Petrogenetic relationship between Palaeoproterozoic tholeiitic dykes and associated high-Mg noritic dykes, Labrador, Canada

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doi: 10.1016/S0301-9268(96)00048-4
Authors:Cadman, Andrew C.; Tarney, John; Hamilton, Michael A.
Author Affiliations:Primary:
University of Leicester, Department of Geology, Leicester, United Kingdom
Geological Survey of Canada, Canada
Volume Title:Precambrian Research
Source:Precambrian Research, 82(1-2), p.63-84. Publisher: Elsevier, Amsterdam, International. ISSN: 0301-9268
Publication Date:1997
Note:In English. 89 refs.; illus., incl. 5 tables, sketch map
Summary:Trace-element and Sr-Nd isotopic studies of the Kikkertavak dyke swarm provide information on early sub-continental lithosphere development. There are three distinct chemical dyke types: two tholeiitic, one high-Mg norite. It is not possible to relate any group to another by simple fractional crystallization processes, nor can they be derived by contaminating asthenospheric magma with local crustal components. From their Sr-Nd characteristics, combined with their REE and multi-element patterns, it appears that significant heterogeneity existed in the magma source regions at the time of generation, and that the processes responsible can be linked with the phase of crustal growth in the region at ∼ 3000 m.y. Modelling suggests that the observed compositions can be explained by lower lithosphere-asthenosphere mantle sources variably depleted by previous episodes of magma extraction, and then re-enriched. High-Mg noritic dykes are fairly common worldwide in the Palaeoproterozoic and are often broadly coeval with tholeiitic dykes, but are much less common in younger dyke suites. Most have compositions which require a refractory major-element composition coupled with marked re-enrichment in incompatible lithophile elements. Recent models for cyclic mantle overturns with related deep mantle plumes begin to provide the right environment beneath immature lithosphere which could generate the dyke-types observed. [R.E.S.]
Subjects:Alkaline earth metals; Asthenosphere; Dike swarms; Dikes; Fractional crystallization; Gabbros; Genesis; Geochemistry; Igneous rocks; Intrusions; Lithophile elements; Lithosphere; Magmas; Magnesium; Major elements; Mantle; Mantle plumes; Mass spectra; Melting; Melts; Metals; Nd/Nd; Norite; Outcrops; Paleoproterozoic; Partition coefficients; Plate tectonics; Plutonic rocks; Precambrian; Proterozoic; Rare earths; Spectra; Sr/Sr; Subduction; Tholeiitic composition; Trace elements; Upper Precambrian; Canada; Eastern Canada; Labrador; Newfoundland; Hopedale Block; Kikkertavak Dikes
Abstract Numbers:98M/570
Record ID:1997063632
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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