Abstract

Massive monazite occurs in a zoned deposit in the Wollaston Lake fold belt, Kulyk Lake area, northern Saskatchewan. The deposit is enclosed by pegmatitic, graphic, and aplitic granite, which are slightly bleached adjacent to the contact. Ilmeno-hematite and hematite (in part after magnetite), located adjacent to the silicate rocks, are followed inward by massive monazite and then minor concentrations of apatite. Monazite has a constant chemical composition: the average microprobe analysis is CaO—0.5, La2O3—15.1, Ce2O3—36.1, Pr2O3—4.9, Nd2O3—10.1, ThO2—4.3, P2O5—27.8; total, 98.8%. Monazite grains in a small segregation in granitic gneisses have variable thoria contents. Apatite in the deposit contains about 0.2% total rare earths. The oxide–monazite–apatite deposit probably precipitated from an aqueous phase generated during crystallization of a water-rich granitic liquid. The monazite deposit and enclosing granitic rocks may have been generated during anatexis of a metasedimentary unit containing abundant monazite and Fe–Ti oxides.

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