Cariddi, Bruna (2022) The Cenozoic magmatic activity in Sardinia: chronology and geodynamic significance. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: English
Title: The Cenozoic magmatic activity in Sardinia: chronology and geodynamic significance
Date: 9 March 2022
Number of Pages: 232
Institution: Università degli Studi di Napoli Federico II
Department: Scienze della Terra, dell'Ambiente e delle Risorse
Dottorato: Scienze della Terra, dell'ambiente e delle risorse
Ciclo di dottorato: 34
Coordinatore del Corso di dottorato:
Date: 9 March 2022
Number of Pages: 232
Keywords: Calcalkaline magmatism; Sardinia
Settori scientifico-disciplinari del MIUR: Area 04 - Scienze della terra > GEO/07 - Petrologia e petrografia
Date Deposited: 18 Mar 2022 08:46
Last Modified: 28 Feb 2024 10:25

Collection description

The Cixerri, Siliqua, Punta Su Silixianu and Monastir lava domes are some of the igneous products with calcalkaline affinity and orogenic features of Cenozoic age cropping out in western Sardinia. The new 40Ar/39Ar dating performed in this study confirm the wide time span of the subduction-related igneous activity in Sardinia, with a peak at 22-18 Ma when many lava domes were emplaced in the Cixerri half-graben. The rocks vary from basaltic andesite to dacite. The Monte Nureci intrusive rocks are olivine gabbronorites and gabbronorites. The major and trace element variations in the studied rocks of various districts point to a magmatic evolution driven by fractional crystallization of plagioclase, olivine, pyroxenes and opaque oxides. The thermobarometer results and the petrographic study indicate that the evolution took place in polybaric feeding system interested by phenomena like magma recharge/mixing and/or variations of pressure, temperature and H2O content. Mass balance calculations and trace element variations indicate that amphibole is the main mafic phase crystallizing in the Cixerri magma, due to its high H2O content (4-9 wt.%). The chemical composition of Acquafredda lava dome (Siliqua district), with high Sr/Y (70-90), LaN/YbN (>20) and low HREE contents (HREE<10 times chondrite), reveals the occurrence of dacites with adakitic signature, never found on the Island before. The different trace element concentration in the rocks of the various districts is indicative of primitive magmas heterogeneity and of variable fluid flux from the subducted slab and sediments to the mantle wedge under the volcanic arc in Sardinia. The Monte Nureci intrusive rocks are cumulates of the Arcuentu magmas in the basaltic andesite to andesite range, as confirmed by Sr-Nd isotopes and mineral chemistry. The isotopic variations observed in each district (e.g. Cixerri: 87Sr/86Sri=0.70701-0.70786 and 143Nd/144Ndi=0.512328-0.512436; Siliqua: 87Sr/86Sri=0.70599-0.70682 and 143Nd/144Ndi=0.512379-0.512482; Arcuentu: 87Sr/86Sri=0.70538-0.71127 and 143Nd/144Ndi=0.512172-0.51268) evidence that magma evolution occurred in open systems with crustal assimilation, it was of different intensity due to the independence of magma feeder systems in each district.


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