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Subject: Gold Potential of the Broulan Reef Property (Posted on Jun 22, 2009 at 07:11PM)
Summary of the Geologic Setting of the Bruce Channel Gold Deposit
The Bruce Channel Gold Deposit (BCGD) is a shear hosted ore body which lies within the Archean age Balmer formation and is now known to represent the down dip continuation of the historic Cochenour ore body. The Cochenour deposit was found in outcrop in the western portion of the Red Lake district during the initial phase of prospecting /exploration in the late 1920s The host shear zone is reported to strike N-S and dip 70o to the west.
The Balmer formation outcrops to a limited extent in the Cochenour mine area where strong alteration and local structural complexity make detailed mapping difficult. The Balmer formation rocks are dominantly massive mafic flows and largely lack good marker units. The BCGD lies under the waters of the Bruce Channel of Red Lake. No surface mapping data exists. 2 Drill data show that the Bruce Channel Formation, a series of younger sedimentary and volcanic rocks (including abundant magnetite iron formations), covers the Balmer at the BCGD and Broulan, further masking the geometry of the host rocks and making surface geophysical interpretations impossible. Reliable stratigraphic marker units are rare but one package has been identified in several drill holes and gives consistent east-west strikes and near vertical dip of the Balmer in the BCGD-Cochenour-Broulan area. This geometry is consistent with mapping in Balmer further east in the Campbell Dickenson area. N-S to NNE striking, talcose, ultramafic volcanic rocks within the Balmer formation in the BCGD-Cochenour area occur within the highly sheared East Bay Deformation Zone. It is unlikely that the apparent strike of these units results from anything but structural and is the result of smearing in the shear zone and thus is completely unrelated to any pre-shear-deformation geometry. These highly deformed and altered ultra mafic rocks are thought to be very important for nearby ore deposition due to their high ductility contrast with surrounding units. Highly deformed and altered ultra mafic rocks have been intercepted within strong shear zones at Broulan.
The host shear zone at the BCGD intersects the largely east-west striking stratigraphy of the Balmer formation at approximately 90 o. A very similar geometry is likely present at the Broulan property.
The main zone of the BCGD has been variously estimated to contain from 4 million to over 10 million ounces of gold at grades of around an ounce per ton. It now seems certain that production from the BCGD will easily surpass that of the historic Cochenour mine and will do so with higher head grades and with much greater continuity of the mineralization. It might be time to refer to the Cochenour deposit as the up dip extension of the spectacular BCGD rather than the other way around. The premium price paid by Gold Corp to Gold Eagle in 2008 for the BCGD makes this point as clear as possible.