Learning outcomes of the course unit
The ore deposits are the product of a more or less complex series of geological events that led to the formation of useful mineral substances in a certain portion of the crust. To know the processes that give rise to the various types of ore deposits is essential to suggest the exploration and exploitation of mineral resources. The role of the geologist is to find ore bodies and natural enrichments of metals, but also to describe and evaluate the characteristics of ore deposits and the geological factors that control the extraction costs of a product. The main purpose of the course is to provide a better understanding of the geochemical, petrological, structural and sedimentological features which cause the formation of different types of ore deposits. The course also aims to highlight the importance of the geologist not only in the mining exploration but also in assessing the impact that both the mining and the processing phases have on the environment.
At the end of the course the student must be able to:
- know the formation processes of the various types of ore deposits
- know how to recognize these processes on the field
- perform the geological investigations indispensable in any mining exploration project
- assess the environmental impact due to the processes of mining and extraction of metals.
Knowledge of Mineralogy, Petrography, Geochemistry, Structural Geology is required
Course contents summary
At first, the basic concepts used in the mining exploration and the field features useful for a pre-exploration phase (morphological and mineral-petrographic features of the ore bodies, structures and textures of ore and gangue minerals, alteration of country rocks) are provided. A second part describes the various types of mineralizing fluids, their source and the driving forces for their movement, solubility of metals, methods of transport and precipitation/deposition of ores, the various types of ore deposits and their forming processes (orthomagmatic deposits, magmatic-hydrothermal deposits, hydrothermal deposits, sedimentary deposits, supergenic deposits). Finally, the last part deals with mining exploration methods, mainly with geochemical exploration, briefly with metallurgical processes for extracting metals and with the impact that both the mining and the processing phases (and therefore waste) they can have on the environment. The course also includes field excursions and observation of ore minerals using reflection light microscopy
1. Basic definition and concepts used in ore geology. Morphological and mineral-petrographic features of ore bodies. Structures and textures of ore and gangue minerals. Alteration of hosting rocks. Classification of ore deposits.
2. Enrichment processes. Physical and chemical driving forces for enrichment in metals. Sources of metals. Types of fluids. Alteration of hosting rocks.
Solubility of gangue mineral and metals. Transportation of metals. Precipitation/deposition of ores.
Orthomagmatic ore deposits. Element partition between phases, partial melting, fractional crystallization, liquid immiscibility. Deposits formed by low degrees of partial melting. Deposits formed for accumulation in magma chamber. Deposits formed through separation of immiscible liquids. Deposits formed through extreme fractionation of magma. Deposits formed through incorporation of a mineral from depth.
Magmatic-hydrothermal ore deposits. Porphyry deposits. Epithermal deposits.
Hydrothermal ore deposits. Hydrothermal ore deposits with close temporal and spatial relations with magmatic activity (VMS), syn-orogenic hydrothermal deposits without relations with magmatic centers (Au orogenic deposits, IOCG), hydrothermal deposits in sedimentary basins (SEDEX, MVT, SCC, U deposits).
Sedimentary ore deposits. Sorting, transport and sedimentation processes. Debris-alluvial deposits (placers). Chemical precipitation deposits (ironstones, BIFs, Mn deposits).
Superficial or supergene ore deposits. Principles of chemical weathering. Laterite deposits (bauxite, Ni and Co, Au, PGE), calcrete-hosted deposits (U and V), supergene enrichment from primary mineralizations (Cu).
3. Geological concepts and methods in mining exploration. Geochemical exploration. Evaluation of mineral deposits. Metal extraction methods (metallurgy). Mining, extraction and the environment. Remediation strategies.
Robb L. (2010) Introduction to ore-forming processes. Blackwell Publishing, Oxford, p.373
Ridley J. (2013) Ore deposit geology. Cambridge University Press, Cambridge, p. 398
Evans A. (2009) Ore geology and industrial minerals. An introduction. Blackwell Publishing, Oxford, p.389
Pohl W.L. (2011) Economic Geology. Principles and Practice. Wiley-Blackwell, Oxford, p. 663
Jambor J.L., Blowes D.W., Ptacek C.J. (2000) Mineralogy of mine wastes and strategies for remediation. In: Waugham D.J., Wogelius R.A. – Environmental Mineralogy. EMU Notes in Mineralogy Vol. 2, pp. 255-290
De Vivo B., Barbieri M. (1991) Prospezioni geochimiche. Liguori editore (capitoli 19, 20, 21, 22)
Lectures on basic theoretical topics and field lessons aimed to the identification and recognition of the ore deposits.
The teaching material is provided personally to the student or posted on Elly after each lesson.
Assessment methods and criteria
Oral exam with verification of the theoretical knowledge learned, their application to real cases and verification of the logical-deductive skills (normally performed face-to-face or remotely with the Teams platform if necessary).
The final evaluation of the oral exam is communicated immediately at the end of the exam itself