL OSSA-MORENA ZONE OPHIOLITE SEQUENCES: A REMNANT OF RHEIC OCEAN IN SW IBERIA

Authors

  • Jorge Pedro Departamento de Geociências, Universidade de Évora and Centro de Geologia, Universidade de Lisboa, Portugal
  • Alexandre Araújo Departamento de Geociências and Centro de Geofísica, Universidade de Évora, Portugal
  • Paulo Fonseca Departamento de Geologia and Centro de Geologia, Universidade de Lisboa, Portugal
  • Colombo Tassinari Centro de Pesquisas Geocronológicas, Instituto de Geociências, Universidade de São Paulo, Brasil
  • António Ribeiro Centro de Geologia, Universidade de Lisboa, Portugal

DOI:

https://doi.org/10.4454/ofioliti.v35i2.390

Keywords:

Abstract

The Early Paleozoic geodynamic evolution in SW Iberia is believed to have been dominated by the opening of the Rheic Ocean. The Rheic Ocean is generally accepted to have resulted from the drift of peri-Gondwanan terranes such as Avalonia from the northern margin of Gondwana during Late Cambrian- Early Ordovician times. The closure of the Rheic Ocean was the final result of a continent-continent collision between Gondwana and Laurussia that produced the Variscan orogen. The Ossa-Morena Zone is a peri-Gondwana terrane, which preserves spread fragments of ophiolites - the Internal Ossa-Morena Zones Ophiolite Sequences (IOMZOS). The final patchwork of the IOMZOS shows a complete oceanic lithospheric sequence with geochemical characteristics similar to the ocean-floor basalts, without any orogenic fingerprint and/or crustal contamination. The IOMZOS were obducted and imbricated with high pressure lithologies. Based on structural, petrological and whole-rock geochemical data, the authors argue that the IOMZOS represent fragments of the oceanic lithosphere from the Rheic Ocean. Zircon SHRIMP U-Pb geochronological data on metagabbros point to an age of ca. 480 Ma for IOMZOS, providing evidence of a well-developed ocean in SW Iberia during this period, reinforcing the interpretation of the Rheic Ocean as a wide ocean among the peri-Gondwanan terranes during Early Ordovician times.

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Published

2010-03-01

How to Cite

Pedro, J., Araújo, A., Fonseca, P., Tassinari, C., & Ribeiro, A. (2010). GEOCHEMISTRY AND U-PB ZIRCON AGE OF THE INTERNAL OSSA-MORENA ZONE OPHIOLITE SEQUENCES: A REMNANT OF RHEIC OCEAN IN SW IBERIA. Ofioliti, 35(2), 117-130. https://doi.org/10.4454/ofioliti.v35i2.390

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