Petrology

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Petrology

Petrology (from the Greek πέτρος, pétros, "rock" and λόγος, lógos, "subject matter", see -logy) is the branch of geology that studies the origin, composition, distribution and structure of rocks.

Methodology

Petrology utilizes the fields of mineralogy, petrography, optical mineralogy, and chemical analysis to describe the composition and texture of rocks. Petrologists also include the principles of geochemistry and geophysics through the study of geochemical trends and cycles and the use of thermodynamic data and experiments in order to better understand the origins of rocks.

Branches

There are three branches of petrology, corresponding to the three types of rocks: igneous, metamorphic, and sedimentary, and another dealing with experimental techniques:

  • Igneous petrology focuses on the composition and texture of igneous rocks (rocks such as granite or basalt which have crystallized from molten rock or magma). Igneous rocks include volcanic and plutonic rocks.
  • Sedimentary petrology focuses on the composition and texture of sedimentary rocks (rocks such as sandstone, shale, or limestone which consist of pieces or particles derived from other rocks or biological or chemical deposits, and are usually bound together in a matrix of finer material).
  • Metamorphic petrology focuses on the composition and texture of metamorphic rocks (rocks such as slate, marble, gneiss, or schist which started out as sedimentary or igneous rocks but which have undergone chemical, mineralogical or textural changes due to extremes of pressure, temperature or both)
  • Experimental petrology employs high-pressure, high-temperature apparatus to investigate the geochemistry and phase relations of natural or synthetic materials at elevated pressures and temperatures. Experiments are particularly useful for investigating rocks of the lower crust and upper mantle that rarely survive the journey to the surface in pristine condition. They are also one of the prime sources of information about completely inaccessible rocks such as those in the Earth's lower mantle and in the mantles of the other terrestrial planets and the Moon. The work of experimental petrologists has laid a foundation on which modern understanding of igneous and metamorphic processes has been built.

References

  • Best, Myron G. (2002), Igneous and Metamorphic Petrology (Blackwell Publishing). ISBN 1-4051-0588-7
  • Blatt, Harvey; Tracy, Robert J.; Owens, Brent (2005), Petrology: igneous, sedimentary, and metamorphic (New York: W. H. Freeman). ISBN 978-0-7167-3743-8
  • Dietrich, Richard Vincent; Skinner, Brian J. (2009), Gems, Granites, and Gravels: knowing and using rocks and minerals (Cambridge University Press). ISBN 978-0-521-10722-8
  • Fei, Yingwei; Bertka, Constance M.; Mysen, Bjorn O. (eds.) (1999), Mantle Petrology: field observations and high-pressure experimentation (Houston TX: Geochemical Society). ISBN 0-941809-05-6
  • Philpotts, Anthony; Ague, Jay (2009), Principles of Igneous and Metamorphic Petrology (Cambridge University Press). ISBN 978-0-521-88006-0
  • Robb, L. (2005), Introduction to Ore-Forming Processes (Blackwell Science). ISBN 978-0-632-06378-9