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The zone of alteration surrounding a body of igneous rock caused by heat and volatiles given off as the magma crystallized. Changes can be in mineralogy, texture, or elemental and isotopic composition of the original enclosing (country or wall) rocks, and progressively increase closer to the igneous contact. The contact aureole is the shell of metamorphosed or metasomatized rock enveloping the igneous body (see illustration). The ideal contact aureole forms locally around a single magma after it is emplaced. Metamorphism over a much larger area can result from coalescing of several contact aureoles. This is termed a contact-regional metamorphic aureole and is thought responsible for the regional metamorphism of several mountain areas. Other contact aureoles develop at greater depths and may be physically emplaced to shallower levels along with the igneous body. These are termed dynamothermal aureoles. See also Igneous rocks; Magma; Metamorphic rocks; Metamorphism; Metasomatism; Pluton.

Zoned contact aureole developed around an igneous body.

The aureole extends from the igneous contact, where the metamorphic effects are the greatest, out into the country rocks to where the temperature or heat energy is insufficient to effect any changes. This temperature lies between 400 and 750°F (200 and 400°C), and actual widths of contact aureoles range from several inches to miles.

Contact metamorphism can occur over a wide range of temperatures, pressures, or chemical gradients in rocks of any composition. Thus any mineral assemblage or facies of metamorphic rocks an be found. However, the nature of contact aureoles results in minerals characteristic of low to moderate pressures and moderate to high temperatures usually in common rock types: shales, basalt, limestone, and sandstone. Characteristic minerals developed in shales are andalusite, sillimanite, cordierite, biotite, orthopyroxene, and garnet. At the highest temperatures, tridymite, sanidine, mullite, and pigeonite form; whereas in limestone unusual calcium silicates form, including tilleyite, spurrite, rankinite, larnite, merwinite, akermanite, monticellite, and melilite. See also Facies (geology).

Compositional changes in a contact aureole range from none to great, but as a rule, contact metamorphism entails relatively little change in bulk rock composition. Because metamorphic changes are largely brought about by heat, contact aureoles are often termed thermal aureoles. However, there is a tendency for volatiles (water, carbon dioxide, oxygen) and alkalies (sodium, potassium) to be lost from rocks in the aureole. Stable isotope compositions (oxygen, sulfur) change in response to the thermal gradient and flow of fluids through the rocks. In some cases, volatiles (boron, fluorine, and chlorine) and other elements from the crystallizing magma are gained.

Some wall rock compositions, such as limestone, can be greatly changed and form rocks termed skarn. These contact aureoles are economically important because they often contain ore deposits of iron, copper, tungsten, graphite, zinc, lead, molybdenum, and tin. Conversely, the magma can incorporate material from the wall rocks by assimilation or mixing with any partial melts formed. Mixing results in elemental and isotopic contamination of the magma, crystallization of different minerals from the melt, and hybrid rock types at the margin of the igneous body. See also Ore and mineral deposits; Pneumatolysis; Skarn.

That area of rock altered in composition, structure, or texture by contact with an igneous intrusion. A metamorphic aureole surrounds the Dartmoor granite intrusion.

A pointed oval frame or glory around the head or body of a sacred figure; the radiance surrounding it.

Modern dance work in one act with choreography by Taylor, music by Handel, and lighting by T. Skelton. Premiered 4 Aug. 1962 at Connecticut College, New London, by the Paul Taylor Dance Company with Taylor, Elizabeth Walton, Wagoner, Sharon Kinney, and Renee Kimball. A lyrical buoyant dance which at the time marked Taylor's stylistic break from the American avant-garde. Its choreography fuses the blunt power of modern dance with the elevation of ballet, and at the time was seen as a rejection of the twin poles of modern dance then prevalent-the darkly dramatic and the abstractly cerebral. It has entered the repertories of many companies including Royal Danish Ballet (1968), Paris Opera Ballet (1974), and London Festival Ballet (1985).

Tutor's tip: A dentist fixes an "areole" (small pit or cavity) in your tooth. An astronomer studies the "areolas" (dark-colored rings) around Saturn and the "aureoles" or "aureolas" (rings of light) around eclipses.

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• Celestial Phenomena and Points - aureole: luminous area that surrounds sun as seen through thin cloud; corona
• Christianity - aureole: halo
• Occult States and Experiences - aureole: radiant light around head of sacred person; halo

Dansk (Danish)
n. - strålekrans, solgissel

Nederlands (Dutch)
aureool, lichtkring, stralenkrans

Français (French)
n. - (Art, Astron) auréole

Deutsch (German)
n. - Aureole, Heiligenschein, Nimbus

Ελληνική (Greek)
n. - άλως, φωτοστέφανος, (αστρον.) ηλιακή άλως, ηλιακό στέμμα

Italiano (Italian)
aureola

Português (Portuguese)
n. - auréola (f)

Русский (Russian)
ореол, сияние

Español (Spanish)
n. - aureola, halo, nimbo

Svenska (Swedish)
n. - helgongloria

中文（简体）(Chinese (Simplified))
光轮, 光环

中文（繁體）(Chinese (Traditional))
n. - 光輪, 光環

한국어 (Korean)
n. - 후광, 광륜, 코로나

日本語 (Japanese)
n. - 天上の宝冠, 栄光, オウレオール, 後光

العربيه (Arabic)
‏(الاسم) هاله‏

עברית (Hebrew)
n. - ‮הילה, נוגה, עטרת אור סביב השמש‬

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