Learning objectives
The main objective of this course is to provide a basic understanding of the magma generation in the different geodynamic environments through time and the relations between magmatic/metamorphic processes and plate tectonics
Prerequisites
none
Course unit content
APPLICATION OF TRACE ELEMENT AND ISOTOPE GEOCHEMISTRY TO PETROLOGY
PETRO-TECTONIC ASSOCIATIONS:
Mid-ocean ridge magmatism
Mantle plumes and oceanic islands
Mantle plumes and basaltic plateaux
Arc magmatism
Collisional granitoids
Continental rift magmatism
CASE STUDIES BASED ON FIELD OCCURRENCES IN THE ALPS AND NORTHERN APENNINE
Full programme
INTRODUCTION
-Mantle composition and heterogeneity
-Causes of melting and origin of magmas
1-GEOCHEMISTRY OF TRACE ELEMENTS AND RADIOGENIC ISOTOPES: PETROLOGICAL APPLICATIONS
-Principles of geochemistry of trace elements: partition coefficients, compatible and incompatible elements, representation of trace elements (normalizations)
-Geochemical models of crystallization, mixing, AFC, partial melting
-Radiogenic isotopes as tracers of petrogenetic processes: Rb / Sr, Sm / Nd, Lu / Hf, Re / Os, U-Pb-Th systems
-Model ages, internal isochrons, closure temperature
-Carbon in the mantle
2-GEOCHEMICAL CHARACTERISTICS OF MAGMAS AND PETROGENETIC PROCESSES AT DIFFERENT GEODYNAMIC SETTINGS:
DIVERGENT PLATE BOUNDARIES AND MID-OCEAN RIDGES
-structure, composition and lithologies in the modern and fossil oceanic lithosphere
- oceanic lithosphere at fast, slow and ultra-slow spreading-ridges; oceanic core complexes
-mineralogy and geochemistry of MORB and of the lower oceanic crust
-petrogenesis of MORBs, segregation and ascent: from single melt increments to aggregated melts
- geochemical and isotopic heterogeneity in the MORB source
- plume-ridge interactions
- hydrothermal alteration of the oceanic crust
- serpentinization processes and their petrogenetic relevance
MAGMATISM AT CONVERGENT PLATE BOUNDARIES
-distribution, type and structure of magmatic arcs
- magmatic series in intra-oceanic arcs: petrographic, mineralogical and geochemical characters (FAB, boninites, adakites, arc tholeiites, shoshonites, leucitites..)
-sources of magmas and their evolution
-melting/ dehydration of subducted lithosphere
-melting of the mantle wedge
-release of fluids / melts from the slab and transfer of components from the slab to the mantle wedge: experimental studies and HP-UHP metamorphic rocks as natural laboratories
-role of serpentinites
-new petrogenetic models involving diapiric ascent and melting of melanges from the subducted slab
-isotopic tracers of arc processes (Sr, Nd, Pb, B, Be)
-continental arcs: magmatic series and the role of the continental lithosphere; examples from the Andes and the Cascade Range
-origin of granitic magmas: processes of differentiation, anatexis (fluid-present and fluid-absent melting), hybridization
OCEANIC INTRAPLATE MAGMATISM AND MANTLE PLUMES
-Global distribution and tomographic images of hotspots and of subducted plates
-type of OIB magmas
-isotopic variations of Sr, Nd, Hf, Pb, Os and mantle reservoirs (“geochemical geodynamics and the mantle zoo”)
-relationships between mantle plumes and crustal recycling processes
-nature and origin of components in the sources of OIB magmas
-role of pyroxenites
-Sobolev model and Di-CaTsch-Fo-Qtz system
-structure and melting in a mantle plume
-example of Hawaiian magmatism
CONTINENTAL INTRAPLATE MAGMATISM
-basaltic plateaux
-composition and origin of carbonatitic magmas
-ultrapotassic magmas
3- CASE STUDIES:
-ophiolites of the Internal Ligurian Units (N Apennine) as example of oceanic lithosphere formed at a slow/ultra-slow spreading ridge
-ophiolites of the External Ligurian Units (N Apennine) as example of oceanic lithosphere originated at an ocean-continent transition zone
- continental rifting and oceanization processes
- post-Varisic magmatism and the crustal section of the Ivrea area (Southern Alps)
- Notes on the architecture of the Alpine and Apennine chain and the main magmatic and metamorphic events
Bibliography
Slides, scientific articles and links to web sites will be available to download by the students on the web platform “Elly”. Materials could be updated during the Course.
TEXTBOOKS
- John D. Winter (2010), Principles of igneous and metamorphic petrology, Ed. Prentice Hall
-H. Rollinson (1998) - Using geochemical data (cap. 4 e 6)
- M.G. Best and E.H. Christiansen, Igneous Petrology (Blackwell Science)
- A. Philpotts and J. Ague, Principles of Igneous and Metamorphic Petrology (Cambridge University Press)
Teaching methods
Slides provided during classes will be weekly available to download on Elly platform. To download the slides, students need to be registered on-line to the Course. Please note that the slides are not a substitute for lessons or of the Textbooks but are considered part of the accompanying instructional materials. Students should frequently control instructional materials and other information provided by the Teacher on the Elly web site.
-1. Lectures
- 2. Optical microscope observations * of thin sections related to specific case studies treated during the course (magmatic and mantle rocks from ophiolitic sequences; mantle xenoliths affected by metasomatic processes)
- 3. Field excursions*: 5 days of fieldwork on selected and well known outcrops from the N Apennine and W Alps which will provide examples of oceanic lithosphere, mantle heterogeneity, continental lower crust and orogenic metamorphism
* if 2-3 could not be realized due to Covid-19 emergency, they will be replaced by images and detailed field guides
Assessment methods and criteria
The method of verifying learning may be different based on the progress of the Covid 19 emergency. Therefore two possible methods are envisaged. 1) IF POSSIBLE TO CONDUCT EXAMINATIONS IN PRESENCE for all students; 2) IT IS NOT POSSIBLE TO CONDUCT EXAMINATIONS IN PRESENCE BUT ONLY IN REMOTE MODE (TELEMATICS).
In both cases, the assessment of learning will take place through a single final test via oral exam
including:
- discussion of a scientific article from the recent literature on a topic of the course chosen by the student
- 1question concerning trace element and radiogenic isotope geochemistry
-2 questions about magmatic associations and related geodyamic settings
- 1 question about case studies from Alps and Apennines
Other information
Information on the aim and content of the course (see above and below) are associated with the relative "Dublin Indicators" (DI) that characterize their purposes. Dublin Indicators: - Knowledge and understanding; - Applying knowledge and understanding; - Making judgements; - Communication skills; - Learning skills.
