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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
The newly discovered Jurassic Tikiusaaq carbonatite-aillikite occurrence, West Greenland, and some remarks on carbonatite-kimberlite relationships
Lithos, Volume 112, Year 2009
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Description
We discuss mineral chemistry data and report ten high-precision U-Pb (zircon, baddeleyite, pyrochlore, and perovskite) and Rb-Sr phlogopite ages for the newly discovered Tikiusaaq carbonatite intrusion and associated ultramafic dykes from the North Atlantic craton, West Greenland. At Tikiusaaq, massive dolomite-calcite carbonatite sheets intruded an 2 × 3 km area along a ductile shear zone between ca. 158 and 155 Ma. The accompanying carbonatite and carbonate-rich ultramafic silicate dykes were emplaced between ca. 165 and 157 Ma in close proximity to this carbonatite centre utilizing pre-existing brittle fractures. The deep volatile-rich magmatism at Tikiusaaq forms part of a larger Jurassic alkaline province in southern West Greenland and represents the earliest manifestation of rifting processes related to the opening of the Mesozoic-Cenozoic Labrador Sea Basin. Although the ultramafic silicate dykes macroscopically resemble hypabyssal kimberlites, they are identified as kimzeyite-bearing monticellite aillikites (carbonate-rich ultramafic lamprophyres) using a modern mineralogical-genetic classification. The overlapping emplacement ages of the carbonatite sheets and aillikite dykes, along with the carbonate-rich nature of the latter, suggest a genetic relationship between these magma types. The aillikites carry garnet peridotite xenoliths and have mineralogical characteristics of primitive magmas such as highly forsteritic olivine (up to Fo90 mol%) and Cr-rich spinel (up to 46 wt.% Cr2O3) microphenocrysts; whereas the carbonatite sheets reveal a higher degree of differentiation such as Fe-rich dolomite compositions (up to 9 wt.% FeO). The initial findings reported here from Tikiusaaq suggest that a link between these magma types by an increasing degree of partial melting of a common carbonated upper mantle peridotite source region, as commonly envisaged for the compositionally similar Sarfartoq complex, is untenable. Rather, proto-aillikite magma may be parental to the dolomitic carbonatite sheets, but the nature of the carbonate separation mechanism(s) is presently not understood. © 2009 Elsevier B.V. All rights reserved.
Authors & Co-Authors
Tappe, Sebastian
Canada, Edmonton
University of Alberta
United Kingdom, London
De Beers Group
Steenfelt, Agnete
Denmark, Copenhagen
Geological Survey of Denmark and Greenland
Heaman, Larry M.
Canada, Edmonton
University of Alberta
Simonetti, Antonio
United States, Notre Dame
University of Notre Dame
Statistics
Citations: 102
Authors: 4
Affiliations: 4
Identifiers
Doi:
10.1016/j.lithos.2009.03.002
ISSN:
00244937
Research Areas
Genetics And Genomics
Violence And Injury