Learning objectives
The aim of the course is to provide to the student the basic knowledge of Geochemistry for understanding and quantifying some geological processes of both high and low temperature. Fundaments of thermodynamics are applied to (i) the solubility af the mineral phases in aqueous solutions, (ii) the water-rock interaction and (iii) the behaviour of the trace elements during magma generation and evolution. Isotope geochemistry fundaments are applied to geochronological, petrological and climatic-environmental topics.
Course unit content
Thermodynamics: intensive and extensive properties, system, phase, component. State functions, the chemical potential, the equilibrium constant.
Low temperature systems
- Equilibria in aqueous solutions: saturation index, the solubility of carbon dioxide and the carbonate equilibria. The solubility of calcite. Dolomite and dolomitization.
- Redox processes: the redox potential, the Eh vs. pH diagrams of the water, Fe and Mn phases. The origin of the Mn-ore deposits. Eh vs. pH isoactivity diagrams of N, S and Cl specie.
- Silicate weathering: the stability of primary silicates and of weathering products (quartz, k-feldspar, muscovite, kaolinite, gibbsite)
- Rock weathering and mass balance calculations: variations of the mass of the chemical components and of the volume of the rocks. The Ki parameter as indicator of the mobility of the elements.
High temperature systems
- Partition coefficients: definition and dependence on temperature, pressure and composition. Compatible and incompatible behaviour of the elements. Fractionation processes: Rayleigh crystallization and total equilibrium crystallization. Melting processes: partial melting of the peridotite mantle. The geochemical diagrams (element vs. element, REE profiles, spiderdiagrams) applied to petrology.
Isotope geochemistry: the isotopes and the radioactive isotopes, the radioactive decay law. Dating: the K/Ar, Rb/Sr, U/Pb and the Pb methods.Stable isotopes: the fractionaton of the isotopes. The factors affecting fractionation. The applications of the stable isotopes to hydrological, palaeoclimatic and palaeoenvironmental studies.
Bibliography
Aquatic Chemistry - Stumm & Morgan
- Study and interpretation of the characteristics of natural waters - Hem
- Solutions, minerals and equilibria - Garrels and Christ
- Equilibres chimiques - Michard
- The geochemistry of natural waters - Drever
- Principles of isotopes geology - Faure
- Geochemistry, pathways and processes - Richardson and McSween
- Geochimica e ambiente - Dongarrà e Varrica
Teaching methods
Oral and practical lesson
