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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, northwestern Italy)

Laura Pinarelli, Aldo Del Moro, Attilio Boriani and Valeria Caironi
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, northwestern Italy)
European Journal of Mineralogy (April 2002) 14 (2): 403-415

Abstract

In the 'Serie dei Laghi', large Permian granite plutons and mafic-intermediate stocks and dykes (the 'appinite suite') were emplaced in a post-collision environment. These magmatic rocks are metaluminous and show petrographic and geochemical characters typical of medium-K, calc-alkaline series, with LREE and LILE enriched patterns and negative Nb, P and Ti anomalies. The gabbro-noritic appinites (mg 67-75, Ni and Cr contents of 163 and 882 ppm, respectively) are the most primitive of the Permian magmatic rocks reported in the S Alps E of the Ivrea Verbano zone. They can be considered mantle derivatives that underwent little, if any, crustal contamination. The strong overall correlation of the whole-rock series in Nd and Sr covariation diagrams indicates the presence of mantle-crust interactions in the evolution of these rocks. It is envisaged that 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, the amount of assimilated crust being approximately 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 magmatic input, crustal assimilation, crystallization and tapping extended the duration of the magma chamber up until the post-orogenic stage, enabling shallower magma chambers to produce large volumes of hybrid magmas with 20-25% assimilated crustal material.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 14
Serial Issue: 2
Title: 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, northwestern Italy)
Affiliation: Centro di Studio per la Minerogenesi e la Geochimica Applicata, Florence, Italy
Pages: 403-415
Published: 200204
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 29
Accession Number: 2002-027813
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
N36°30'00" - N47°30'00", E06°30'00" - E19°00'00"
Secondary Affiliation: Istituto di Geocronologia e Geochimica Isotopica, ITA, ItalyUniversita di Milano, ITA, Italy
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200210
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