gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1987.051.363.06 Mineralogy A New Natural Occurrence of Zirconolite (CaZrTi2O7) and Baddeleyite (ZrO2) in Basic Cumulates: The Laouni Layered Intrusion (Southern Hoggar, Algeria) Lorand J. P. Laboratoire de Minéralogie du Museum National d'Histoire, Naturelle de Paris, Unité associée au CNRS no. 286, 61 Rue Buffon, 75005 Paris, France Cottin J. Y. Départment de Géologie, IST Université d'Oran Essenia, Algeria 12 1987 51 363 671 676 24 11 1986 5 2 1987 Copyright © 1987, The Mineralogical Society 1987 Abstract

Four grains of zirconolite and baddeleyite have been found in two plagioclase-rich adcumulates from the Laouni layered intrusion (Southern Hoggar, Algeria). Zirconolite is poor in REE; baddeleyite is chemically close to ZrO2 and contains minor amounts of Hf. They are considered to be crystallization products of pockets of intercumulus liquid. The preferential distribution of zirconolite in anorthosite is explained in terms of expulsion of the intercumulus liquid by sintering or annealing of plagioclase. The crystallization of baddeleyite reflects the sharp increase of Zr in the trapped intercumulus liquid.

 Keywords zirconolite baddeleyite cumulate texture Laouni Hoggar Algeria