Archaean megacrystic plagioclase units and the tectonic setting of greenstones
Large (up to 20 cm), equidimensional, commonly euhedral, plagioclase megacrysts of highly calcic composition (An sub 80-90) occur commonly in all Archean cratons in one or more of three distinct associations: (1) as cumulate crystal segregations of anorthosite or as megacrysts in basaltic dikes, sil...
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1986
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ftnasantrs:oai:casi.ntrs.nasa.gov:19860013651 2023-05-15T13:21:42+02:00 Archaean megacrystic plagioclase units and the tectonic setting of greenstones Phinney, W. C. Morrison, D. A. Maczuga, D. Unclassified, Unlimited, Publicly available Jan 1, 1986 application/pdf http://hdl.handle.net/2060/19860013651 unknown Document ID: 19860013651 Accession ID: 86N23122 http://hdl.handle.net/2060/19860013651 No Copyright CASI GEOPHYSICS Lunar and Planetary Inst. Workshop on the Tectonic Evolution of Greenstone Belts; p 94-96 1986 ftnasantrs 2016-06-11T22:52:25Z Large (up to 20 cm), equidimensional, commonly euhedral, plagioclase megacrysts of highly calcic composition (An sub 80-90) occur commonly in all Archean cratons in one or more of three distinct associations: (1) as cumulate crystal segregations of anorthosite or as megacrysts in basaltic dikes, sills, and flows in greenstone belts that vary in metamorphic grade from greenschist to granulite. Throughout 100's of thousands of square kilometers of northwestern Ontario and Manitoba the plagioclase megacrysts occur in pillowed and massive flows, sills, dikes, large inclusions in dikes, and intrusive anorthositic complexes with areas of up to a few 100 sq km and spanning a period of at least 100 m.y. in the 2.7 to 2.8 b.y. time frame; (2) as basaltic dike swarms in stable cratonic areas forming parallel to subparallel patterns over hundreds of thousands of square kilometers intruding both granitic gneisses and supracrustal belts including greenstones. These swams include the Ameralik-Saglek system at 3.1 to 3.4 b.y., the Matachewan system at 2.5 to 2.6 b.y., and the Beartooth-Bighorn system at 2.2 to 2.3 b.y.; and, (3) as anorthositic complexes associated with marbles and quartzites (Sittampundi, India and Messina, South Africa) in granulite grade terrains. Initial attempts to correlate tectonic settings of similar modern crystbearing units with their Archean counterparts were only partially successful. Other/Unknown Material Ameralik NASA Technical Reports Server (NTRS) Ameralik ENVELOPE(-51.000,-51.000,64.117,64.117) |
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Open Polar |
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NASA Technical Reports Server (NTRS) |
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ftnasantrs |
language |
unknown |
topic |
GEOPHYSICS |
spellingShingle |
GEOPHYSICS Phinney, W. C. Morrison, D. A. Maczuga, D. Archaean megacrystic plagioclase units and the tectonic setting of greenstones |
topic_facet |
GEOPHYSICS |
description |
Large (up to 20 cm), equidimensional, commonly euhedral, plagioclase megacrysts of highly calcic composition (An sub 80-90) occur commonly in all Archean cratons in one or more of three distinct associations: (1) as cumulate crystal segregations of anorthosite or as megacrysts in basaltic dikes, sills, and flows in greenstone belts that vary in metamorphic grade from greenschist to granulite. Throughout 100's of thousands of square kilometers of northwestern Ontario and Manitoba the plagioclase megacrysts occur in pillowed and massive flows, sills, dikes, large inclusions in dikes, and intrusive anorthositic complexes with areas of up to a few 100 sq km and spanning a period of at least 100 m.y. in the 2.7 to 2.8 b.y. time frame; (2) as basaltic dike swarms in stable cratonic areas forming parallel to subparallel patterns over hundreds of thousands of square kilometers intruding both granitic gneisses and supracrustal belts including greenstones. These swams include the Ameralik-Saglek system at 3.1 to 3.4 b.y., the Matachewan system at 2.5 to 2.6 b.y., and the Beartooth-Bighorn system at 2.2 to 2.3 b.y.; and, (3) as anorthositic complexes associated with marbles and quartzites (Sittampundi, India and Messina, South Africa) in granulite grade terrains. Initial attempts to correlate tectonic settings of similar modern crystbearing units with their Archean counterparts were only partially successful. |
format |
Other/Unknown Material |
author |
Phinney, W. C. Morrison, D. A. Maczuga, D. |
author_facet |
Phinney, W. C. Morrison, D. A. Maczuga, D. |
author_sort |
Phinney, W. C. |
title |
Archaean megacrystic plagioclase units and the tectonic setting of greenstones |
title_short |
Archaean megacrystic plagioclase units and the tectonic setting of greenstones |
title_full |
Archaean megacrystic plagioclase units and the tectonic setting of greenstones |
title_fullStr |
Archaean megacrystic plagioclase units and the tectonic setting of greenstones |
title_full_unstemmed |
Archaean megacrystic plagioclase units and the tectonic setting of greenstones |
title_sort |
archaean megacrystic plagioclase units and the tectonic setting of greenstones |
publishDate |
1986 |
url |
http://hdl.handle.net/2060/19860013651 |
op_coverage |
Unclassified, Unlimited, Publicly available |
long_lat |
ENVELOPE(-51.000,-51.000,64.117,64.117) |
geographic |
Ameralik |
geographic_facet |
Ameralik |
genre |
Ameralik |
genre_facet |
Ameralik |
op_source |
CASI |
op_relation |
Document ID: 19860013651 Accession ID: 86N23122 http://hdl.handle.net/2060/19860013651 |
op_rights |
No Copyright |
_version_ |
1766360999401619456 |