Zusammenfassung
In seiner neuesten Klassifikation der Anorthosite hatBerrangé (1966) die west-grönländischen Anorthosite als orogen-plutonische Typen interpretiert. Neueste Studien haben jedoch gezeigt, daß in den zentralen, hochmetamorphen Gebieten von Fiskenaesset fast alle Anorthosite zahlreiche Chromiteinlagerungen aufweisen. Die Anorthosite sind unter Granulit-Fazies metamorphisiert und anschließend diaphthoritisch überprägt worden. Man kann daraus folgern, daß die west-grönländischen Anorthosite im Ganzen als präorogene, schichtige Typen zu klassifizieren sind und daß die meisten der heutigen Merkmale sekundären Ursprungs sind, und nicht mit den orogen-plutonischen Anorthositen verwechselt werden dürfen.
Abstract
In his recent classification of anorthosites,Berrange(1966) has interpreted the West Greenland anorthosites as orognic-plutonic types. However, recent work has shown that in the central high-grade region of Fiskenaesset nearly all the anorthosite horizons have intense chromite layering. The anorthosites have been metamorphosed under granulite facies conditions and subsequently downgraded. The conclusions are made that the West Greenland anorthosites as a whole should be classified as pre-orogenic stratiform types and that most of the present features are of secondary origin and should not be confused with those of the orogenic-plutonic association.
Résumé
Dans sa classification récente des anorthosites,Berrangé (1966) a interprété les anorthosites du Groenland occidental comme appartenant au genre orogénique-plutonique. Des récents travaux ont cependant montré que presque tout les horizons d'anorthosite dans la région centrale gneissique de Fiskenaesset possèdent de nombreuses intercalations de chromite. Les anorthosites ont été métamorphosées sous des conditions de faciès granulitique et par la suite ont subi un métamorphisme rétrograde. Pour conclure, il semble que les anorthosites du Groenland occidental en général doivent être classifiées comme étant du genre pré-orogénique stratiforme, et que la majorité des caractéristiques actuelles sont d'origine secondaire et ne doivent pas être confondues avec celles des associations orogéniques-plutoniques.
Краткое содержание
В своей новейшей клас сификации анортозит ов Berrange' (1966) рассматривал происхождение анорт озитов западной Грен ландии, как орогенноплутоничес кое. Новейшие исследован ия доказали, что почти все анортозиты в центральных област ях в окрестностях Фис кенессет, подвергшихся сильно му метаморфизму, содерж ат в себе хромит. Анорт озиты подвергались метаморфизированию при образовании гран улитовой структуры, после чего имели место диаф торитовые преобразо вания. Из этого вытекает, что анартозиты западной Гренландии следует рассматривать, как до-орогенные слоистые структуры, и что большинство нахо димых сегодня признаков недавнего происхожд ения и их поэтому нель зя смешивать с орогенно плутоническими анортозитами.
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Windley, B.F. On the classification of the West Greenland anorthosites. Geol Rundsch 56, 1020–1026 (1967). https://doi.org/10.1007/BF01848777
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DOI: https://doi.org/10.1007/BF01848777