A review of the 2500 Ma span of alkaline-ultramafic, potassic and carbonatitic magmatism in West Greenland

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doi: 10.1016/0024-4937(92)90015-Q
Authors:Larsen, L. M.; Rex, D. C.
Author Affiliations:Primary:
Gronlands Geol. Undersogelse, Copenhagen, Denmark
Volume Title:Potassic and ultrapotassic magmas and their origin; Sixth meeting of the European Union of Geosciences (EUG VI)
Volume Authors:Foley, S., editor; Peccerillo, A.
Source:Lithos (Oslo), 28(3-6), p.367-402; Sixth meeting of the European Union of Geosciences; Potassic and ultrapotassic magmas and their origin, Strasbourg, France, March 1991, edited by S. Foley and A. Peccerillo. Publisher: Elsevier, Amsterdam, International. ISSN: 0024-4937
Publication Date:1992
Note:In English; illus. incl. 6 tables, 40 anals.
Summary:Kimberlites, carbonatites and ultramafic, mafic and potassic lamprophyres have been produced in W Greenland in recurrent events since the Archaean. Five distinct age groups are recognized: Archaean (> 2500 m.y.), early Proterozoic (1700-1900 m.y.), middle Proterozoic (Gardar, approx 1100-1300 m.y.), late Proterozoic (600 m.y.) and Mesozoic- Tertiary (200-30 m.y.). The rocks comprise two large and four small carbonatite occurrences, four kimberlite dyke swarms, one lamproite dyke swarm and one lamproite pipe, one dyke swarm of potassic lamprophyre and some ten dyke swarms of ultramafic lamprophyre and monchiquite. Geochemical data for the various rock groups are presented. Some of the carbonatites may represent relatively unmodified mantle-derived melts. The kimberlites range from primitive to differentiated compositions, and there are regional differences between kimberlites within Archaean and Proterozoic basement. The ultrapotassic lamproites and shonkinites have strong negative Nb spikes in their trace element spectra. The ultramafic and monchiquitic lamprophyres encompass a large compositional variation; however, several of the dyke swarms have individual chemical characters. The rocks are very unevenly distributed, indicating a lithospheric control, probably by old weakness zones providing access to the surface. The kimberlites are considered to be mainly of asthenospheric derivation. The regional differences are interpreted in terms of melting with phlogopite as a residual phase, with smaller degrees of melting at deeper levels beneath the Archaean lithosphere than beneath the Proterozoic. The ultrapotassic lamproites and shonkinites occur almost exclusively within a continental collision zone with possible two-way subduction and they are interpreted as mainly of lithospheric derivation, with a contribution from a subducted slab. Data for the other rock types are equivocal. Except for the Archaean rocks, the age groups can be related to major geotectonic events. The early Proterozoic group is related to continental collision at 1850 m.y. and subsequent rifting; the middle Proterozoic group is related to continental rifting and the Mesozoic group is related to continental rifting prior to continental break-up in the Tertiary. The 600 m.y. kimberlites and carbonatite are envisaged as cratonic, extra-rift activity in relation to continental break- up and formation of the Iapetus ocean, perhaps with a common cause in a broad, impinging mantle plume. [E.W.P.]
Subjects:Carbonatites; Cenozoic; Igneous rocks; Kimberlite; Lamproite; Lamprophyres; Mafic composition; Major elements; Mesozoic; Plate collision; Plate tectonics; Plutonic rocks; Precambrian; Review; Rifting; Shonkinite; Syenites; Tertiary; Trace elements; Ultramafic composition; Arctic region; Greenland; West Greenland
Abstract Numbers:94M/3664
Record ID:1993036171
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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