Abstract
Major and trace element chemistry, and Sr and Pb-isotope data are presented for a 400 km long and ca. 100 m wide basic dyke in the Rinkian mobile belt of West Greenland. The dyke is relatively alkaline in composition (Na2O+K2O:4.0–5.5%) but silica saturated (SiO2:47–49%). Its age is determined as 1,645±35 Ma (Rb-Sr whole-rock isochron, initial 87Sr/86Sr ratio 0.7028±0.0001) and the Pb-isotope data indicate a source with model μ1= 8.00±0.02. Although the dyke cuts very diverse Archaean and Proterozoic country rocks, it displays a high degree of chemical and isotopic homogeneity along its entire outcrop and has probably not suffered any significant crustal contamination. The dyke shows a distinct chemical zonation, and variations in composition across the dyke at individual localities are often greater than variations between chill samples along the dyke. Chemical homogeneity of the dyke is consistent with two models: (1) rapid lateral emplacement from a localised intrusive centre, or (2) derivation of the magma from a deep, homogeneous mantle source of great extent. Both models pose severe problems, and the evidence does not permit a reliable choice between them.
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Kalsbeek, F., Taylor, P.N. Chemical and isotopic homogeneity of a 400 km long basic dyke in central West Greenland. Contr. Mineral. and Petrol. 93, 439–448 (1986). https://doi.org/10.1007/BF00371714
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DOI: https://doi.org/10.1007/BF00371714