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  Geodynamics and Geochemistry at the Institute of Earth Sciences

Geodynamics

Geodynamics is a subfield of geophysics dealing with dynamics of the Earth. Experts in geodynamics commonly use data from geodetic GPS, InSAR, and seismology, along with numerical models, to study the evolution of the Earth's lithosphere, mantle and core.
Work performed by geodynamicists may include:

Tectonics

Tectonics defines the scientific study of the deformation of the rocks that make up the Earth's crust and the forces that produce such deformation. It deals with the folding and faulting associated with mountain building; the large-scale, gradual, upward and downward movements of the crust; and sudden horizontal displacements along faults. Other phenomena studied include igneous processes and metamorphism. The chief working principle of tectonics is the concept of plate tectonics.

Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth (or other planets) and particularly with the forces and movements that have operated in a region to create these structures.

Tectonics is concerned with the orogenies and tectonic development of cratons and tectonic terranes as well as the earthquake and volcanic belts which directly affect much of the global population. Tectonic studies are also important for understanding erosion patterns in geomorphology and as guides for the economic geologist searching for petroleum and metallic ores.

There are a number of subordinate and related fields. A subfield of tectonics that deals with tectonic phenomena in the geologically recent period is called neotectonics. Tectonics is closely related to structural geology. The difference between the fields is a matter of scale: structural geologists are generally concerned with finer-scale rock deformation, while those studying tectonics are more concerned with the broader features. Tectonophysics is the study of the physics behind the tectonic processes that geologists observe.

Tectonic studies have application to lunar and planetary studies, whether or not those bodies have active tectonic plate systems.

Since the 1960s, plate tectonics has become by far the dominant theory to explain the origin and forces responsible for the tectonic features of the continents and ocean basins.

Plate tectonics is a theory which describes the large scale motions of Earth's lithosphere. The theory builds on the older concepts of continental drift, developed during the first decades of the 20th century by Alfred Wegener, and seafloor spreading, developed in the 1960s.

Structural Geology

Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation (strain) in the rocks, and ultimately, to understand the stress field that resulted in the observed strain and geometries. This understanding of the dynamics of the stress field can be linked to important events in the regional geologic past; a common goal is to understand the structural evolution of a particular area with respect to regionally widespread patterns of rock deformation (e.g., mountain building, rifting) due to plate tectonics.

The study of geologic structures has been of prime importance in economic geology, both petroleum geology and mining geology. Folded and faulted rock strata commonly form traps for the accumulation and concentration of fluids such as petroleum and natural gas. Faulted and structurally complex areas are notable as permeable zones for hydrothermal fluids and the resulting concentration areas for base and precious metal ore deposits. Veins of minerals containing various metals commonly occupy faults and fractures in structurally complex areas. These structurally fractured and faulted zones often occur in association with intrusive igneous rocks. They often also occur around geologic reef complexes and collapse features such as ancient sinkholes. Deposits of gold, silver, copper, lead, zinc, and other metals, are commonly located in structurally complex areas.

Structural geology is a critical part of engineering geology, which is concerned with the physical and mechanical properties of natural rocks. Structural fabrics and defects such as faults, folds, foliations and joints are internal weaknesses of rocks which may affect the stability of human engineered structures such as dams, road cuts, open pit mines and underground mines or road tunnels.

Geotechnical risk, including earthquake risk can only be investigated by inspecting a combination of structural geology and geomorphology. In addition areas of karst landscapes which are underlain by underground caverns and potential sinkholes or collapse features are of importance for these scientists. In addition, areas of steep slopes are potential collapse or landslide hazards.

Environmental geologists and hydrogeologists or hydrologists need to understand structural geology because structures are sites of groundwater flow and penetration, which may affect, for instance, seepage of toxic substances from waste dumps, or seepage of salty water into aquifers.

Plate tectonics is structural geology on a large scale, usually referring to the structural effects of plate collisions and other plate tectonic features.

Geochemistry

The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and their interaction with the hydrosphere and the atmosphere.

The most important fields of geochemistry are:

  1. Isotope geochemistry: Determination of the relative and absolute concentrations of the elements and their isotopes in the earth and on earth's surface. Isotope geochemistry is based on the fact that the isotopic compositions of various chemical elements may reveal information about the age, history, and origin of terrestrial and extraterrestrial materials. Isotopes of an element share the same chemical properties but have slightly different nuclear makeups and therefore different masses. Some naturally occurring isotopes are radioactive and decay at known rates to form daughter isotopes of another element; for example, radioactive uranium isotopes decay to stable isotopes of lead. Radioactive decay is the basis of geochronology, or age determination: the age of a sample can be found by measuring its content of the daughter isotope. Both radioactive decay and the processes that enrich or deplete materials in certain isotopes cause different parts of the Earth and solar system to have different, characteristic isotopic compositions for some elements. These differences serve as fingerprints for tracing the origins of, and characterizing the interactions between, various geochemical reservoirs.
  2. Examination of the distribution and movements of elements in different parts of the earth (crust, mantle, hydrosphere etc.) and in minerals with the goal to determine the underlying system of distribution and movement.
  3. Cosmochemistry: Analysis of the distribution of elements and their isotopes in the cosmos. Cosmochemistry deals with nonearthly materials. Typically, cosmochemists use the same kinds of analytical and theoretical approaches as other geochemists but apply them to problems involving the origin and history of meteorites, the formation of the solar system, the chemical processes on other planets, and the ultimate origin of the elements themselves in stars.
  4. Biogeochemistry: Field of study focusing on the effect of life on the chemistry of the earth. The field of biogeochemistry involves scientific study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the hydrosphere, the pedosphere, the atmosphere, and the lithosphere), and the cycles of matter and energy that transport the Earth's chemical components in time and space. The field focuses on chemical cycles which are either driven by or have an impact on biological activity. Particular emphasis is placed on the study of carbon, nitrogen, and phosphorus cycles.
  5. Organic geochemistry: A study of the role of processes and compounds that are derived from living or once-living organisms. Organic geochemistry deals with carbon-containing compounds, largely those produced by living organisms. These are widely dispersed in the outer part of the Earth—in the oceans, the atmosphere, soil, and sedimentary rocks. Organic geochemistry is important for understanding many of the chemical cycles that occur on Earth because biology often plays a major role. Organic geochemists are also active in investigating such areas as the origin of life, the formation of some types of ore deposits that may be biologically mediated, and the origin of coal, petroleum, and natural gas.
  6. Regional, environmental and exploration geochemistry: Applications to environmental, hydrological and mineral exploration studies.

In recent years there has been widespread application of geochemical techniques to problems in paleoclimatology and paleoceanography. In this approach, ocean sediments, sedimentary rocks on land, ice cores, and other continuous records of the Earth's history are analyzed for fossil chemical evidence of past climates or seawater composition. As in most areas of geochemistry, precise and accurate analytical methods for determining the isotopic and elemental composition of the samples are critical.

Geodynamics and Geochemistry at the Institute of Earth Sciences

At the Department for Earth Sciences, this research area is characterised by a broad assembly of topics within what is often called „hard rock geology“. It includes research of geodynamic processes, tectonics, structural geology, petrology, geochemistry and mineralogy. Thematically three regions can be discerned:

Orogenic processes:

This research field networks research in structural geology, tectonics, geochronology and petrology. This field was successively strengthened over the last 20 years and is now the strongest research area within the general key area of “geodynamics and geochemistry”. The combination of the tools of structural geology, petrology, geochemistry and geochronology has proved very successful. One of the major subjects in this area is the research of high pressure metamorphic rocks and their petrological overprinting relationships as well as the exhumation processes of such rocks. Several research projects in Argentina, Egypt, Kenya, Tanzania, Greece and Alaska are currently being conducted within this area. Special successes were the new subdivision of the East African Orogen in Tanzania as well as the recognition of UHP metamorphism in the Rhodopes (as documented by the discovery of diamond inclusions in garnets from garnet micaschists from this region). In future, this area will focus more on the Alps and their extensions towards the south and east (Carpathians, Hellenides).

Geodynamic processes and neotectonics

Study of the relationship between geodynamic processes in the crust and surface processes has gained increasing importance in the last years in the Earth sciences. In particular the ages of activity of fault zones and their influence on surface tectonic processes is being studied in our department. Also, we study the uplift of crustal blocks, the formation of topography and the development of morphology and landforms including the drainage networks. In this field the combination of low temperature geochronolgical methods, structural geology and stratigraphy has proved extremely useful in connection with numerical simulation. Several research projects in the Alps, the Himalaya are currently being conducted within this area. For example the ESF funded Topo-Alps project that operates in close connection with colleagues in Innsbruck, Hannover and the ETH Z├╝rich. Several interdisciplinary research projects focus on the on the connection of fault activity to hydrogeological processes.
http://www.topo-europe.eu/

Mineralogy and Petrology

Several research projects in our department study mineralogical-crystallographic processes as well as petrological subjects. In the field of mineralogy, our research focuses on the description of new minerals and the refinement of the crystal structure of known minerals using X-ray methods. For example, there are projects that work on the genesis and origin of gemstones (in particular corundum) using trace element and spectroscopic methods. This project is being conducted within the ASEA-UNINET program together with colleagues for Germany, Thailand, and Vietnam. Another project deals with the importance of H2O in water-absent minerals for metasomatic processes in the mantle. The classification and development of the „IMA Amphibole Nomenclatur and Classification“ is being conducted since many years in our department in cooperation with IMA. In the field of economic geology, the genesis and origin of platinum group minerals is being studied in cooperation with colleagues from Argentinia, Austria, Hungary. Several mineralogically oriented research projects operate in cooperation with partners from industry (e.g. fireproof industry, RHI, Nanotechnology Centre Weiz, Leichtmetallkompetenzzentrum Ranshofen, Swarovski) and are a fix point in this area for many years already.

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