Mafic silicates from the nepheline syenites of the Motzfeldt centre
ABSTRACT. At least five successive intrusions of nephe-line-bearing magmas fractionated in situ and developed repeatedly overlapping, yet distinct chemical trends in the mafic silicates. Representative el ctron probe analyses are given for olivine, clinopyroxene, amphibole, biotite, and aenigmatite...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.617.2650 2023-05-15T16:29:53+02:00 Mafic silicates from the nepheline syenites of the Motzfeldt centre A. P. Jones The Pennsylvania State University CiteSeerX Archives 1984 application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.617.2650 http://www.minersoc.org/pages/Archive-MM/Volume_48/48-346-1.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.617.2650 http://www.minersoc.org/pages/Archive-MM/Volume_48/48-346-1.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://www.minersoc.org/pages/Archive-MM/Volume_48/48-346-1.pdf text 1984 ftciteseerx 2016-01-08T14:48:01Z ABSTRACT. At least five successive intrusions of nephe-line-bearing magmas fractionated in situ and developed repeatedly overlapping, yet distinct chemical trends in the mafic silicates. Representative el ctron probe analyses are given for olivine, clinopyroxene, amphibole, biotite, and aenigmatite and their variations discussed. Increasing Na with fractionation produced aegirine-rich clinopyroxene and caused Na/K in amphibole to increase from 2.4 to 7.0. Si~/AI z increased in both amphibole and in the less abundant mica. Mn-enrichment is common to all of the mafic silicates, including the olivines and it is suggested that the parent magmas were initially Mn-rich. Mineralogically the Motzfeldt centre is evolved and similar to the other centres in the Igaliko complex. However, the Motzfeldt centre contains the most frac-tionated rocks (lujavrites) and is in this respect similar to the peralkaline Ilimaussaq intrusion. The compositional ranges and trends of the mafic silicates in Motzfeldt hus provide links between the uncommon peralkaline plutons and the more abundant and typical nepheline syenites. THE PROCESSES which lead to the emplacement of large plutonic 'batholiths ' of alkaline and per-alkaline magma into shallow levels of the crust are poorly understood. Good exposures throughout the Gardar province in southern Greenland (for general description see Upton, 1974; Emeleus and Upton, 1976) give a clear indication of prolonged Proterozoic alkaline magmatism ( ~ 1350-1150Ma) associated with tectonic tilting, which produced many plutonic centres. The dominant message which comes from the studies of these centres is one of multiple overlapping intrusions. Vertical sec-tions to a height of nearly 2 km are typical, no bases Text Greenland Igaliko Unknown Greenland Ilimaussaq ENVELOPE(-45.900,-45.900,60.983,60.983) Tilting ENVELOPE(-54.065,-54.065,49.700,49.700) |
institution |
Open Polar |
collection |
Unknown |
op_collection_id |
ftciteseerx |
language |
English |
description |
ABSTRACT. At least five successive intrusions of nephe-line-bearing magmas fractionated in situ and developed repeatedly overlapping, yet distinct chemical trends in the mafic silicates. Representative el ctron probe analyses are given for olivine, clinopyroxene, amphibole, biotite, and aenigmatite and their variations discussed. Increasing Na with fractionation produced aegirine-rich clinopyroxene and caused Na/K in amphibole to increase from 2.4 to 7.0. Si~/AI z increased in both amphibole and in the less abundant mica. Mn-enrichment is common to all of the mafic silicates, including the olivines and it is suggested that the parent magmas were initially Mn-rich. Mineralogically the Motzfeldt centre is evolved and similar to the other centres in the Igaliko complex. However, the Motzfeldt centre contains the most frac-tionated rocks (lujavrites) and is in this respect similar to the peralkaline Ilimaussaq intrusion. The compositional ranges and trends of the mafic silicates in Motzfeldt hus provide links between the uncommon peralkaline plutons and the more abundant and typical nepheline syenites. THE PROCESSES which lead to the emplacement of large plutonic 'batholiths ' of alkaline and per-alkaline magma into shallow levels of the crust are poorly understood. Good exposures throughout the Gardar province in southern Greenland (for general description see Upton, 1974; Emeleus and Upton, 1976) give a clear indication of prolonged Proterozoic alkaline magmatism ( ~ 1350-1150Ma) associated with tectonic tilting, which produced many plutonic centres. The dominant message which comes from the studies of these centres is one of multiple overlapping intrusions. Vertical sec-tions to a height of nearly 2 km are typical, no bases |
author2 |
The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
A. P. Jones |
spellingShingle |
A. P. Jones Mafic silicates from the nepheline syenites of the Motzfeldt centre |
author_facet |
A. P. Jones |
author_sort |
A. P. Jones |
title |
Mafic silicates from the nepheline syenites of the Motzfeldt centre |
title_short |
Mafic silicates from the nepheline syenites of the Motzfeldt centre |
title_full |
Mafic silicates from the nepheline syenites of the Motzfeldt centre |
title_fullStr |
Mafic silicates from the nepheline syenites of the Motzfeldt centre |
title_full_unstemmed |
Mafic silicates from the nepheline syenites of the Motzfeldt centre |
title_sort |
mafic silicates from the nepheline syenites of the motzfeldt centre |
publishDate |
1984 |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.617.2650 http://www.minersoc.org/pages/Archive-MM/Volume_48/48-346-1.pdf |
long_lat |
ENVELOPE(-45.900,-45.900,60.983,60.983) ENVELOPE(-54.065,-54.065,49.700,49.700) |
geographic |
Greenland Ilimaussaq Tilting |
geographic_facet |
Greenland Ilimaussaq Tilting |
genre |
Greenland Igaliko |
genre_facet |
Greenland Igaliko |
op_source |
http://www.minersoc.org/pages/Archive-MM/Volume_48/48-346-1.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.617.2650 http://www.minersoc.org/pages/Archive-MM/Volume_48/48-346-1.pdf |
op_rights |
Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
_version_ |
1766019600202334208 |