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. © 2009 International Association for Gondwana Research.
Multiple early Paleozoic volcanic events at the northern Gondwana margin: U-Pb age evidence from the Southern Variscan branch (Sardinia, Italy) / G. Oggiano, L. Gaggero, A. Funedda, L. Buzzi, M. Tiepolo. - In: GONDWANA RESEARCH. - ISSN 1342-937X. - 17:1(2010), pp. 44-58.
Multiple early Paleozoic volcanic events at the northern Gondwana margin: U-Pb age evidence from the Southern Variscan branch (Sardinia, Italy)
M. TiepoloUltimo
2010
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. © 2009 International Association for Gondwana Research.Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.