In Sardinia, the Posada – Asinara mylonitic mélange zone gathers eclogitic relicts with N-MORB affinity, high-grade and medium-grade continental complexes (Carmignani et al, 1992, 1994), interpreted as the southern margin of Armorica and northern margin of Gondwana, respectively. In the Asinara Island, an intermediate to high-grade granulite crust section (Oggiano and Di Pisa, 1988) attains the deepest exposed level at Punta Scorno, where a basic complex, interleaved by cm to m thick felsic layers occurs. The felsic layers were selected for U-Pb radiometric dating by ELA-ICPMS on zircons at CNR – IGG Pavia. In the granuliteamphibolite complex, each felsic layer yielded different ranges of Concordia ages, from Neoproterozoic (672 ± 12 to 588 ± 16 Ma) until a Cambrian system closure (514 ± 22 to 506 ± 15 Ma). Early Ordovician ages spans between 491 ± 13 and 474 ± 12 Ma. Late Ordovician – Early Silurian ages fall in the 461± 10 to 435 ± 12 Ma interval; Devonian and Carboniferous age values also result. This points to a longlasting, sequence of metamorphic events with episodes of partial melting, in the lower crust.

U-Pb geochronology and geochemistry of the granulite amphibolite complex in the Asinara Island (Italy) / Gaggero L; CASINI L; Oggiano G; Tiepolo M. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - (2013). [10.1180/minmag.2013.077.5.7]

U-Pb geochronology and geochemistry of the granulite amphibolite complex in the Asinara Island (Italy)

CASINI, Leonardo;OGGIANO, Giacomo;
2013

Abstract

In Sardinia, the Posada – Asinara mylonitic mélange zone gathers eclogitic relicts with N-MORB affinity, high-grade and medium-grade continental complexes (Carmignani et al, 1992, 1994), interpreted as the southern margin of Armorica and northern margin of Gondwana, respectively. In the Asinara Island, an intermediate to high-grade granulite crust section (Oggiano and Di Pisa, 1988) attains the deepest exposed level at Punta Scorno, where a basic complex, interleaved by cm to m thick felsic layers occurs. The felsic layers were selected for U-Pb radiometric dating by ELA-ICPMS on zircons at CNR – IGG Pavia. In the granuliteamphibolite complex, each felsic layer yielded different ranges of Concordia ages, from Neoproterozoic (672 ± 12 to 588 ± 16 Ma) until a Cambrian system closure (514 ± 22 to 506 ± 15 Ma). Early Ordovician ages spans between 491 ± 13 and 474 ± 12 Ma. Late Ordovician – Early Silurian ages fall in the 461± 10 to 435 ± 12 Ma interval; Devonian and Carboniferous age values also result. This points to a longlasting, sequence of metamorphic events with episodes of partial melting, in the lower crust.
U-Pb geochronology and geochemistry of the granulite amphibolite complex in the Asinara Island (Italy) / Gaggero L; CASINI L; Oggiano G; Tiepolo M. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - (2013). [10.1180/minmag.2013.077.5.7]
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11388/134493
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