Descrizione: Descrizione: Descrizione: EGU Summer School 2023

 

 

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    Program

·         Timetable

·         Field program (Neves area): August 21st to 24th

·         Lecture program Bruneck (Brunico): August 24th to 28th

 

    Timetable    21-28 August 2023

    • August 21st afternoon (16.00): arrival at Bruneck (Brunico) train station and transfer to the Chemnitzerhütte (Rifugio Porro) for dinner and overnight
    • August 22nd-23th : field work on the glaciated outcrops in front of the Grosser Möseler (Mesule) glacier (photo)
    • August 24th morning: move to Bruneck (Brunico)
    • August 24th-27th: classroom teaching in Bruneck (Brunico)
    • August 28th morning: depart

 

Field Program

The field course will be held in the Nevessee (Lago di Neves) area (South Tyrol, northeast Italy) and will address the structural analysis of deformation structures within the Tauern meta-granitoids. The structures are present on polished outcrops at the base of the south-eastern Grosser Möseler (Mesule) glacier (Fig. 1, Fig. 2) that provide spectacular exposures for structural analysis of 2D deformation geometries. The area is located at about 2600 m and is reachable by a well-marked track from the Chemnitzerhütte (Rifugio Porro), at 2419 m. We will stay at this hut, which one reaches along a broad path from the Nevessee in about 1 hr 45 mins walking time (about a 500 m climb).
From the geological point of view, the area is located just north of a thick belt of Alpine amphibolite facies mylonites (well visible on the aerial photograph of Fig. 3), which can be investigated along the path from the hut to the glacier. The study area represents a low strain domain, which largely escaped the Alpine structural overprint. It is therefore possible to analyse in detail the progressive development of discrete ductile shear zones that exploit a network of brittle precursors (joints) and pre-existing magmatic or fluid–induced compositional heterogeneities.
During the field analysis, students will gain familiarity with the following structures:

·         magmatic structures (including different acid and basic intrusives, magma mingling, etc.): Fig. 4a, Fig. 4b, Fig. 4c, Fig. 4d, Fig. 4e);

·         joints;

·         epidote veins and alteration haloes along joints and fractures (Fig. 5a, Fig. 5b, Fig. 5c);

·         single and paired discrete shear zones nucleating on planar compositional and structural heterogeneities (Fig. 6a, Fig. 6b, Fig. 6c, Fig. 6d, Fig.6e , Fig.6f, Fig.6g);

·         quartz-biotite-plagioclase-biotite-calcite veins (Fig. 7a, Fig. 7b, Fig. 7c);

·         intersecting ductile shear zones (Fig. 8a, Fig. 8b, Fig. 8c).

·         late stage quartz-chlorite-epidote vein systems (Fig. 9a, Fig. 9b, Fig. 9c).

See all the pictures !!!

Suggested reading:

·         Mancktelow, N.S. and Pennacchioni, G., 2005. The control of precursor brittle fracture and fluid–rock interaction on the development of single and paired ductile shear zones. Journal of Structural Geology 27, 645–661. PDF


·         Mancktelow, N.S. and Pennacchioni, G., 2010. Why calcite can be stronger than quartz. Journal of Geophysical Research 115, B01402, doi:10.1029/2009JB006526. PDF


·         Pennacchioni, G. and Mancktelow, N.S., 2007. Nucleation and initial growth of a shear zone network within compositionally and structurally heterogeneous granitoids under amphibolite facies conditions. Journal of Structural Geology 29, 1757-1780. PDF


·         Mancktelow, N. S., and Pennacchioni, G., 2013. Late magmatic healed fractures in granitoids and their influence on subsequent solid-state deformation. Journal of Structural Geology 57, 81-96.


·         Pennacchioni, G., and Mancktelow, N. S., 2013. Initiation and growth of strike-slip faults within intact metagranitoid (Neves area, eastern Alps, Italy). Geological Society of America Bulletin, 125, 1468-1483.


·         Pennacchioni, G., Ceccato, A., Fioretti, A.M., Mazzoli, C., Zorzi, F. and Ferretti, P., 2016. Episyenites in meta-granitoids of the Tauern Window (Eastern Alps): unpredictable?Journal of Geodynamics, 101, 73-87.


·         Pennacchioni, G., Mancktelow, N.S., 2018. Small-scale ductile shear zones: Neither extending, nor thickening, nor narrowing.Earth-Sciences Reviews, 184, 1-12.

 


Students will be taught to analyse:

·         the time relationships between the different intrusions of the pre-Alpine protolith;

·         the control of structural and compositional heterogeneities on nucleation of shear zones;

·         the role of fluids during ductile deformation;

·         the kinematic relationships between the different structural element of the deformation network (shear zones and veins);

·         the interference between intersecting shear zones;

·         geometry and linkage of brittle faults developed during exhumation.

Lecture Program

The second part of the school will include a series of lectures The classes will cover the following topics:

1) Solid-state ductile deformations within cooling of plutons.
Teacher: Giorgio Pennacchioni ( University of Padova, Italy)

The lecture will describe the solid-state deformation structures developed in different plutons (e.g.: Adamello, Southern Alps, Italy; Mono Pass Intrusive Suite, Sierra Nevada, California) during their cooling. The main focus will be on deformation structures developed at  high temperatures (T ≥ 500°C) and the role of structural (joints) and compositional (e.g. dykes) heterogeneities on nucleation of shear zones. The deformation structures in  cooling plutons will be compared with those seen during the field excursion in the Tauern metagranitoids in the Neves area. These observations provide the basis of a new model for the nucleation of ductile shear zones in granitoid plutons.

2) Fluid rock interaction in faults and shear zones.
Teacher: Vénice Akker (ETH-Zurich, Switzerland)

(a) Physical effects of fluids on strength and mechanical behaviour of faults and shear zones
(b) Coupling between deformation and permeablity in faults and shear zones (from the nm- to the km-scale).
(c) Deciphering fluid properties at depth from vein geochemistry, including introduction to Synchrotron X-Ray Fluorescence Microscopy.
(d) Fluid-rock interaction on the grain-scale, metamorphic reactions, pressure solution and recrystalization.

3) Deformation mechanisms and strain weakening in natural shear zones.
Teachers: Luca Menegon (University of Oslo, Norway) and Alberto Ceccato (ETH Zurich, Switzerland )

      The lecture will show examples of deformation microstructures of quartz and feldspars in natural shear zones formed at mid- to lower-crustal conditions. The observations will be discussed in terms of (i) the effect of fluid rock interaction on the activation of different deformation mechanisms, and (ii) the implications for the strength evolution of the mid- to lower crust. The following topics will be addressed:
(a) Effect of hydrous fluids on the creep strength and deformation microstructures of quartz: comparison between "wet" and "dry" quartz
(b) Fluids, replacement reactions and deformation in granitoids
(c) Grain size reduction and transition to diffusion creep deformation in (ultra)mylonites: rheological implications

4) Rock analogue and numerical modelling of shear zone structures.
Teacher: Neil Mancktelow (ETH-Zurich, Switzerland)

(a) Strain localization and the development of heterogeneous shear zones
(b) Shear zone ends and transfer zones
(c) Stress refraction in layered and anisotropic rocks
(d) Tectonic variation in pressure in deforming rocks and its importance for controlling fluid-rock interaction
(e) Flanking structures developed around planar heterogeneities in shear zones
(f) Deformation and rotation and/or stabilization of clasts in shear zones

5) Introduction to Finite Element Modelling in Geoscience .
Teacher: Dani Schimd (Oslo University, Norway )

6) Long-term creep and transient high-stress deformation in swismically active shear zones - shear zones, experiments and microstructures
Teacher: Claudia Trepmann (Ludwig-Maximilians University of Munich, Germany)

The lecture will address how microstructures can be used to obtain information on the stress history. Microstructures (SEM/EBSD and TEM) from kick-cook experiments (Griggs deformation apparatus) will be compared to microstructures from shear zone rocks in the view of the following topics:

(a) High-stress deformation versus high-strain deformation.
(b) Evidence of transient high stresses characteristic for coseismic deformation at or just below the days of the seismogenic zone.
(c) Stress-loading rates of how transient high stresses be built up at the rocks undergo creep during intersesimic periods.

6)  Role of chemical processes on strain localisation
Teacher: Philippe Goncalves (Université de Bourgogne Franche-Comté)

The aim of this lecture is to discuss the role of metamorphic and metasomatic reactions on the process of strain localisation. Using various natural examples coming from the Alps, including the Neves area, we will describe the mineralogical and chemical change involved from the early shear zone nucleation stage to the mature stage. These changes, as well as the P-T conditions of the deformation, will be modeled using phase equilibria modeling (pseudosections). All these results and observations will be used to determine how chemical and mechanical processes interact during the formation of a shear zone.

7)  Crystallographic preferred orientations and CPO-derived physical properties of rocks
Teacher: Luiz F. G. Morales (ETH Zurich - Scientific Center for Optical and Electron Microscopy)

The aim of this lecture is to present information about the development of crystallographic preferred orientation (CPOs) in geological materials, with examples, in quartz and calcite. The following topics will be addressed:

(a)   Mechanisms of formation of crystallographic preferred orientation in Earth's materials
(b)  CPO examples of quartz in nature and experiments
(c)  CPO examples of calcite in nature and experiments

Practical exercises:
-Calculation and plot of CPO of quartz and elasticity-derived properties using MTEX toolbox for Matlab (laptops with Matlab 2014 or later needed)

      

8) Structural dat analysis from photogrammetric outcrop models.
Teacher: Silvia Mittempergher (University of Modena and Reggio Emilia, Italy)

Photogrammetric outcrop models nowadays are easy to obtain thanks to the wide accessibility of high-quality cameras and drones, and increasing computational efficiency of SFM (Structure From Motion) photogrammetric softwares. However, extracting useful structural data is still a bottleneck and significantly limiting the full exploitation of the technique. The lecture will focus on:


(a) Introduction for the principles of photogrammetric reconstruction of rock outcrops
(b) Review of the main procedures and softwares for structural data extraction from the different outputs of a photogrammetric reconstruction (point clouds, rectified images, textured meshes).
(c) Application of image analysis techniques to improve the efficiency for lineament extraction from 3D models of smooth outcrops (examples from the glacier-outcrops of the Adamello and Neves areas).

 

Further Information

o    The field area is easy of access and no climbing or special Alpine experience is required. However, the field course is in a high mountain environment and adequate equipment is essential. What do you need? Download the checklist!
The work area is at 2600m a.s.l. We will be outside the whole day (with a packed lunch provided by the hut). The weather can be warm and sunny but can also be very cold, windy and, in the worst case, snowy.

o    Course language: English.

o    Course participants: priority is given to PhD students, post-Docs and young researchers specializing in structural geology. Finishing masters students in the process of starting PhD will be considered if there are places left.

o    Course max number of participants: 35 (on a first come first served basis).


Webmaster: Nicola Praticelli (Dept. of Geosciences - University of Padova - Italy)

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Sixth EGU Summer School