Ages of Permian volcanic rocks from the Ligurian Brianc¸onnais domain (Western Italian Alps) have been determined by laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircon. Three major volcanic units yielded zircons that were dated: calc-alkaline rhyolites (285.6 2.6 Ma), andesites (with inherited cores yielded ages c. 476 Ma and older) and voluminous rhyodacites–rhyolites (272.7 2.2 Ma). Following an amagmatic, sediment-starved time gap of c. 14 Ma, alkaline volcanic activity is recorded, at the top of the sequence, by K-alkaline rhyolites dated at 258.5 2.8 Ma. The Ligurian segment of the Southern Variscan belt records transtensional and then extensional tectonics associated with the volcanic activity. The switch from calc-alkaline to alkaline activity corresponds to the transition from a post-orogenic to an anorogenic setting in the Southern Variscides; it may represent progressive and increasing delamination of the continental lithosphere, accompanied by partial melting of the lithospheric mantle.

U-Pb zircon ages for post-Variscan volcanism in the Ligurian Alps (Northern Italy). / DALLAGIOVANNA G; L. GAGGERO; MAINO M; SENO S; TIEPOLO M. - In: JOURNAL OF THE GEOLOGICAL SOCIETY. - ISSN 0016-7649. - STAMPA. - 166(2009), pp. 1-14.

U-Pb zircon ages for post-Variscan volcanism in the Ligurian Alps (Northern Italy).

GAGGERO, LAURA;
2009

Abstract

Ages of Permian volcanic rocks from the Ligurian Brianc¸onnais domain (Western Italian Alps) have been determined by laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircon. Three major volcanic units yielded zircons that were dated: calc-alkaline rhyolites (285.6 2.6 Ma), andesites (with inherited cores yielded ages c. 476 Ma and older) and voluminous rhyodacites–rhyolites (272.7 2.2 Ma). Following an amagmatic, sediment-starved time gap of c. 14 Ma, alkaline volcanic activity is recorded, at the top of the sequence, by K-alkaline rhyolites dated at 258.5 2.8 Ma. The Ligurian segment of the Southern Variscan belt records transtensional and then extensional tectonics associated with the volcanic activity. The switch from calc-alkaline to alkaline activity corresponds to the transition from a post-orogenic to an anorogenic setting in the Southern Variscides; it may represent progressive and increasing delamination of the continental lithosphere, accompanied by partial melting of the lithospheric mantle.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11567/221789
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