Cathodoluminescence Petrography of Middle Proterozoic Extrusive Carbonatite from Qasiarsuk, South Greenland

Christopher L. Hayward and Adrian P. Jones
Department of Geological Sciences, University College London, Gower Street, London WC1E 6BT

Abstract: The amygdaloidal carbonatite lavas at Qasiarsuk have a primary phenocryst assemblage of calcite, fluor-apatite and magnetite set in a groundmass of calcite, apatite and iron oxides, and minor dolomite. Cathodoluminescence reveals a complex history, both for the major minerals which show zonal growth, and for important Nb and REE accessory phases which include pyrochlore and perovskite. The REE reside in fluor/hydrous-carbonates included exclusively in apatite. These REE minerals are similar to synthetic phases from hydrothermal experiments, but probably crystallised in equilibrium with a late-stage volatile-rich carbonate melt. Apart from low-temperature alteration, the rocks have been little disturbed since their extrusion during the earliest phase of development of the Gardar Alkaline Igneous Province.

Keywords: cathodoluminescence petrography • carbonatite • Qasiarsuk, Greenland

Mineralogical Magazine; December 1991 v. 55; no. 381; p. 591-603; DOI: 10.1180/minmag.1991.055.381.12
© 1991, The Mineralogical Society
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