petrology

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pe·trol·o·gy / pəˈträləjē/ • n. the branch of science concerned with the origin, small-scale structure, and composition of rocks. Compare with lithology, petrography. DERIVATIVES: pet·ro·log·ic / ˌpetrəˈläjik/ adj. pet·ro·log·i·cal / ˌpetrəˈläjikəl/ adj. pe·trol·o·gist / -jist/ n.

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petrology, branch of geology specifically concerned with the origin, composition, structure, and properties of rocks, primarily igneous and metamorphic, and secondarily sedimentary. It includes petrography, the systematic description and classification of rocks using microscopic examination of rock in thin sections; and petrogenesis, which deals with the origin and formation of the various kinds of rock. Petrology is also concerned with the laboratory simulation of rock-forming processes and the application of principles of physical chemistry to natural environments. Petrologic analyses of oceanic rocks have given insights into plate tectonic processes, especially rock from mid-oceanic ridges, which may be formed from magma derived from deep in the mantle. Lunar rocks returned by Apollo astronauts were studied with petrographic techniques providing a wealth of information on the makeup and origin of the moon.

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petrology The study of rocks in general, including their occurrence, field relations, structure, origins and history (petrogenesis), and their mineralogy and textures (petrography). It may usefully be qualified as ‘igneous petrology’, or ‘sedimentary petrology’.

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petrology Study of rocks, including their origin, chemical composition, and location. Formation of the three classes of rocks – igneous (of volcanic origin); sedimentary (deposited by water); and metamorphic (either of the other two changed by temperature and pressure) – is studied.