2018/2019

2019/2020

DM270

GEO/08 (GEOCHEMISTRY AND VOLCANOLOGY)

DEPARTMENT OF EARTH AND ENVIRONMENTAL SCIENCES

GEOLOGICAL SCIENCES

PERCORSO COMUNE

2°

2nd semester (02/03/2020 - 12/06/2020)

6

48 lesson hours

Italian

ORAL TEST

SACCHI ELISA (titolare) - 6 ECTS

The course requires basic notions of Mathematics, and Chemistry, as provided in the Degree courses of Geological Sciences, and namely: atomic particles and structure, isotopes, periodic table of the elements, electronic configuration, valence, metallic and non-metallic properties, atomic radius, ionization potential, electronegativity, ionic and covalent bonds, trends of the chemical properties across the periodic table. These notions will be reviewed at the beginning of the course.

The course provides an introduction to geochemistry and is aimed at undergraduate students who require an appropriate understanding of basic chemical principles of geological processes. The objective of the course is to familiarise students with the tools of geochemistry, that include thermodynamics, kinetics, aquatic chemistry, trace element geochemistry, and isotope geochemistry. A quantitative approach of geological processes using major and trace elements, as well as radiogenic and stable isotopes is stressed wherever possible.
Among expected learning outcomes are the capability to interpret chemical and isotopic fractionation processes, to use elements and isotopic ratios as tracers of geologic, petrogenetic and hydrogeological processes, and to reconstruct the elemental cycles in different environments.

Fundamentals of geochemistry.
Review of the main properties of the elements with regards to their position in the periodic table. The internal structure of the atoms.
Primordial and stellar nucleosyntheses. Elemental abundances in the universe and in the solar system. Meteorites. Origin and differentiation of the Earth. The Earth structure and composition. The atmosphere, the hydrosphere and the biosphere. Elemental cycles (P, inorganic and organic C, O, N and S) and their evolution during geological times.
The classification of the elements of geological interest. Major, minor and trace elements. Compatibile and incompatibile elements. Large Ion Lithophile Elements (LILE), 3d Transition elements. High Field Strength Elements (HFSE), Rare Earth Elements (REE), Platinum Group Elements (PGE). Goldschmidt’s classification of the elements.
Geochronology
Types of radioactive decay. The decay equation. Decay series. Nuclide chart.
Age dating methods The Rb-Sr system and its application to magmatic and metamorphic rocks. The evolution of Sr isotopes on the Earth and dating of sedimentary rocks. The Sm-Nd system. Sr and Nd isotopes as tracers of petrogenetic processes. The U-Th-Pb system. Geochemistry of U and Th. Conditions for secular equilibrium. U-Pb dating of zircons. Concordia and Discordia diagrams for U-Pb . The Pb-Pb system and the geochron. Age of meteorites and of the Earth The K-Ar method and its application. The Ar-Ar method. Dating with 14C.
Geochemistry of high temperature processes
Revision of thermodynamics and definition of system, phase and component. Solutions and thermodynamics of multicomponent system. Binary phase diagrams. The phase rule. Examples of systems with complete solid solution, with eutectic, with peritectic. Two phase liquids and exsolutions. Melting and crystallization at equilibrium or fractional, and the relative effects on the final rock or liquid produced. Ternary phase diagrams. Influence of P and H2O content on phase equilibria.
Genesis and chemical evolution of magmas. Behaviour of major and minor elements. Trace elements and their classification based on their geochemical behaviour. Solid-liquid partition coefficients. Factors affecting the value of partition coefficients (P, T, crystal structure and melt composition). The evolution of mantle and crust. Primitive mantle and depleted mantle.
Geochemistry of low temperature processes
Hydrochemistry: main hydrochemical parameters measured in water (temperature, conductivity, pH, Eh, alkalinity). Major cations and anions. Concentration units. Graphical representation of results and classification of water types.
Water-rock interaction processes: dissolution/precipitation (equilibrium constant, solubility and solubility product, saturation indices), oxidation/reduction (main reactions), ion exchange (main ion exchangers). Carbonate and silicate dissolution. Pyrite oxidation.
Environmental isotopes: notation and expression of the results. International standards. Stable isotopes and their fractionation. Stable isotopes of the water molecule and their application. Isotopic composition of precipitation, the meteoric water line, isotope exchange during water-rock interaction.

The course consists in lectures that include the explanation of the theoritical aspects and the development of exercises and calculations to illustrate through practical examples the application of the theory to geochemical problems.

Main textbooks:
- White W.M. 2013. Geochemistry. Wiley-Blackwell
- Gill R.C.O. 1988. Chemical fundamentals of geology. Unwin Hyman, London.
- Faure G. 1998. Principles and applications of geochemistry. Prentice Hall
- Dongarrà G., Varrica D. 2004. Geochimica e Ambiente. EdiSES
- Winter J.D. 2014. Principles of Igneous and Metamorphic Petrology. Pearson Education Limited

Suggested readings:
- Rollinson H.R. 1993. Using geochemical data: evaluation, presentation, interpretation. Longman Scientific & Technical.
- Faure G. 1986. Principles of isotope geology. 2nd edition. John Wiley & Sons, New York
- Ottonello G. 1991. Principi di geochimica. Zanichelli, Bologna.
- Cox K.G., Bell J.D., Pankhurst R.J. 1979. The interpretation of igneous rocks. Allen & Unwin, London.
- Wood B.J. & Fraser D.G. 1978. Elementary thermodynamics for geologists. Oxford University Press.
- Nordstrom D.K. & Munoz J.L. 1985. Geochemical thermodynamics. The Benjamin/Cummings Publishing Company, Inc., Menlo Park, California.
- Longinelli A. & Deganello S. 1999 Introduzione alla geochimica. Utet.
- Clark I & Fritz P. 1997 Environmental isotopes in hydrogeology. Lewis Publishers, Boca Raton

For students attending the course, two partial assessments are planned. Each consists in 4-5 open questions to check the preparation on the
course subjects. Alternatively, students can take a final oral examination where, besides the knowledge of the course subjects, their capability to
solve goechemical problems similar to those illustrated during the lectures will be tested.

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