New gold targets in the Chibougamau area
Most Cu-Au deposits in the Chibougamau mining camp
are hosted in NW-SE shear zones (mine shear) within the meta-anorthosite
along the northern DLC. These zones are interpreted as synvolcanic
structures that were reactivated by regional deformation (Kirkham
et al., 1998). From 1954 to the end of 1997, eleven (11) ore deposits
were mined in NW-SE shear zones, for a total production of 31.7
million short tons of ore at a grade of 1.76% Cu and 2.26 g/t Au.
Historically, mines in the lac Doré and lac Chibougamau
area have yielded a total production of 46.9 million short tons
of ore at a grade of 1.74% Cu and 2.19 g/t Au, amounting to a little
over 1.6 billion pounds of copper and 3.1 million ounces of gold
(PDF Format, 65 kb).
Similarly, there are many other examples of gold
deposits associated with granitoid intrusions in the Abitibi geological
Subprovince. Among these, the Bourlamaque batholith in the Val-d’Or
area hosts several gold deposits along its margins. Furthermore,
the Belmoral mine (1,710,102 t at 6.46 g/t Au) is hosted in a shear
zone within the Bourlamaque batholith, in a setting similar to what
is observed in the western part of the Chibougamau Pluton.
In addition, late orogenic gold-bearing quartz
veins in the Rouyn-Noranda mining district are largely hosted in
Archean tonalitic plutons of the Blake River Group. For example,
the Silidor mine (2.95 million tonnes at 5.1 g/t Au) is a 900-m-long
ore zone oriented N330º/55ºE, with a vertical extension
of 900 m and an average width of 3.5 m. It is enclosed in a strongly
hematized trondhjemite of the Powell Pluton. The Silidor deposit
is the result of several vein-filling episodes, which took place
throughout the evolution of a fault network with normal or reverse
movements (Carrier et al., 2000). NW to NNW-oriented lode gold deposits
in the Powell Pluton therefore appear to be similar in many ways
to NW to NNW structures in the western part of the Chibougamau Pluton.