Proterozic basalt dikes in the Nain anorthosite complex, Labrador

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doi: 10.1139/e85-117
Authors:Wiebe, R. A.
Author Affiliations:Primary:
Franklin and Marshall Coll., Lancaster, PA, United States
Volume Title:Canadian Journal of Earth Sciences Revue Canadienne des Sciences de la Terre
Source:Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 22(8), p.1149-1157. Publisher: National Research Council of Canada, Ottawa, ON, Canada. ISSN: 0008-4077
Publication Date:1985
Note:In English with French summary. 32 refs.; illus. incl. 5 tables, sketch map
Summary:Two sets of Proterozoic (1290-1042 m.y.) alkali to transitional basaltic dykes occur sparsely in an area of = or >5000 km2 within the complex. Both are compositionally similar in terms of major elements, but the set trending roughly N-S contains much higher concentrations of incompatible elements than the more abundant dykes trending roughly ENE-WSW. Both types have low normative clinopyroxene relative to olivine - a characteristic shared with widespread troctolitic rocks in the Nain complex. Low Mg numbers and low Ni contents suggest that the magmas producing the dykes have undergone extensive fractional crystallization; the low normative diopside content suggests that it occurred at depths equivalent to = or >10 kbar (1000 MPa). High equilibration T for coexisting Fe-Ti oxides in the matrices of the dykes indicate that they cooled rapidly and were emplaced near the surface. The exposed level of the Nain anorthosite complex (emplaced at depths of 8-10 km) indicates that the anorthosites were uplifted and eroded relatively soon after their emplacement, i.e. prior to dyke emplacement. [J.M.H.]
Subjects:Alkali basalts; Anorthosite; Basalts; Chain silicates; Clinopyroxene; Differentiation; Dikes; Emplacement; Fractional crystallization; Gabbros; Geochemistry; Igneous rocks; Intrusions; Magmas; Major elements; Metals; Mineral composition; Nesosilicates; Olivine; Olivine group; Orthosilicates; Petrology; Plutonic rocks; Pyroxene group; Rare earths; Silicates; Trace elements; Troctolite; Volcanic rocks; Canada; Eastern Canada; Labrador; Nain Massif; Newfoundland
Coordinates:N560000 N570000 W0610000 W0620000
Abstract Numbers:86M/2416
Record ID:1985083931
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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