Signatur:
ZSP-164-62
In:
The geology of the South Orkney Islands
Beschreibung / Inhaltsverzeichnis:
Signy Island, the best known of the South Orkney Islands, is composed of a regionally metamorphosed sequence of marbles, para-amphibolites and quartz-mica-schists (the Basement Complex of probable Precambrian age), whose stratigraphical succession has been established by earlier workers. These rocks, which have undergone post-kinematic crystallization, belong to the albite-epidote-amphibolite facies, and they probably represent crystallization at a higher grade of metamorphism than the rocks situated to the north on Coronation Island; retrograde metamorphism is purely a local phenomenon. It is believed that these metamorphic rocks were originally sediments of epicontinental facies, i.e. quartzites, mudstones, marls and limestones, and that during metamorphism they underwent a sequence of vein mineralization which was both pre- and post- kinematic. In spite of the widespread veining, there is no conclusive evidence of igneous activity on Signy Island. Only one phase of crystallization is indicated by the rocks examined, although K-Ar age determinations have shown that a much later and more feeble orogeny, which released radiogenic argon, affected these rocks approximately 185±7 m.yr. ago. The metamorphic rocks of the South Orkney Islands are lithologically and petrologically comparable with those of the Elephant and Clarence Islands group, but they differ from the Basement Complex of the Antarctic Peninsula, where orthogneisses are present.
Materialart:
Schriftenreihen ausleihbar
Seiten:
30 S. : Ill., Kt.
Serie:
62
URL:
http://www.antarctica.ac.uk/about_bas/publications/scientific_reports/index.php
Zweigbibliothek:
AWI Bibliothek
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