Learning Outcomes:
On completion of this module, students should be able to:
1) Describe and identify some common rock-forming and hydrothermal minerals and rocks in hand specimen and using the petrological microscope.
2) Demonstrate in short written answers a knowledge of mineralogy, mineral chemistry, phase diagrams, textures and rock structures and how they can be used to determine the processes and environments through which igneous, sedimentary, metamorphic and hydrothermal rocks formed.
Indicative Module Content:
LECTURES
Week 1: Silicate minerals
Silicate composition of crust and mantle. The SiO4 tetrahedron, silicate polymerization and silicate classification, with examples of each class. Goldschmidt's rules, chemical substitution and solid solution.
Week 2: Crystals, minerals and polarised light
The nature of ordinary and plane polarized light. Optical properties of minerals under the petrological microscope in plane polarized light and between crossed polars. The calcite rhomb experiment. Anisotropic and isotropic minerals.
Week 3: Mineral stability and phase diagrams
Controls on mineral stability and its depiction on phase diagrams. Crystal-liquid binary diagrams (anorthite-diopside and plagioclase). Eutectic points. The Lever Rule in binary diagrams. The alkali feldspar solvus diagram and perthite textures.
Week 4: Igneous rocks
Crystallization from magmas in volcanic and intrusive environments. Controls on element partitioning, fractional crystallization, sequence of crystal growth and Bowen’s reaction series. Plate tectonics and the formation of igneous rocks. Concentration of rare metals in magmas.
Week 5: NO LECTURE.
Week 6: Siliciclastic Sediments I
Clastic Sediments & Sedimentary rocks: Grain Size and Texture. The origin of clastic sediments through weathering/erosion, the classification and description of clastic sediments, particle size characteristics (size, shape and sorting) and textual maturity and their relationship with transport processes/depositional environment and reservoir quality.
Week 7: Siliciclastic Sediments II
Clastic Sediments & Sedimentary rocks: Sandstone Composition. Common components of sandstones under thin section. QFL classification scheme. Diagenetic changes after deposition (authigenic cements, dissolution and compaction). Secondary porosity. Controls on sandstone composition and provenance analysis.
Week 8: Carbonate minerals and grains
Main carbonate minerals – aragonite, calcite and dolomite. Optical properties. Precipitation of carbonate from seawater. Modern carbonate producing environments. Skeletal and non-skeletal grains. Ooids, peloids, aggregate grains and intraclasts. Carbonate mud. Classification of carbonate sediment and rocks.
Week 9: Carbonate environments past and present
Reefs and other carbonate buildups. Reef systems through time. Use as past sea level indicators. Carbonate sands. Intertidal and supratidal limestones. Pelagic limestone – chalk and oozes. Types of carbonate platform.
Week 10: Metamorphism and pelites
Solid state recrystallization in different temperature and confining pressure environments and implications for the mineralogy and textures of metamorphic rocks; pelite metamorphic minerals; polymorphism and the Al2SiO5 polymorphs; metamorphic facies.
Week 11: Metamorphism and water
Hydration and dehydration reactions in rocks. Loss of structurally bound water from pelites with increasing temperature. Addition of water to mafic igneous rocks. Serpentinisation and its significance in hydrogen generation. Skarns as reaction products of carbonate and silicate rocks with hydrothermal fluid.
Week 12: Hydrothermal fluids and minerals
Sources of hydrothermal fluids, including the link between metamorphism and hydrothermal fluid. Reactions between hydrothermal fluids and rocks. Why hydrothermal minerals crystallize. Economic importance and brief introduction to Irish and global ore deposits.
ONLINE EXERCISES AND PRACTICAL PREPARATION
Various materials will be available on Brightspace at the start of each week. Some provide information as preparation for practicals, in the form of videos, presentations or text documents. Others consist of online exercises, with self-assessment quizzes, to deepen your understanding of topics recently introduced in lectures.
Week 1
Practical preparation: Introduction to description of mineral hand specimen properties (mp4 video).
Week 2
Exercise: Information and self-assessment related to the Periodic Table – elements, chemical symbols, atoms, ions, ionic charge and radius, co-ordination numbers, chemical bonds and chemical formulae.
Practical preparation: The Motic and Optika petrological microscopes: their parts and functions. (mp4 videos)
Week 3
Exercise: Information and self-assessment on silicate polymerization and atomic structures; classification of silicate minerals; the behaviour of aluminium in silicate minerals; element substitution, solid solution chemistry and its graphical representation.
Practical preparation: How to use the virtual microscope for revision (mp4 video)
Week 4
Exercise: Information and self-assessment on: plotting, calculations and interpretations related to phase diagrams, including binary crystal-liquid (anorthite-diopside, plagioclase) and solvus (alkali feldspar) examples.
Practical preparation: Construction of hand specimen and thin section mineral identification keys for use in the mid-trimester exam.
Week 5
Practical preparation: Completion of hand specimen and thin section mineral identification keys for use in the mid-trimester exam.
Week 6
Exercise: Sediments & Sedimentary Rocks. Introduction to sediments and sedimentary rocks, their compositional variety, thicknesses of surficial sediments across the globe, the sedimentary bedrock of Ireland and the commercial importance of sediments and sedimentary rocks.
Week 7
Exercise: Clastic Sedimentary Rocks in Thin Section. The common components of sandstones under thin section and their description. Examination of a variety of siliciclastic rocks using the Virtual Microscope website. The exercise will be self-assessed and will prepare you for the following practical.
Week 8
Practical preparation: Information on limestone components and limestone classification.
Exercise: Limestone classification using field photographs and microscope images.
Week 9
Exercise: The ‘dolomite problem’. Different mechanisms for the formation of dolomite and application to a series of examples.
Week 10:
Exercise: Use of phase diagrams to show pressure - temperature relationships between polymorphs (SiO2, Al2SiO5); relating phase diagrams to the mineralogy and texture of metamorphic rocks.
Week 11:
Exercise: Exploration of fluid-rock reactions in metamorphism and their economic implications.
Week 12:
Exercise: Expand mineral hand specimen and thin section identification keys for use in the end of trimester exam.
PRACTICAL CLASSES
Practical classes will be 3 hours long. You will be provided with a practical notebook and various small items of equipment such as a hand lens, simple mineral testing equipment and a stick of glue to fix practical handouts in your notebook. Each week you will also be provided with mineral and/or rock hand specimens, thin sections and a microscope. Apart from the notebook, all of this is on loan to you and must not be removed from the lab. At the end of most practical classes, you should hand up your practical notebook so that you can be given written feedback on your work.
Week 1: Description of common igneous minerals in hand specimen; introduction to examples of igneous rocks in hand specimen and consideration of why minerals vary in appearance between typical rocks and the mineral hand specimens.
Week 2: Introduction to the petrological (polarizing) microscope; description of the properties of minerals in granite (quartz, plagioclase, microcline, orthoclase, biotite, muscovite) and aplite (garnet) in thin section. Description of interference colours and the Michel Levy chart. Twinning in hand specimens (e.g. gypsum) and in thin section (feldspars). Comparison of thin section and hand specimen properties of granite minerals.
Week 3: Description of olivine, augite, magnetite and hornblende in mineral hand specimens and in thin sections of mafic igneous rocks, and how to distinguish between them. Extinction angles of mafic minerals and mineral identification. The use of igneous minerals and textures in understanding the origin of magmas and crystallization of igneous rocks.
Week 4: Description of a variety of igneous rocks in hand specimen, and interpretation of their textures and mineralogy, including their conditions of crystallization and possible plate tectonic setting. Revision of igneous rock thin sections.
Week 5 – NO PRACTICAL CLASS
Week 6: Clastic Sedimentary rocks. Description of clastic rocks in hand specimen and thin section. Look at a range of clastics in hand specimen, evaluation of common sedimentary structures and description of thin section of granite-derived sediment.
Week 7: Sandstones. Description of several thin sections of sandstones to determine their QFL composition, likely depositional environment and tectonic settling.
Week 8: Description of calcite, aragonite and dolomite in hand specimen and of calcite and dolomite in carbonate sedimentary rock. Distinguishing skeletal and non-skeletal limestone components and application of Folk and Dungham limestone classification schemes.
Week 9: Carbonates: Reconstructing limestone depositional environments and environmental change by combining information from sedimentary structures, hand specimens and thin-sections.
Week 10: Metamorphic rocks 1: Metasedimentary rocks. Description of andalusite, kyanite, sillimanite, staurolite, chlorite and garnet in hand specimen and thin section. The use of metamorphic minerals and their textures in understanding metamorphic history - regional and contact metamorphism.
Week 11: Metamorphic rocks 2: Metabasite, metaperidotite, metacarbonate and metagranitic rocks. Epidote and actinolite in hand specimen and in metabasite thin sections. Garnet metagabbro and serpentinisation of olivine in thin section. Marble in hand specimen and thin section. Granitic gneiss and skarn in hand specimen.
Week 12: Hydrothermal minerals. Simple atomic structure and high symmetry of many hydrothermal minerals. Hand specimen properties of streak, specific gravity and HCl reaction. Description of common hydrothermal minerals in hand specimen and consideration of their possible economic significance. Brief examination of hydrothermal rocks of economic interest.