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Paleozoic ophiolites in the Variscan suture of Galicia (northwest Spain): Distribution, characteristics, and meaning

By
Ricardo Arenas
Ricardo Arenas
1
Departamento de Petrología y Geoquímica, Universidad Complutense, 28040 Madrid, Spain
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José R. Martínez Catalán
José R. Martínez Catalán
2
Departamento de Geología, Universidad de Salamanca, 37008 Salamanca, Spain
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Sonia Sánchez Martínez
Sonia Sánchez Martínez
3
Departamento de Petrología y Geoquímica, Universidad Complutense, 28040 Madrid, Spain
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Florentino Díaz García
Florentino Díaz García
4
Departamento de Geología, Universidad de Oviedo, 33005 Oviedo, Spain
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Jacobo Abati
Jacobo Abati
5
Departamento de Petrología y Geoquímica, Universidad Complutense, 28040 Madrid, Spain
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Javier Fernández-Suárez
Javier Fernández-Suárez
5
Departamento de Petrología y Geoquímica, Universidad Complutense, 28040 Madrid, Spain
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Pilar Andonaegui
Pilar Andonaegui
5
Departamento de Petrología y Geoquímica, Universidad Complutense, 28040 Madrid, Spain
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Juan Gómez-Barreiro
Juan Gómez-Barreiro
6
Departamento de Geología, Universidad de Salamanca, 37008 Salamanca, Spain
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Published:
January 01, 2007

Allochthonous ophiolitic units in the northwestern Iberian Massif are remnants of peri-Gondwanan Paleozoic oceans sandwiched among other exotic terranes of continental and volcanic-arc derivation. All these terranes define an intricate suture zone that marks the convergence and collision between Laurussia and Gondwana. The suture is defined by three different ophiolitic ensembles: upper ophiolitic units, lower ophiolitic units, and the Somozas mélange. The lower ophiolitic units were derived from an alternation of basalts and sediments intruded by gabbros and scarce granitoids, and they formed during the opening of a marginal basin, the Galician ocean, during Late Cambrian to Early Ordovician time. This ocean was created as a back arc by the severance of a volcanic arc that had developed at the northern margin of Gondwana and formed part of the Rheic oceanic realm. The upper ophiolitic units formed during the Early Devonian from intraoceanic subduction in the early Paleozoic lithosphere of the Rheic Ocean. These suprasubduction ophiolites were formed just before the ocean closed, preceding the collision between Gondwana and Laurussia. The Somozas mélange appears in an anomalous position at the base of the Cabo Ortegal Complex. The ophiolites involved in this tectonic mélange represent an imbricate of highly dismembered oceanic lithosphere, slivers of subducted outer edge of the Gondwanan continental margin, and Paleozoic metasediments of the northern Gondwanan platform. The ophiolites might either record the development of a different peri-Gondwanan oceanic domain, or they might be equivalent to any of the other ophiolitic ensembles, and their anomalous structural position is simply a consequence of complex thrusting.

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GSA Memoirs

4-D Framework of Continental Crust

Robert D. Hatcher, Jr.
Robert D. Hatcher, Jr.
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Marvin P. Carlson
Marvin P. Carlson
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John H. McBride
John H. McBride
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José R. Martínez Catalán
José R. Martínez Catalán
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Geological Society of America
Volume
200
ISBN print:
9780813712000
Publication date:
January 01, 2007

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