Laurite and zircon from the Finero chromitites (Italy): New insights into evolution of the subcontinental mantle

Malitch, K. N.; Белоусова, Е. А.; Griffin, William L.; Badanina, I. Yu.; Knauf, V. V.; O’Reilly, Suzanne Y.; Pearson, Norman J.

doi:10.1016/j.oregeorev.2017.06.027

Cited by 20 publications

(7 citation statements)

References 88 publications

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“…The obtained U-Pb data perfectly overlaps the major age peak (about 187 Ma) of zircon from chromitite layers within the mantle peridotites interpreted as the timing of exhumation at crustal levels [19]. Triassic-Jurassic U-Pb zircon ages were also reported for other mantle chromitites [48] and leucocratic dykes (225 ± 13 Ma: [27]; 190-212 Ma: [34]); they were interpreted as due to prolonged formation and multistage zircon growth in the chromitites and the timing of intrusion for the dykes, respectively. It is difficult to constrain the origin of the zircon grain analyzed in the present study based only on the U-Pb data.…”

Section: Timing Of Deformationsupporting

confidence: 74%

“…Two LA-ICP-MS spots on this zircon provided one concordant U-Pb age at 187±3 Ma (Figure 10c) and a second discordant one (3.5% discordance) with a 206 Pb/ 238 U age of 180±4 Ma (Figure 10c and Table 5). Zircon has been observed as accessory in different lithologies within the Ph-Pd, i.e., chromitites [19,26,48] and leucocratic dykes/pods/pegmatites [26,27]. The studied zircon was possibly inherited from one of these lithologies affected by shearing.…”

Section: Timing Of Deformationmentioning

confidence: 93%

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Porphyroclasts: Source and Sink of Major and Trace Elements During Deformation-Induced Metasomatism (Finero, Ivrea-Verbano Zone, Italy)

et al. 2020

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Petrographic and geochemical data for mylonites from a metric-scale shear zone in mantle peridotites from the Finero massif (Southern Alps) record large mineralogical and geochemical modifications compared to surrounding coarse-grained ultramafic rocks, which were pervasively deformed in presence of hydrous melts. The mylonites are composed by olivine and orthopyroxene and, less frequently, clinopyroxene, phlogopite, and pargasite porphyroclasts enclosed in a fine-grained matrix of phlogopite and olivine, with subordinate amounts of orthopyroxene, clinopyroxene, pargasite, and chromite. P-T estimates indicate that deformation occurred under granulite- to upper-amphibolite facies conditions. Field relationships and U-Pb dating indicate that the shear zone was active during Lower Jurassic and/or later, in an extensional setting at the western margin of the Adria plate, which led to the opening of the Alpine Tethys. The major and trace element composition of the porphyroclasts in the mylonites significantly differ from those in the hosting coarse-grained ultramafics. Porphyroclasts were chemically active during deformation acting as source (diffusion-out) or sink (diffusion-in) for some trace elements. The chemical modifications were promoted by the interaction with aqueous fluids and the composition varied from mantle- (enriched in Ni, Co, Li, Na, REE, Y, and Sr) to crustal-derived (enriched in Zn, K, Al, Ti, and Fe).

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Section: Timing Of Deformationsupporting

confidence: 74%

Section: Timing Of Deformationmentioning

confidence: 93%

Porphyroclasts: Source and Sink of Major and Trace Elements During Deformation-Induced Metasomatism (Finero, Ivrea-Verbano Zone, Italy)

et al. 2020

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“…A minor age peak at ~208 Ma was also observed by Malitch et al. (2017) in zircon from Finero chromitites at Rio Creves. It is noted that the phlogopite ages may not represent magmatic crystallization ages, but thermal resetting of earlier‐crystallized phlogopite during later regional high‐temperature events.…”

Section: Discussionsupporting

confidence: 76%

On the formation of magmatic sulphide systems in the lower crust by long‐lived mass transfer through the lithosphere: Insights from the Valmaggia pipe, Ivrea Verbano Zone, Italy

et al. 2020

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The lower crustal domain of the Ivrea‐Verbano Zone (NW Italy) hosts five ~300‐m‐wide pipe‐like ultramafic intrusions that are metasomatized and exhibit Ni‐Cu‐PGE sulphide mineralization. To better constrain the role of metasomatism in the ore genesis, we studied the best‐preserved pipe at Valmaggia which was emplaced 249 Myrs ago. Phlogopite 40Ar/39Ar analyses show that the pipe was infiltrated by metasomatic fluids derived from the subcontinental lithospheric mantle (SCLM) in two pulses at ~208 Ma and ~189 Ma which introduced sulphides into the pipe. Consequently, the pipe repeatedly acted as a preferred path for mass transfer from the SCLM into the lower crust over >60 Myrs (i.e., emplacement to second metasomatic pulse). Uplifted block margins, such as the Ivrea‐Verbano Zone, are potentially important exploration targets for magmatic sulphides. We argue that exploration strategies should focus on structures such as pipes that can focus metasomatic agents during ascent through the lithosphere.

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“…Zircons with age and ε Hf(t) akin to those of the VM1 zircons and VF33 group 1 zircons occur in metasomatic chromitite layers within amphibole-phlogopite mantle peridotites of the Ivrea zone ( Fig. 3G; Zanetti et al, 2016;Malitch et al, 2017), indicating that the studied carbonatites isotopically match parts of the mantle. Available bulk Sr-Nd isotope data for the Ivrea alkaline intrusions present a large scatter (Stähle et al, 2001;Garuti et al, 2001) fitting the spread in mantle rocks (Voshage et al, 1987).…”

Section: Magma Sourcementioning

confidence: 94%

Jurassic carbonatite and alkaline magmatism in the Ivrea zone (European Alps) related to the breakup of Pangea

Galli

Grassi

Sartori

et al. 2019

Geology

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We report on pipe-like bodies and dikes of carbonate rocks related to sodic alkaline intrusions and amphibole mantle peridotites in the Ivrea zone (European Southern Alps). The carbonate rocks have bulk trace-element concentrations typical of low-rare earth element carbonatites interpreted as cumulates of carbonatite melts. Faintly zoned zircons from these carbonate rocks contain calcite inclusions and have trace-element compositions akin to those of carbonatite zircons. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon dating yields concordant ages of 187 ± 2.4 and 192 ± 2.5 Ma, coeval with sodic alkaline magmatism in the Ivrea zone. Cross-cutting relations, ages, as well as bulk and zircon geochemistry indicate that the carbonate rocks are carbonatites, the first ones reported from the Alps. Carbonatites and alkaline intrusions are comagmatic and were emplaced in the nascent passive margin of Adria during the Early Jurassic breakup of Pangea. Extension caused partial melting of amphibole-rich mantle domains, yielding sodic alkaline magmas whose fractionation led to carbonatite-silicate melt immiscibility. Similar occurrences in other rifts suggest that small-scale, sodic and CO 2-rich alkaline magmatism is a typical result of extension and decompressiondriven reactivation of amphibole-bearing lithospheric mantle during passive continental breakup and the evolution of magma-poor rifts.

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Laurite and zircon from the Finero chromitites (Italy): New insights into evolution of the subcontinental mantle

Cited by 20 publications

References 88 publications

Porphyroclasts: Source and Sink of Major and Trace Elements During Deformation-Induced Metasomatism (Finero, Ivrea-Verbano Zone, Italy)

Porphyroclasts: Source and Sink of Major and Trace Elements During Deformation-Induced Metasomatism (Finero, Ivrea-Verbano Zone, Italy)

On the formation of magmatic sulphide systems in the lower crust by long‐lived mass transfer through the lithosphere: Insights from the Valmaggia pipe, Ivrea Verbano Zone, Italy

Jurassic carbonatite and alkaline magmatism in the Ivrea zone (European Alps) related to the breakup of Pangea

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