**2. Sampling and analytical techniques**

The sampling was performed in the entire area of the Smrekovec Volcanic Complex, although particularly detailed study has been carried out in two sections Krnes, and Smrekovec G34 (**Figure 2**). Lithofacies was determined by field observation, and chemical, mineralogical and petrographic analysis. Over 900 thin sections have been inspected in detail.

**305**

hydrothermal fluids (**Figure 3**).

calibration.

*Submarine Stratovolcano Peperite Syn-Formational Alteration - A Case Study of the Oligocene…*

were determined in whole-rock powdered samples. Clay minerals were analysed in oriented samples using slurries (<2 μm) dispersed on glass slides and undergoing standard procedures including air-drying and solvation in ethylene glycol. The XRD analysis was performed using a Philips diffractometer PW 3719 and a goniometer PW 1820, owned by the Department of Geology, Faculty of Natural Sciences and Technology, University of Ljubljana. Machine settings for all analysed samples were as follows: generator operated at 40 kV and 30 mA using CuKα radiation (wavelengths Kα1 = 1.54056 Å and Kα2 = 1.54439 Å), Ni filter, with automatic divergence slit and monochromator on. Scanning rate was 2°2*θ*/min; scanning range amounted to 2°2*θ* − 70°2*θ* for powdered samples and 2°2*θ* - 45°2*θ* for oriented samples. Digital data were processed using peak-fitting program X'Pert HighScore Plus 4.0. Semiquantitative analysis was performed by the program using the data base, internal standard rock samples and bulk chemical composition of powdered samples. Detailed mineral studies were performed on 9 polished thin sections using a scanning electron microscope (SEM) Jeol JSM-6490 equipped with an energy dispersive spectrometer (EDS) INCA Oxford 250, and located at Geological Survey of Slovenia. Elemental analyses were performed in thin sections having a thickness of 40 μm and uncovered polished upper surface, at accelerating voltage of 15 kV using a defocused electron beam of 20 μm in diameter, with a current of 10 nA and a counting time of 20 s. Synthetic and natural standards were used for

Chemical analysis of 150 bulk-rock samples of lavas and shallow intrusive bodies was performed in AcmeLabs, Vancouver, Canada, and Actlabs Activation Laboratories Ltd. Ontario, Canada. Major and trace elements were determined by a combination of X-ray fluorescence (XRF), inductively coupled plasma source (ICP)

In northern Slovenia, there are four large tectonic units: the Eastern Alps, the Southern Alps, the Outer Dinarides and the south-westernmost extending of the Tertiary system of Pannonian basins [28, 29] with the Smrekovec Volcanic Complex (**Figure 1**). The most outstanding geological structure is the Periadriatic Line (PAL), a complex regional fault system which represents in palinspastic reconstructions a shear zone developed by Late Cretaceous to Paleogene subduction of the European plate below the African plate [39, 40]. In the Eocene (~45 Ma) the subduction transformed into collision although the convergence continued during the Oligocene and resulted in break off of the southeast-dipping European slab

The related Oligocene (28-22 Ma) volcanic activity occurred in the Smrekovec Basin (**Figure 3**) that had been subsided within the Permian and Triassic clastic and carbonate successions [43]. Tertiary sedimentation began in Late Eocene in fluviatile, limnic and shallow-marine depositional environment and changed to outer neritic and bathyal during the Oligocene time [29, 43]. In a middle bathyal environment characterised by sedimentation of organic-rich clayey silts [43], simultaneous volcanic activity created a composite stratovolcano. Magmas had calc-alkaline and medium-K affinity and formed a suite ranging in composition from basaltic andesite to dacite [44–46]. Volcanic activity had entirely submarine character and after its cessation, the Upper Oligocene to Early Miocene (Egerian) sedimentation continued with fossiliferous marine clayey silt [29]. The stratovolcano hosted hydrothermal system with a deep igneous source and convective-advective flow of

beneath the Alps that generated magmatism along the PAL [41, 42].

and mass spectroscopy (MS) analytical techniques.

**3. Geological setting and the studied sections**

*DOI: http://dx.doi.org/10.5772/intechopen.95480*

Alteration minerals were analysed by X-ray diffraction (XRD) techniques in altogether 260 samples. Zeolites and related calcium aluminosilicate minerals

### *Submarine Stratovolcano Peperite Syn-Formational Alteration - A Case Study of the Oligocene… DOI: http://dx.doi.org/10.5772/intechopen.95480*

were determined in whole-rock powdered samples. Clay minerals were analysed in oriented samples using slurries (<2 μm) dispersed on glass slides and undergoing standard procedures including air-drying and solvation in ethylene glycol. The XRD analysis was performed using a Philips diffractometer PW 3719 and a goniometer PW 1820, owned by the Department of Geology, Faculty of Natural Sciences and Technology, University of Ljubljana. Machine settings for all analysed samples were as follows: generator operated at 40 kV and 30 mA using CuKα radiation (wavelengths Kα1 = 1.54056 Å and Kα2 = 1.54439 Å), Ni filter, with automatic divergence slit and monochromator on. Scanning rate was 2°2*θ*/min; scanning range amounted to 2°2*θ* − 70°2*θ* for powdered samples and 2°2*θ* - 45°2*θ* for oriented samples. Digital data were processed using peak-fitting program X'Pert HighScore Plus 4.0. Semiquantitative analysis was performed by the program using the data base, internal standard rock samples and bulk chemical composition of powdered samples.

Detailed mineral studies were performed on 9 polished thin sections using a scanning electron microscope (SEM) Jeol JSM-6490 equipped with an energy dispersive spectrometer (EDS) INCA Oxford 250, and located at Geological Survey of Slovenia. Elemental analyses were performed in thin sections having a thickness of 40 μm and uncovered polished upper surface, at accelerating voltage of 15 kV using a defocused electron beam of 20 μm in diameter, with a current of 10 nA and a counting time of 20 s. Synthetic and natural standards were used for calibration.

Chemical analysis of 150 bulk-rock samples of lavas and shallow intrusive bodies was performed in AcmeLabs, Vancouver, Canada, and Actlabs Activation Laboratories Ltd. Ontario, Canada. Major and trace elements were determined by a combination of X-ray fluorescence (XRF), inductively coupled plasma source (ICP) and mass spectroscopy (MS) analytical techniques.
