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Multiple early Paleozoic volcanic events at the northern Gondwana margin: U–Pb age evidence from the Southern Variscan branch (Sardinia, Italy)

Oggiano, Giacomo and Gaggero, Laura and Funedda, Antonio and Buzzi, Laura and Tiepolo, Massimo (2010) Multiple early Paleozoic volcanic events at the northern Gondwana margin: U–Pb age evidence from the Southern Variscan branch (Sardinia, Italy). Gondwana Research, Vol. 17 (1), p. 44-58. ISSN 1342-937X. Article.

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DOI: 10.1016/j.gr.2009.06.001

Abstract

In Sardinia, one of the southernmost remains of the European Variscan belt, a crustal section through different Gondwanan paleodomains is largely preserved. Laser ablation ICP-MS U–Pb ages on undoubtedly igneous sites of the zircons were determined on the Lower Palaeozoic volcanic rocks, constrained by defined field relationships, thus evidencing three subsequent volcanic events:
I. Intermediate and felsic (491.7 ± 3.5 Ma ÷ 479.9 ± 2.1 Concordia ages) transitional volcanic rocks embedded within a Cambro–Ordovician terrigenous succession, that occurs with continuity in external and inner nappes, bounded to the top by the Sardic unconformity.
II. This Cambrian–Lower Ordovician succession is cut by calc-alkalic rhyodacites, which yielded a Concordia age of 465.4 ± 1.4 Ma, confirming their pertinence to the huge, bimodal Mid-Ordovician arc volcanism, commonly interpreted as the widespread marker of the Rheic ocean subduction.
III. Alkalic metaepiclastites in the external nappe, within the post-Caradocian transgressive sequence, dated at 440 ± 1.7 Ma, likely related to rifting and collapse of the Mid-Ordovician volcanic arc.
In the reshaped Lower Palaeozoic stratigraphy of Sardinia, the timing of the early steps of the Variscan Wilson cycle can be inferred.

Item Type:Article
ID Code:3380
Status:Published
Refereed:Yes
Uncontrolled Keywords:Cambrian ordovician, sardic phase; volcanism, U–Pb zircon geochronology, north Gondwana margin, Sardinia
Subjects:Area 04 - Scienze della terra > GEO/03 Geologia strutturale
Divisions:001 Università di Sassari > 01 Dipartimenti > Scienze botaniche, ecologiche e geologiche
Publisher:Elsevier
ISSN:1342-937X
Copyright Holders:© 2009 International Association for Gondwana Research
Deposited On:13 Jan 2010 12:01

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