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The Skaergaard intrusion is a layered igneous intrusion in East Greenland. It comprises various rock types including gabbro, ferro diorite, anorthosite and granophyre. Discovered by Lawrence Wager〔Brooks, CK (2005) ''The Skaergaard intrusion: from icon to precious metal deposit''. Geology Today, v. 21, p. 218-221.〕 in 1931 during the British Arctic Air Route Expedition led by Gino Watkins, the intrusion has been important to the development of key concepts in igneous petrology, including magma differentiation and fractional crystallisation〔Wager, LR, Deer, WA (1939) ''Geological investigations in East Greenland Part III. The petrology of the Skaergaard Intrusion, Kangerdlugssuaq''. Meddelselser om Grønland, v. 105, 346 pp.〕〔McBirney, AR (1975) ''Differentiation of the Skaergaard intrusion''. Nature, v. 253, p. 691-694.〕 and the development of layering.〔Wager, LR, Brown, GM (1967) Layered Igneous Rocks. WH Freeman, San Francisco, 588 pp.〕〔McBirney, AR, Noyes, RM (1975) ''Crystallization and Layering of the Skaergaard Intrusion''. Journal of Petrology, v. 20, p. 487-554.〕 The Skaergaard intrusion formed when tholeiitic magma was emplaced about 55 million years ago,〔Brooks, CK, Gleadow, AJW (1977) ''A fission-track age for the Skaergaard intrusion and the age of the East Greenland basalts''. Geology, v. 5, p. 539-540.〕 during the initial opening of the North Atlantic Ocean. The body represents essentially a single pulse of magma, which crystallized from the bottom upward and the top downward. The intrusion is characterized by exceptionally well-developed cumulate layering defined by variations in the abundance of crystallizing olivine, pyroxene, plagioclase and magnetite. The Skaergaard is perhaps the simplest and smallest of a group of gabbroic complexes of similar age that occur along the central coast of East Greenland, which together with coeval flood basalts are part of the North Atlantic large igneous province. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Skaergaard intrusion」の詳細全文を読む スポンサード リンク
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