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Sr, Nd isotope evidence for an enriched mantle component in the origins of the Hercynian gabbro-granite series of the \"Serie dei Laghi\" (Southern Alps, NW Italy). (Articolo in rivista)

Type

Articolo in rivista (Classe)
Prodotto della ricerca (Classe)

Label

Sr, Nd isotope evidence for an enriched mantle component in the origins of the Hercynian gabbro-granite series of the \"Serie dei Laghi\" (Southern Alps, NW Italy). (Articolo in rivista) (literal)

Anno

2002-01-01T00:00:00+01:00 (literal)

Alternative label

Pinarelli L., Del Moro A., Boriani A., Caironi V. (2002)
Sr, Nd isotope evidence for an enriched mantle component in the origins of the Hercynian gabbro-granite series of the "Serie dei Laghi" (Southern Alps, NW Italy).
in European journal of mineralogy (Print)
(literal)

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Pinarelli L., Del Moro A., Boriani A., Caironi V. (literal)

Pagina inizio

403 (literal)

Pagina fine

415 (literal)

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This paper gives a picture about the genesis and the ultimate nature of the primitive magmas of a Permian gabbro-granite sequence of \"Serie dei Laghi\" (Southern Alps). As a result, it contributes to the more general question of the nature of the post-collision Hercynian mantle beneath the Southalpine domain. Through the discussion of new isotopic (Sr, Nd) and geochemical (major, trace elements, Rare Earth elements) data, along with previous geological, petrographic, and geochemical results, it was inferred an enriched mantle component, which produced crustal chemical and isotopic characters even in the mafic rocks of the series. (literal)

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14 (literal)

Rivista

European journal of mineralogy (Rivista)

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Volume uscito nel 2003 (literal)

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12 (literal)

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The identification of primary magma compositions in plutonic series from orogenic settings is a crucial problem, since even the mafic rocks exhibit crustal chemical and isotopic characters. In the \"Serie dei Laghi\", large Permian granitoids associated with mafic-intermediate stocks and dykes (Appinite suite) are exposed. The rocks were emplaced in a post-collision environment, in which lithosphere extension triggered upwelling of hot astenosphere, thermal perturbation and magma generation. Extensive crustal contamination of basaltic magmas rising from the mantle resulted in calc-alkaline affinity and orogenic-like geochemical signatures. The presence of such crustal characters even in the mafic rocks, in the past has been interpreted as an evidence of extensive crustal interaction which obliterated the original mantle characteristics. The results of the present study suggest instead that the Permian gabbro-noritic Appinites are mantle derivatives that underwent very little, if any, crustal contamination. Their overall geochemical and isotope characteristics indicate an enriched mantle source. Furthermore, on the basis of the integrated geochemical-isotope study presented, it may be concluded that the entire Serie dei Laghi magmatic series was generated through complex crust-mantle interaction mechanisms, starting from a mantle-derived magma isotopically similar to gabbro-noritic Appinites. (literal)

Note

ISI Web of Science (WOS) (literal)

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Laura PINARELLI (1), Aldo DEL MORO(2), Attilio BORIANI(3) and Valeria CAIRONI(3) (1) CNR- IGG Sezione di Firenze, Via La Pira 4, 50121 Firenze, Italy (2) CNR- IGG Sede, Via Moruzzi, 1, 56124 Pisa, Italy (3) Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Botticelli 23, 20133 Milano, Italy (literal)

Titolo

Sr, Nd isotope evidence for an enriched mantle component in the origins of the Hercynian gabbro-granite series of the \"Serie dei Laghi\" (Southern Alps, NW Italy). (literal)

Abstract

In the Serie dei Laghi, Western Southern Alps, large Permian granite plutons and mafic-intermediate stocks and dykes (Appinite suite) were emplaced in a post-collision environment. The magmatic rocks of Serie dei Laghi are metaluminous, and mainly exhibit petrographic and geochemical characters typical of medium-K calc-alkaline series. Granites and leucocratic \"Appinites\" show LREE and LILE enriched patterns and Nb, P, and Ti negative spikes typical of calc-alkaline series. In the mafic Appinite samples, the above characteristics become progressively less pronounced with decreasing acidity. The gabbro-noritic Appinites (Mg# = 67-75, Ni and Cr contents up to 163 ppm and 882 ppm, respectively) are the most primitive reported up to now among the Permian magmatic rocks from Southern Alps east of the Ivrea Verbano Zone. On the basis of their geochemical and isotope patterns, they can be considered with reasonable confidence as mantle derivatives that underwent very little, if any, crustal contamination. Their overall geochemical and isotope characteristics (eNd = 0.06/-2.45, (87Sr/86Sr)280 = 0.7044-0.7072), suggest an enriched mantle as the source of Serie dei Laghi magmatic series. Large-scale correlation of the whole rock series in the Nd and Sr covariation diagrams indicates the prominence of mantle-crust interaction in the evolution of the Permian plutonic rocks from Serie dei Laghi . The correlation between isotope ratios and SiO2 suggests evolution of the magmas in crustal chambers. The entire Permian intrusive series was generated through complex crust-mantle interaction mechanisms, starting from a mantle-derived magma isotopically similar to gabbro-noritic Appinites. The following frame can be depicted: a basaltic magma rising from the mantle resided in a magma chamber at the base of the crust and underwent combined assimilation and crystal fractionation (AFC): the amount of assimilated crust at this stage is about 10%. A late-orogenic transtensive regime allowed small magma batches to rise from the chamber directly to the surface, without further crustal exchange (Appinites). Continued magma input, crustal assimilation, crystallization, and tapping, extended the duration of the magma chamber until post-orogenic stage. Crustal extension permitted the formation of shallower magma chambers in which large volumes of hybrid magmas (Alzo-Roccapietra, Montorfano and Baveno-Mottarone plutons) rested and further assimilated crustal material (20-25%). (literal)

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