FluidNET Science Conference Abstract - Preliminary fluid inclusion data from the Amp-gabbronorites of Ivrea town, Lower Mafic Complex, Ivrea-Verbano Zone
Creators: name: Stylianos Karastergios
name: Maria L. Frezzotti
name: Rosario Esposito
name: Simona Ferrando
Publisher: name: Zenodo
Year: 2024

description: Preliminary fluid inclusion data from the Amp-gabbronorites of Ivrea town, Lower Mafic Complex, Ivrea-Verbano Zone

 

Stylianos Karastergios*1, Maria L. Frezzotti1, Rosario Esposito1 and  Simona Ferrando2 

1Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.za Della Scienza 4, 20126 Milano, Italy

2Department of Earth Sciences, University of Torino, Via Valperga Caluso, 35, 1-10125 Torino, Italy

*Corresponding author’s contact details (s.karastergios@campus.unimib.it)

 

The Ivrea Verbano Zone (IVZ) is a continental crust section located in the Southalpine domain of the Alps (NW Italy) recording late-stage Variscan metamorphism and igneous activity. The two main lithostratigraphic units in the IVZ are the metamorphic basement, called the Kinzigite Formation (KF), composed of metabasites and metapelites ranging from amphibolite to granulite-facies metamorphism and the Mafic Complex (MC), a gabbroic batholith that was emplaced at the base of the continental crust following the peak metamorphic event in the KF.

 

Recent studies have proven the existence of contemporaneous and immiscible melt (MI) and fluid (C-O-H) inclusions (FI) in the Grt-bearing migmatites from the KF (Carvalho et al., 2019). However, little attention has been given to the FI in the deep crustal rocks derived from the intrusion of the MC. The studied lithologies are Amp-gabbronorites which is the most common lithology in the Lower Mafic Complex (LMC). The Amp-gabbronorites are characterized by medium to coarse-grained granoblastic texture with triple joints, due to slow cooling in the lower crust. In this study we report the existence of carbonic multiphase inclusions (MFI) from the Amp-gabbronorites of the LMC located in the area of Ivrea town.

The FI are ubiquitous in Opx and Amp and show mainly a primary distribution (i.e., isolated large inclusions and clusters) with negative crystal shapes. The size in Opx and Amp varies from 5-10 μm, however, elongated inclusions can reach 20 μm in length and 5-7 μm in width. Opx contains biphase FI consisting of carbonic fluid and one birefringent mineral phase. Raman microspectroscopy shows that the FI in Opx consist of pure CO2 and Mg-Calcite (main vibration at 1088 cm-1). MFI from Amp show one or two birefringent phases. Preliminary data show anatase (main vibration at 143 cm-1) and dolomite (main vibration at 1095 cm-1), in the absence of any fluid phase. The CO2 density was calculated using the Raman densimeter equation of Remigi et al. (2021): d = -0.01472000*Δ3 + 4.51148969*Δ2 -460.27795107*Δ + 15631.28847817 (R2= 0.994, SE= ±0.015 g/cm3), where Δ, is the distance between the CO2 upper and lower bands, as they were calculated from the Raman spectrum using a pseudovoight fitting. The calculated densities vary from 0.52–0.74 g/cm3; these values are probably underestimated due to the presence of Mg-calcite in the FI. Further investigation in the other minerals of the assemblage (e.g., Pl and Cpx) will provide an integrated view of the composition of the fluids and solids included in the Amp-gabbronorites.

 

References:

Carvalho, B. B., et al. (2019). Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy). J Metamorph Geol, 37(7), 951–975. https://doi.org/10.1111/jmg.12463

Remigi, S. et al. (2021). Interlaboratory Application of Raman CO2 Densimeter Equations: Experimental Procedure and Statistical Analysis Using Bootstrapped Confidence Intervals. Applied Spectroscopy, 75(7), 867–881. https://doi.org/10.1177/0003702820987601

 

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 956127