Abstract
An alkaline province has been found to constitute a significant part of the Archaean terraines in the Skjoldungen area, 63°N in South-East Greenland. A total of twenty-four alkaline complexes and syenite gneiss areas has been identified. The alkaline magmatism is regarded as syn- to post-tectonic to judge from the wide variation in the degree of deformation. A large number of intrusions are virtually undeformed. Petrographically the province encompasses slightly SiO2-undersaturated mafic to SiO2-saturated syenitic rocks and a carbonatite-bearing nephelinitic complex. Neodymium-samarium model ages and a zircon age show the alkaline rocks to be c. 2800 Ma old and the province thus constitutes the largest group of Archaean alkaline rocks yet found on Earth. The chemical characteristics, including very low concentrations of most trace elements except Ba and Sr, recall those of the younger alkaline Seiland province in Norway and the Haliburton-Bancroft province in Canada.
Highlights
An alkaline provinee has been found to constitute a significant part of the Archaean terraines in the Skjoldungen area, 63°N in South-East Greenland
The Archaean terrains in South-East Greenland can be divided into three areas: (1) a southern area dominated by granulite and amphibolite facies agmatitic gneisses; (2) a northern area dominated by non-agmatitic gneisses and supracrustal series mainly in amphibolite facies and (3) a central area transitional between (1) and (2), characterised by strong linear deformation and the occurrence of the alkaline rocks of the Skjoldungen alkaline province (Nielsen & Escher, 1988; Rosing et al, 1988)
Ince, and samples from most of the visited complexes and syenitic gneiss areas have been analysed to ensure their chemical affinity to the alkaline province
Summary
An alkaline provinee has been found to constitute a significant part of the Archaean terraines in the Skjoldungen area, 63°N in South-East Greenland. Areas with syenitic gneisses are found up to 70 km south of this zone, and the alkaline complexes have been observed up to 30 km south of the zone; no intrusions were observed north of the zone The syenitic gneiss areas and intrusive complexes are deformed and foliated to variable extents and are syn- to post-tectonic.
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