Petrology

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Dark alum slate , near Brétignolles , Vendée department , France

The petrology , even Gemology , is the study of the origin, characteristics and use of the rocks . The term is derived from the Greek word πέτρος pétros , Latin Petrus , which can be translated as ' stone ' or ' rock '. It is a sub-area of geosciences and represents the transition area between two further sub-areas: mineralogy , which deals with the constituents of rocks ( minerals ), and geology , which places rocks in larger spatial and temporal contexts.

research object

Petrology is divided into a descriptive part, petrography , and a genetic part, petrology in the narrower sense. The former deals with the structure of the rocks, which consists of their structure and texture . The structure describes the individual components (grains, crystals , pores in the case of sedimentary rocks ) of the rocks in terms of their size, shape and color as well as the statistical distribution of these properties over the entirety of all components. The texture, on the other hand, describes the spatial arrangement of these components in the entire rock with regard to crystallographic preferred orientations. From these properties, petrographers deduce the suitability of rocks as a material , both in the form of blocks and in broken form. Petrology in the narrower sense, on the other hand, uses petrographic, structural geological and geochemical knowledge to enable petrologists to reconstruct the physical and chemical formation conditions of a rock.

Investigation methods

The basis of petrological work is field work with a magnifying glass and geological compass . Later, the rocks are examined in the laboratory using mineralogical and geochemical methods such as X-ray diffraction or microprobe analysis. The most important dedicated petrological method is polarization microscopy , with the help of which the structure of the rocks is examined. Here z. T. accessories such as the universal turntable used. One method for the petrological interpretation of geochemical data is geothermal barometry , which makes statements about the pressure and temperature at the time a rock was formed or metamorphosed . Hypotheses about the formation and development ( diagenesis , metamorphosis, metasomatosis , weathering , hydrothermal overprinting) of a rock are checked by simulating geological and mineralogical processes in laboratory experiments. Here z. For example, artificial magmas are generated and their solidification is observed, or rocks are brought into contact with aggressive solutions that also occur in nature. The modeling of magmatic, metamorphic and sedimentary processes with the help of computers is used to interpret experimentally obtained data, but also as an independent approach .

Sub-disciplines

  • A breakdown of petrology according to the object of investigation enables a distinction to be made between igneous , sedimentary and metamorphic petrology - corresponding to the three main rock classes, namely igneous, sedimentary and metamorphic rocks.
  • A distinction according to the investigation methods leads to experimental, analytical and theoretical petrology.
  • Areas that deal with the economic use of rocks, e.g. B. as a decorative stone, is called applied petrology.
  • The transition area to geophysics , which deals in particular with the behavior of seismic waves in rocks, is called petrophysics.

Education

Petrological course content is taught in the "Geosciences" course.

Fields of work

Petrologists are in engineering offices in the ground investigation , in mining companies in prospecting , exploration and ongoing operations (e.g. as operations manager of a quarry ), in building materials dealers in the sale of decorative stones and stone, in the public service at geological state offices and in the Federal Institute for Geosciences and Raw Materials as well as active in the scientific field at universities and non-university research institutions.

literature

  • Gregor Markl: Minerals and Rocks . 1st edition. Spektrum Akademischer Verlag, Heidelberg 2004, ISBN 978-3-8274-1495-3 .
  • Ludwig Pfeiffer, Manfred short, Gerhard Mathé: Introduction to petrology . Akademie Verlag, Berlin 1981, ISBN 978-3-432-91931-7 .
  • Martin Okrusch , Siegfried Matthes : Mineralogy. An introduction to special mineralogy, petrology and geology. (1st edition, still without Martin Okrusch, 1983) 8th edition. Springer-Verlag, Berlin 2009, ISBN 978-3-540-78200-1 .
  • Roland Vinx: Rock determination in the field . Spectrum Academic Publishing House, Heidelberg 2005, ISBN 3-8274-1513-6 .
  • Journal of Petrology
  • Bernhard Fritscher : volcanoes and blast furnaces. On the role of metallurgical experience in the development of experimental petrology . In: Technikgeschichte, Vol. 60 (1993), H. 1, pp. 27-43

Web links

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