Programme

- Introduction to petrography and rock-forming processes
Definition of a rock. Differences and relationships between petrography and petrology. Igneous, sedimentary and metamorphic rocks and the main rock-forming processes. The rock cycle and exchanges of matter and energy between the lithosphere, hydrosphere, atmosphere and biosphere. Distribution of the main rock types in Italy. Study of rocks at the microscopic, macroscopic, outcrop and planetary scales. Main petrographic and petrological investigation methods: hand-specimen observation, petrographic microscopy, electron microscopy, X-ray fluorescence spectrometry and electron microprobe analysis. Rocks and minerals as natural resources and the sustainability of their use.
- Composition and structure of the Earth
Origin of the elements and formation of the Solar System. Accretion and differentiation of the Earth; meteorites and chondrites as sources of information about the Earth’s composition. The geological time scale. Methods used to investigate the Earth’s interior: the surface geological record, xenoliths, meteorites, experimental petrology and geophysical surveys. P and S seismic waves and the main discontinuities. Subdivision of the Earth into crust, mantle, outer core and inner core. Oceanic and continental crust: structure, composition and main rock types. Mineralogical composition of the upper mantle and its variation with depth; the mantle transition zone and lower mantle. Composition and physical state of the core.
- Dynamics of the Earth
Lithostatic pressure gradient, geothermal gradient and heat flow. Sources of the Earth’s internal heat and heat transfer by conduction and convection. Lithosphere and asthenosphere. Continental drift and plate tectonics. Divergent, convergent and transform plate boundaries; formation and destruction of the lithosphere, subduction, collision and orogenesis. Relationships between Earth dynamics, the distribution of earthquakes, magmatism and rock formation.
- Nature and properties of magma
Definition of magma and distinction between magma and lava. Mantle-derived and crustal magmas. The multiphase nature of magma: silicate melt, crystals and volatile phase. Major and trace elements; expression of chemical composition in terms of oxides. Main volatile species. Compositional classification of magmas as ultrabasic, basic, intermediate and acidic. Structure of silicate melts, polymerisation and the role of polymerising and depolymerising elements. Temperature, density and viscosity and their relationships with magma composition, crystals, bubbles and volatiles. Solidus and liquidus.
- Occurrence, structure and classification of igneous rocks
Intrusive, hypabyssal, volcanic and pyroclastic rocks. Main intrusive bodies: batholiths, stocks, laccoliths, dykes, dyke swarms, sills and volcanic necks. Main types of volcanic edifices and relationships between magma composition and morphology. Structure and texture of igneous rocks: absolute and relative crystal size, degree of crystallinity, crystal shape and spatial arrangement. Phaneritic and aphanitic, equigranular and inequigranular, porphyritic, holocrystalline, hypocrystalline, hypohyaline and glassy textures. Euhedral, subhedral and anhedral crystals; panidiomorphic, hypidiomorphic and allotriomorphic textures. Felsic and mafic minerals and colour index. Modal and normative mineralogical classifications. QAPF classification of intrusive and volcanic rocks and TAS chemical classification of volcanic rocks. Silica saturation and the main igneous rock families.
- Generation, ascent and evolution of magmas
Partial melting in the mantle and crust. Mineralogical composition and stability fields of upper-mantle peridotites. Mechanisms of mantle melting: adiabatic decompression and addition of volatile components. Relationships between magma generation and geodynamic setting. Separation of melt from the source rock, buoyancy-driven ascent and storage in magma reservoirs. Primary and evolved magmas. Magmatic evolution and differentiation through fractional crystallisation, assimilation of surrounding rocks and magma mixing.
- Melting of rocks and crystallisation of magmas
Magmatic systems and the concepts of system, component, phase and degrees of freedom. The phase rule. One- and two-component systems. Relationships between solid and liquid phases, solidus and liquidus curves, and use of the lever rule. Equilibrium and fractional melting and crystallisation. Phase diagrams involving eutectics, peritectics and solid solutions. Representative mineral systems: diopside-anorthite, forsterite-silica, plagioclase, olivine and alkali feldspar systems. Interpretation of crystallisation sequences, microstructures and the compositional evolution of magmatic liquids. Relationships between partial melting, fractional crystallisation and the formation of magmatic series.
- Volcanism and eruptive products
Distribution of volcanism in different geodynamic settings. Monogenetic and polygenetic volcanoes and volcanic complexes; shield volcanoes and stratovolcanoes. Effusive and explosive eruptions and the main eruptive styles. Eruption size: intensity, magnitude and the Volcanic Explosivity Index (VEI). Lava and pyroclastic products. Juvenile and lithic pyroclasts; volcanic bombs, blocks, lapilli, ash, scoria, pumice, spatter and accretionary lapilli. Eruption columns, fallout and pyroclastic density currents. Consolidation and classification of pyroclastic rocks. Introduction to volcanic hazards, with particular reference to Italy.
- Formation and classification of sedimentary rocks
Physical and chemical weathering of rocks, erosion, transport and deposition of sediments. Lithification and the main diagenetic processes. Components of sedimentary rocks: grains, matrix and cement. Texture, grain size, grain shape, roundness, sorting, packing and fabric. Textural and compositional maturity. Grain-size classification of siliciclastic sedimentary rocks: rudites, arenites and lutites. Orthoconglomerates and paraconglomerates; conglomerates and breccias. Composition and classification of terrigenous sandstones: quartz arenites, arkoses, litharenites and greywackes. Carbonate rocks: allochemical and orthochemical components, granular and bioconstructed textures, and the Folk and Dunham classification schemes. Limestones and dolostones; early and late dolomitisation. Evaporite rocks and the sequence of the main evaporite minerals. Siliceous rocks of biogenic, chemical and diagenetic origin; cherts, radiolarites, spongolites and diatomites. Introduction to the other main families of sedimentary rocks.
- Metamorphic processes and metamorphic rocks
Definition and limits of metamorphism. Orthometamorphic, parametamorphic and polymetamorphic rocks. Main controlling factors of metamorphism: temperature, lithostatic pressure, directed stress and fluids. Recrystallisation, metamorphic reactions and index minerals. Metamorphic grade and metamorphic facies. Regional or dynamothermal metamorphism, thermal or contact metamorphism, burial metamorphism, ocean-floor metamorphism, hydrothermal metamorphism, fault-zone metamorphism and impact metamorphism. Relationships between types of metamorphism and geodynamic settings. Isotropic and anisotropic metamorphic structures and textures; foliation, lineation, cleavage, schistosity and gneissic texture; granoblastic textures. Main metamorphic rocks and metamorphic-grade sequences: slates, phyllites, schists, gneisses, hornfelses, granofelses, marbles and other rocks derived from pelitic, basaltic and carbonate protoliths.

- Practical classes
The course includes five practical classes closely integrated with the corresponding theoretical modules:
• interpretation of simple phase diagrams, carried out in the classroom;
• macroscopic and microscopic recognition and description of the main intrusive igneous rocks;
• macroscopic and microscopic recognition and description of the main volcanic rocks;
• macroscopic and microscopic recognition and description of the main sedimentary rocks;
• macroscopic and microscopic recognition and description of the main metamorphic rocks.
During the petrography practical classes, students examine hand specimens and thin sections under the petrographic microscope, focusing on mineralogical composition, structure, texture, classification and petrogenetic significance.

Prerequisiti

A basic knowledge of the main geological processes and the fundamentals of mineralogy is required, particularly with regard to the composition, structure and properties of the most common rock-forming minerals. There are no formal prerequisite courses.

Core Documentation

MINERALOGIA E PETROGRAFIA – C. Klein, A.R. Philpotts (Zanichelli)
Course material (texts, figures, and exercises) provided by the instructor

Attendance

Attendance at classroom lessons and practical laboratory classes is governed by the Academic Regulations of the Degree Programme, which specify the minimum attendance requirements and any provisions applying to particular categories of students.

Type of evaluation

Assessment takes the form of a 90-minute written examination designed to evaluate the knowledge acquired and the student’s ability to apply it to the description, classification and interpretation of rocks and the main rock-forming processes. The examination consists of five open-ended questions, each worth between 1 and 4 points, for a maximum total of 20 points, and ten closed-ended questions, each worth 1 point, for a maximum total of 10 points. Questions cover the different parts of the syllabus, with particular reference to igneous, sedimentary and metamorphic processes, and may require the interpretation of simple diagrams, phase diagrams, or compositional and textural characteristics of rocks. The open-ended questions assess the accuracy and completeness of the student’s knowledge, the ability to establish relationships between processes and products, the application of classification and interpretative criteria, the coherence of the argument and the appropriate use of scientific terminology. The closed-ended questions assess knowledge of fundamental concepts and the ability to distinguish correctly between definitions, processes, materials and classification criteria. Taken together, the questions assess competences related to the five Dublin Descriptors: knowledge and understanding of rock-forming processes; application of knowledge to rock classification and interpretation; independent judgement in selecting relevant evidence; communication skills in answering open-ended questions; and the ability to apply the acquired criteria to simple problems and cases not presented in exactly the same form during the course. The examination is passed with a minimum mark of 18/30. The final mark is calculated by adding the points awarded for the open-ended and closed-ended questions. Honours may be awarded to examinations achieving a mark of 30/30 when the open-ended answers demonstrate a comprehensive command of the course content, an outstanding ability to establish connections and formulate independent interpretations, and exceptional clarity and rigour.