Course goals

By the end of the course the student will be able to:

• • understand the principles of rock deformation within shallow and deep parts of continental crust 

  • recognize and interpret brittle and ductile deformation structures 

  • understand the principles of metamorphism and identify metamorphic minerals. 

  • analyze orogenic and basin forming processes, and have knowledge on their controlling factors 

  • has the theoretical background to do basic geological fieldwork in deformed and/or metamorphic areas 

  • is able to relate geologic observations and earth observation data to tectonic processes

Content

Content
The course covers five distinct themes (structural concepts, shallow structures, deep structures, metamorphic concepts, deformation and metamorphism in the crust (introduction to tectonics)) with strong interconnections. These themes are relevant to contemporary Earth science issues related to subsurface exploitation (geothermal energy, CO2 storage, resources) and hazards (natural or induced earthquakes).
 

Lectures

First lecture: Introduction to the structure, objectives and content of the course. Overview of the lectures, practicals, expected deliverables and important deadlines.

Structural Concepts 1
Deformation phenomena at different scales: from hand specimen to orogen-scale. Basic concepts of continuous, ductile deformation: effect of the observation scale, concept of homogeneous deformation. Deformation as a combination of translation, rotation, and strain. Longitudinal and shear strain.
Description of deformation as a linear transformation, concept of the strain ellipse. Fundamentals of pure versus simple shear deformation. Required literature: HF Ch. 2
Fundamental laws describing the behaviour of earth materials. HF Ch. 6

Structural Concepts 2
Basic concepts of Stress: Shear and normal stress, Mohr circle and Mohr-Coulomb criterion, the role of fluid pressure and effective stress, Andersonian fault classification. Stress and stress regimes in the lithosphere.
Required literature: HF Ch. 4 pp. 73-81, Ch. 5, Ch. 7 pp.124-133, rest of Ch. 7 excluded, Ch. 10

Shallow Structures 1
Faults and kinematic criteria for determining the direction and sense of shear in the brittle deformation regime. HF Ch 9 and 10.
Extensional tectonics, normal faults, domino-type and listric normal fault systems, accommodation in the deep crust, geometry of symmetric vs. asymmetric crustal extension, syn-tectonic sedimentation.
Required literature: HF Ch. 18.

Shallow Structures 2
Thrust tectonics, thrust faults and thrust systems, concept of 2D restoration via balancing techniques. Strike-slip faults, key geometric characteristics, pull-aparts, and extensional bends.
Required literature: HF Ch. 17, and Ch. 19.

Deep Structures 1
Folds and fold mechanisms (flexural slip folding, flexural folding), development of uniform folds through shear or through homogeneous flattening, axial plane foliations, use of small-scale geometry for reconstructing large-scale structures.
Required literature: HF Ch. 12.

Deep Structures 2
Foliation development, morphology of different types of foliations: slaty cleavage, spaced pressure solution cleavage, crenulation cleavage, differentiated layering, schistosity. Concepts of multiple folding and fold interference.
Required literature: HF Ch. 13 and Ch. 14.

Deep Structures 3
Shear zones, basic features of shear zone geometry, introduction to kinematic interpretation.
Required literature: HF Ch. 15 and Ch. 16.

Deformation and Metamorphism in the Crust (Introduction to Tectonics) 1
Orogens: properties of orogens, characteristic features of orogens formed by subduction. Wilson cycle, formation and structure of ophiolite sequences.

Metamorphic Concepts 1
The nature of metamorphism; recap of the distinction between igneous, sedimentary, and metamorphic rocks; depth-temperature conditions of metamorphism; definition of metamorphic settings including impact, contact, dynamic, burial, orogenic, and oceanic.
Introduction to regional metamorphic terrains; metamorphic assemblages, metamorphic zones, isograds, metamorphic field gradient across zones; concluding with the concept of metamorphic facies.
Required literature: Klein & Philpotts, Chapter 2, Chapter 3, and Sections 5.8, 15.1, and 15.3.

Metamorphic Concepts 2
Equilibrium assemblages, the Phase rule with application to simple metamorphic rocks and metamorphic terrains. Compositional phase diagrams, application to model terrane. Using diagrams to work out reactions based on the model terrane. The ACF diagram for meta-basalts and applications to metamorphic facies.
Required literature: Klein & Philpotts Sections 8.1 to 8.8 (including box 8.3 p206) sections 15.2, 15.3, and 15.6.

INTERMISSION – CHRISTMAS BREAK
 

Metamorphic textures

The structure (and microstructure) of metamorphic rocks (slates, schists and gneiss). Identifying index minerals in photomicrographs/through optical petrography. Nucleation and growth of metamorphic minerals. Processes of recrystallization and phase transformation. The role of fluids in metamorphic reactions and ionic exchange reactions. Using textures to determine the relative timing of mineral growth and deformation. Textures produced by dynamic metamorphism and shock metamorphism.
Background literature: Lecture notes from Brightspace, Klein & Philpotts Sections 15.4, 15.5 and 15.8, and HF Section 21.4.
 

Metamorphic terranes

Introduction to real examples, pelites; AKF diagram. Metamorphic zones NE Scotland. Typical field gradients and the relation between types of field gradient and tectonic environment. Barrovian, Buchan/Pyrenean and Sanbagawan/Blueschist gradients. Paired metamorphic belts in relation to subduction zones and island arcs.
Required literature: Klein & Philpotts sections 15.6.3, 15.6.4 and 15.6.5.

Deformation and Metamorphism in the Crust
PT environments in the Earth. Steady-state geotherms leading to conclusion that metamorphism is associated with crustal deformation and magmatism. How are PT conditions in the crust changed? Prograde, peak and retrograde metamorphism. Example of PT path produced by subduction and exhumation of oceanic crust. When and why does metamorphism occur? Kinetics of reactions and importance of dehydration reactions in prograde metamorphism. Relationship between PT paths and metamorphic field gradient. Example of typical microstructure (foliation/porphyroblast relations) produced by this metamorphic history.
Required literature: Klein & Philpotts Sections 2.8, 8.10 and 15.10.
 

Deformatie en metamorfose in de korst: orogens

Example of an orogen: the structure of the Alps. Characterizing deformation and metamorphism and their time relations, reconstruction of the orogenic cycle from rifting and ocean formation to subduction (HP metamorphism) and subsequent collision (regional metamorphism),
Required literature: Klein & Philpotts Sections 2.8 and 15.10.
 

Practicals

Practical 1 – Structural Concepts
Exercise with ductile strain, concept of displacement field.

Practical 2 – Structural Concepts
Analysis of stress on a plane using Mohr circle construction, applying a failure criterion

Practical 3 – Structural Concepts
Understanding stress and strength with application to earthquakes.

Practical 4 – Extensional Structures
Reconstruction of a listric normal fault. Depth to detachment calculation, interaction between tectonics and sedimentation.

Practical 5 – Thrust Structures
Restoration of a simple thrust structure through line-length balancing.

 

Practical 6 to 9 – Fold and Thrust Belt Structure, evolution and quantification of shortening
This part of the practical sessions involves a well-documented profile through a fold and thrust belt namely the ECORS profile through the Southern Pyrenees. The exercise consists of four consecutive practical sessions, followed by writing of a short report. The requirements for this report will be explained during the practicals. This exercise, which is done in pairs, also serves as preparation for the second-year fieldwork. The exercise involves (I) an initial qualitative interpretation of surface geology supplemented with seismic and borehole data (2 practical sessions), followed by (II) a restoration of a portion of the profile and the estimation of the total accumulated minimum shortening in the South Pyrenees (also 2 practical sessions), after which (III) a concise report is written summarizing the results obtained, which is then reviewed, assessed, and returned with feedback.

Week 50: Analogue Modeling: In this part of the practical session, the formation of a thrust structure over time will be studied using a simple analogue model with the goal of better understanding the geometry of this structure and its dependence on mechanical boundary conditions. Outcome of the experiment has to be integrated in the ECORS report.

Practical 10 and 11 – Metamorphic Concepts
Metamorphic minerals and rocks. Rocks and minerals as chemical and thermodynamic systems. Identifying metamorphic minerals and their significance. Identifying and describing metamorphic rocks and their tectonic significance. Model chemical systems and compositional phase diagrams (ASH system) and the KFASH system. Example of contact metamorphic zones.
Required literature: Klein & Philpotts, Chapter 2, Chapter 3, Chapter 7, and Chapter 14.

Practical 12 to 15 – Metamorphic Concepts/Deep Crust
A case study of metamorphic rocks in an orogenic belt. Identification of metamorphic minerals and rocks in hand specimen. Using PT diagrams and compositional diagrams to estimate PT conditions and type of metamorphic field gradient.
A short report is prepared by groups of two students, describing the main results and interpretation of the geological and plate tectonic history of a regional metamorphic belt. The report is a requirement for the completion of the practical part of the course. The report is graded as pass or fail and does not contribute to the final grade of the course.
Required literature: Klein & Philpotts, Chapter 2, Chapter 3, Chapter 7, and Chapter 14.