Massive Sulphide Deposits in the Troilus Area, Chibougamau District: Are They Related to Volcanogenic Massive Sulphide Deposits?
Nathalie Légaré, Masters Thesis.
Masters thesis under the supervision of Dr. Jayanta Guha.
Project description
The purpose of this study is to characterize massive sulphide mineralization found in the Frotet-Troilus volcano-sedimentary belt (NTS sheets 32J/10 and 32J/15), approximately 100 km north of Chibougamau. This project is conducted in partnership with Géologie Québec, UQAC, SOQUEM INC. and several companies that are active in the area. This poster presents data collected during the summer of 1999 and outlines the controversial nature of these deposits.
Most of the mineral occurrences, with the exception of the Roméo Boisvert showing, are located in the south part of the Troilus area, along a NW-SE trending axis, which extends for 28 km over a width of 9 km, with showings regularly spaced every 5 km. Among these:
Lessard (Landore) : 1.2 Mt at 3.35% Zn, 1.96% Cu and 0.72 g/t Au;
Tortigny (Noranda) : 490,000 t at 6.21% Zn, 2.2% Cu, 61 g/t Ag and 0.3 g/t Au;
De Maurès (SOQUEM INC.) : 350,000 t at 7.84% Zn, 1.35% Cu and 22.31 g/t Ag;
Moléon (Coleraine) : 184,000 t at 3.4% Zn and 1.56% Cu;
Domergue (SOQUEM INC.) : 30,000 t at 5.51% Zn and 1.8% Cu ;
PK showing (Sirios) : 2.5% Zn, 0.8% Cu over 14.9 m;
Roméo Boisvert showing (SOQUEM INC.) : 6.73% Zn, 4.20% Cu and 27.8 g/t Ag over 1.0 m.
The mineralization is generally composed of massive PO and of SP. Most of the deposits and showings contain only one massive sulphide lens. However, the Lessard, Moléon and Domergue deposits consist of two closely-spaced lenses. The massive sulphides are hosted in various lithologies. For example, the Tortigny deposit and the PK showing are hosted in argillite-siltstone horizons, whereas the Moléon and Lessard deposits occur in a tuff sequence within an assemblage of basalts and mafic-ultramafic intrusions. As for the De Maurès and Domergue deposits and the Roméo Boisvert showing, the mineralization is found along lithological contacts. The De Maurès deposit is hosted within tuffs and basalts, whereas the Domergue deposit occurs within a pyroxenite and a gabbro. The Roméo Boisvert showing occurs at the contact between a basalt and a gabbro. Massive sulphide occurrences in the area are weakly deformed, except for the Tortigny deposit, which occupies a fold hinge.
The nature of massive sulphides in the Troilus area is poorly defined. When trying to compare these occurrences with volcanogenic-type massive sulphides, it is difficult to identify alteration pipes that could have served as conduits for the mineralizing fluids. Furthermore, the presence of exhalative horizons has not been clearly established. Silicified horizons are observed in the vicinity of the deposits, however they are not extensive, which does not suggest an exhalative origin. Some of these elements could suggest a lode-type origin for these mineral occurrences. However, the possibility of a combination of different types of mineralization should not be excluded, and may lead to a new exploration approach in the area.
Question or commentary contact me: nath_legare@uqac.ca.
