Orbicular lamprophyre from Vestby, southeast Norway
1975; Elsevier BV; Volume: 8; Issue: 2 Linguagem: Inglês
10.1016/0024-4937(75)90019-5
ISSN1872-6143
AutoresInge Bryhni, Johannes A. Dons,
Tópico(s)Geology and Paleoclimatology Research
ResumoA pyroxene-amphibole lamprophyre of Permian age intersecting Precambrian gneiss, etc., contains domains of pyroxenite breccia and of closely packed single- and multi-shelled orbicules. The multi-shelled orbicules have inner medium-grained, radial and outer aphanitic, laminated shells. The outer shells are explained as having formed by direct precipitation from the magma. The inner shells most probably underwent a recrystallization at magmatic temperatures, their original composition being like that of the outer shells. Shells of single-shelled orbicules are similar to the inner shell of the multi-shelled ones and contain relicts of aphanitic, laminated material. The cores, composed of Permian pyroxenite or more rarely Precambrian pegmatite quartz, were originally formed by volcanic fragmentation of the country rock.
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