SHRIMP U-Pb Zircon Triassic Intrusion Age of the Finero Mafic Complex (Ivrea-Verbano Zone, Western Alps) and its Geodynamic Implications

Zanetti, A.; Mazzucchelli, Maurizio; Sinigoi, S.; Giovanardi, Tommaso; Peressini, G.; Fanning, Mark C.

doi:10.1093/petrology/egu018

Cited by 24 publications

(78 citation statements)

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“…Lu et al [5] suggested instead a hydrous tholeitiic to transitional MORB composition as parent melt. The same geochemical affinity was proposed by Zanetti et al [8] for the parent melts of the External Gabbro unit (EG) within the Finero Mafic Complex. All authors agree that the amphibole was an early liquidus phase during the crystallization of the complex.…”

Section: Introductionsupporting

confidence: 73%

“…Siena & Coltorti [3] suggest that its crystallization occurred after plagioclase segregation. Consistently, Zanetti et al [8] document that, in the EG unit, amphibole crystallized as an interstitial phase after pyroxenes and plagioclase precipitation. In contrast to the Finero mantle massif, the occurrence of phlogopite in the Finero Mafic Complex has not yet been properly recognized and studied.…”

Section: Introductionmentioning

confidence: 64%

“…It consists of mafic, and subordinately ultramafic, rocks (comprising the following units: the Lay-ered Internal Zone unit, the Amphibole-Peridotite unit and the External Gabbro unit) surrounding a completely metasomatized mantle massif ( Figure 1; [1][2][3][4][5][6][7][8][9] and references therein). The metasomatized mantle massif, named the PhlogopitePeridotite unit (Ph-Pd; unit names and acronyms according to Siena & Coltorti [3]) by Cawthorn [1], is mainly composed of phlogopite-bearing amphibole harzburgite that contains secondary orthopyroxene, amphibole, phlogopite and clinopyroxene that segregated from metasomatizing melts/fluids.…”

Section: Introductionmentioning

confidence: 99%

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Occurrence of phlogopite in the Finero Mafic layered complex

Giovanardi¹,

Mazzucchelli²,

Zanetti

et al. 2014

Open Geosciences

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Phlogopite-bearing lithologies are the main constituent of the Phlogopite-Peridotite unit of the Finero sequence and the result of pervasive migration of metasomatizing melts/fluids. Conversely, the presence of phlogopite within the associated Finero Mafic Complex, a mafic-ultramafic pluton intruded into the metamorphic basement of the Adria plate, is mentioned in literature as rare. Recent detailed fieldwork has evidenced the presence of two distinct phlogopite-rich ultramafic lithologies within the Amphibole-Peridotite unit of the Finero Mafic Complex, where phlogopite is always associated with amphibole. Field and petrographic features of these occurrences, as well as major-and trace-element mineral chemistry, are here presented to i) place constraints on the nature of the parent melt from which they have been generated and ii) to address their relationship with the other lithologies of the Finero Complex. We find that these rocks were formed by late melt migrations along shear zones under high-T conditions. The geochemical affinity of these lithologies is different to the tholeiitic-transitional affinity reported in literature for the Finero Mafic Complex. The enrichment in LREE, Th, U and Sr of the associated amphibole possibly suggests that these phlogopite-bearing lithologies are genetically related to the metasomatic events that have affected the Finero mantle massif.

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Section: Introductionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

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Occurrence of phlogopite in the Finero Mafic layered complex

Giovanardi¹,

Mazzucchelli²,

Zanetti

et al. 2014

Open Geosciences

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“…In the northeastern and southwestern parts of the Ivrea Zone, some samples show an age generation < 220 Ma (Zanetti et al 2013;Schaltegger et al 2015;Langone et al 2017) we have found no evidence for that in Val Strona di Omegna (Fig. S9 Online Resource 3).…”

Section: Implications For the Interpretation Of The Metamorphic Evolumentioning

confidence: 63%

“…The main intrusive phase has been dated on zircon by Peressini et al (2007) at 288 ± 4 Ma, with locally earlier magmatic activity at ~ 295 Ma (Sinigoi et al 2011) and 314 ± 5 Ma (Klötzli et al 2014). In the northern part of the Ivrea Zone, the Finero mafic-ultramafic body is characterised by a range of Permian U-Pb zircon dates as well as younger zircon intrusion ages of 232 ± 3 Ma and late fluid-related recrystallisation between ~ 220 and 200 Ma (Zanetti et al 2013;Schaltegger et al 2015;Langone et al 2017).…”

Section: Geological Settingmentioning

confidence: 99%

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

Kunz

Regis

Engi

2018

Contrib Mineral Petrol

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Granulite facies rocks frequently show a large spread in their zircon ages, the interpretation of which raises questions: Has the isotopic system been disturbed? By what process(es) and conditions did the alteration occur? Can the dates be regarded as real ages, reflecting several growth episodes? Furthermore, under some circumstances of (ultra-)high-temperature metamorphism, decoupling of zircon U-Pb dates from their trace element geochemistry has been reported. Understanding these processes is crucial to help interpret such dates in the context of the P-T history. Our study presents evidence for decoupling in zircon from the highest grade metapelites (> 850 °C) taken along a continuous high-temperature metamorphic field gradient in the Ivrea Zone (NW Italy). These rocks represent a well-characterised segment of Permian lower continental crust with a protracted high-temperature history. Cathodoluminescence images reveal that zircons in the mid-amphibolite facies preserve mainly detrital cores with narrow overgrowths. In the upper amphibolite and granulite facies, preserved detrital cores decrease and metamorphic zircon increases in quantity. Across all samples we document a sequence of four rim generations based on textures. U-Pb dates, Th/U ratios and Ti-in-zircon concentrations show an essentially continuous evolution with increasing metamorphic grade, except in the samples from the granulite facies, which display significant scatter in age and chemistry. We associate the observed decoupling of zircon systematics in high-grade non-metamict zircon with disturbance processes related to differences in behaviour of non-formula elements (i.e. Pb, Th, U, Ti) at high-temperature conditions, notably differences in compatibility within the crystal structure.

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The deformation record of olivine in mylonitic peridotites from the Finero Complex, Ivrea Zone: Separate deformation cycles during exhumation

Matysiak

Trepmann

2015

Tectonics

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Mylonitic peridotites from the Finero complex are investigated to detect characteristic olivine microfabrics that can resolve separate deformation cycles at different metamorphic conditions. The heterogeneous olivine microstructures are characterized by deformed porphyroclasts surrounded by varying amounts of recrystallized grains. A well-developed but only locally preserved foam structure is present in recrystallized grain aggregates. This indicates an early stage of dynamic recrystallization and subsequent recovery and recrystallization at quasi-static stress conditions, where the strain energy was reduced such that a reduction in surface energy controlled grain boundary migration. Ultramylonites record a renewed stage of localized deformation and recrystallization by a second generation of recrystallized grains that do not show a foam structure. This second generation of recrystallized grains as well as sutured grain and kink band boundaries of porphyroclasts indicate that these microstructures developed during a stage of localized deformation after development of the foam structure. The heterogeneity of the microfabrics is interpreted to represent several (at least two) cycles of localized deformation separated by a marked hiatus with quasi-static recrystallization and recovery and eventually grain growth. The second deformation cycle did not only result in reactivation of preexisting shear zones but instead also locally affected the host rock that was not deformed in the first stage. Such stress cycles can result from sudden increases in differential stress imposed by seismic events, i.e., high stress-loading rates, during exhumation of the Finero complex.

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SHRIMP U-Pb Zircon Triassic Intrusion Age of the Finero Mafic Complex (Ivrea-Verbano Zone, Western Alps) and its Geodynamic Implications

Cited by 24 publications

References 0 publications

Occurrence of phlogopite in the Finero Mafic layered complex

Occurrence of phlogopite in the Finero Mafic layered complex

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

The deformation record of olivine in mylonitic peridotites from the Finero Complex, Ivrea Zone: Separate deformation cycles during exhumation

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