Rheic Ocean ophiolitic remnants in southern Iberia questioned by SHRIMP U-Pb zircon ages on the Beja-Acebuches amphibolites
Date
2008
Authors
Azor, A
Rubatto, Daniela
Simancas, J F
Gonzalez-Lodeiro, F
Martınez Poyatos, D
Martin Parra, L.M.
Matas, J.
Journal Title
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Volume Title
Publisher
American Geophysical Union
Abstract
The Rheic Ocean was a major oceanic domain between Avalonia and Gondwana in Ordovician-Silurian times. Most of the Paleozoic plate reconstructions assume that the Rheic Ocean suture lies within southern Iberia, coinciding with the contact between the South Portuguese Zone and the Ossa-Morena Zone. This paper reports four Sensitive High Resolution Ion Micro-Probe (SHRIMP) U-Pb zircon ages from mid-ocean ridge basalt (MORB)-featured rocks of the Beja-Acebuches Amphibolite unit, which crops out along the boundary between the Ossa-Morena and the South Portuguese Zone, and is considered its most conspicuous suture unit. The obtained ages range from 332 ± 3 to 340 ± 4 Ma, corresponding to the crystallization of the mafic protoliths. These Early Carboniferous ages for the Beja-Acebuches aniphibolites imply that this unit can no longer be viewed as an ophiolite belonging to the Rheic Ocean suture, since this oceanic domain was presumably closed in Devonian times. Tectonic reconstructions joining in a single suture line the Beja-Acebuches Amphibolite unit in southern Iberia to either the Devonian Lizard ophiolite in southern England or the root zone of the Devonian/Ordovician ophiolitic units in northwest Iberia must be therefore reconsidered because of the age difference. We interpret the Beja-Acebuches Amphibolite unit to represent a narrow and very ephemeral realm of oceanic-like crust that opened in Early Carboniferous times, after total consumption of the Rheic Ocean. We suggest that a mantle plume underneath southern Iberia in Early Carboniferous times is the most plausible large-scale geodynamic scenario for the formation of these MORB-featured rocks.
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Keywords
Keywords: amphibolite; Avalonia; geodynamics; Gondwana; mantle plume; mid-ocean ridge basalt; oceanic crust; ophiolite; Ordovician; protolith; SHRIMP dating; Silurian; suture zone; tectonic reconstruction; uranium-lead dating; England; Eurasia; Europe; Iberian Peni
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Source
Tectonics
Type
Journal article
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DOI
10.1029/2008TC002306
Restricted until
2037-12-31