The geochemistry and petrology of an alkaline lamprophyre sheet intrusion complex on Maio, Cape Verde Republic

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doi: 10.1144/gsjgs.144.2.0227
Authors:Furnes, H.; Stillman, C. J.
Author Affiliations:Primary:
Geol. Inst., Bergen, Norway
Trinity Coll., Dep. Geol., United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 144(2), p.227-241. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1987
Note:In English. 33 refs.; illus. incl. 5 tables, geol. sketch map
Summary:The island has a basement complex of Mesozoic and Tertiary age which is invaded by an intense swarm of sheet intrusions 16-18 m.y. old. They consist of sills and dykes of alkaline lamprophyre many of which are aphyric or sparsely porphyritic. Phenocrysts are mainly clinopyroxene with minor olivine and Ti-magnetite, and microphenocrysts are kaersutite, apatite and biotite. K-feldspar and analcite dominate the groundmass. Chemically the intrusions are basanitic their compositions being comparable to the Neogene and Pleistocene basanitic lavas which cap the island. It is suggested that the liquids from which the sheet intrusions crystallized may have been derived from a range of basanitic parents similar to those from which the later lavas were generated, but modified by water-rock interactions enhanced by trapped volatiles. [R.E.S.]
Subjects:Absolute age; Alkalic composition; Cenozoic; Dates; Differentiation; Emplacement; Fractional crystallization; Geochemistry; Geochronology; Igneous rocks; Intrusions; K/Ar; Lamprophyres; Magmas; Metals; Mineral composition; Petrology; Phenocrysts; Plutonic rocks; Rare earths; Swarms; Tertiary; Trace elements; Africa; Atlantic Ocean Islands; Cape Verde Islands; Central igneous complex; Intrusive rocks; Maio; Sheet intrusions
Abstract Numbers:87M/6690
Record ID:1987062739
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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