Hydrothermal garnierite; an occurrence at Bou Azzer, Morocco
Un gite hydrothermal de garnierites; l'exemple de Bou Azzer, Maroc
European Journal of Mineralogy (December 1993) 5 (6): 1205-1215
In the mining district of Bou Azzer, Morocco, garnierites containing variable proportions of Ni-kerolite and Ni-lizardite occur in a serpentinized ultramafic body of Precambrian age. These garnierites have 2.03-3.20 wt.% Co replacing Ni. Their delta (super 18) O value of +16.5 per mille and the random distribution of Ni and Mg cations in the octahedral sheet of kerolites indicate a T of formation > 25 degrees C. These results and the occurrence of garnierites in veins in association with Ni-arsenate ores show that these garnierites were formed during an early low-T hydrothermal event. All other garnierite occurrences have been attributed to lateritic weathering of ultramafic rocks.