| Summary: | A gold copper deposit in Archean mafic volcanic rocks,
near the eastern limit of the Abitibi Greenstone belt about
2 km north of the Grenville Front, and 65 km southwest of
Chibougamau, Quebec, is described with reference to major
mineralogy, textures and alteration. Host rocks consist of
an intrusive subvolcanic gabbro sill and mafic and felsic
volcanic rocks formed in a volcano-sedimentary environment*
This sequence was intruded by felsic and diabase dykes.
Mineralization consists of native gold and chalcopyrite in
brecciated quartz veins, formed as fracture-fillings, located
in three subparallel shear zones cutting the gabbro, mafic
and felsic volcanic rocks. Chalcopyrite, pyrite, pyrrhotite
and minor sphalerite are found in breccia interstices and in
disseminations near the veins but are not spatially related
to the gold mineralization. The gold is contained in quartz
and albite. Textures show it was the last mineral to be
deposited in the veins.
A mineral identified as anhydrite is found in the
'main' shear and the mafic volcanic rock unit of the mine
sequence. As anhydrite has not been found elsewhere in the
region it may be possible to use its presence as a
stratigraphie indicator.
A hydrothermal lateral secretion origin is postulated
for the deposit. Basic, reducing, carbonate and H2S-bearing
fluids have the capability to transport the mineralization
of the deposit and to produce the alteration noted in the
host rocks. The deposition of the gold mineralization took
place during late stages of, or after, regional metamorphism.
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