ISSN:
1437-3262
Schlagwort(e):
L. Palaeozoic volcanics
;
Amphibolites
;
Geochemistry
;
Petrogenesis
;
Crustal contamination
;
Palaeotectonic environment
;
Orlica-Śnieżnik dome, Bohemian massif
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Geologie und Paläontologie
Notizen:
Abstract Orthoamphibolites within and marginal to the Orlica-Śnieżnik dome in the eastern Bohemian massif are associated with a series of Proterozoic-Lower Palaeozoic supracrustal meta-sediments of the Stronie, Nové Město and Staré Město formations. Massive and variably foliated amphibolites range from common epidote-plagioclase-blue-green/green hornblende varieties to assemblages with diopside, garnet and brown amphibole. All the amphibolites have a basaltic composition and are divided into three main chemical groups which are intimately associated in the field: main series tholeiites, low-Ti tholeiites and alkali basalts. All groups exhibit a common enrichment in LIL elements+Nb+Ta (relative to high-field-strength elements) which reflects contamination by upper continental crust and/or pelagic sediment compositions. The gross chemistry of the tholeiitesapproaches that for MORB, although the geological environment and nature of crustal contamination suggests that the basaltic precursors were probably emplaced in a rifted ensialic basinal environment. If the amphibolites are representative of an early phase of the Lower Palaeozoic fragmentation of Gondwanaland, then rifting did not fully develop ocean crust. The wider significance of the chemical interpretation implies that some of the variation from Variscan Proterozoic-Palaeozoic metabasite suites that is ascribed to a complex of different eruptive settings could be accounted for by variable contamination and/or source composition.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF02422230
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