NI 43-101 Independent Technical Report Mount ... - Adex Mining Inc.

NI 43-101 Independent Technical Report Rev 02 January 22 nd , 2010
Mount Pleasant North Zone Preliminary Assessment (Project 6526-03) 7-2
Figure 7-2: Local Geology of Mount Pleasant Property
(Figure Credit: Watts, Griffis & McOuat)
Mount Pleasant represents the volcanic remnants with both vent and conduit fillings of a mineralrich
volcanic eruptive centre located along the southwest margin of the Mount Pleasant Caldera
(see X2, Adex Mining Inc., 1995). This eruptive centre has a marked topographic expression
reaching 230 m above the valley floor.
At Mount Pleasant, the caldera is comprised of Piskahegan Group rocks of Late Devonian age
consisting of three ash flow layers of rhyolitic pyroclastic rocks referred to as the Quartz-Feldspar
Porphyry that are separated by two discontinuous units of sedimentary breccia (up to 100 m
thick) that forms the western boundary of the caldera, a feldspar porphyry and metasedimentary
rocks of interbedded red conglomerate, sandstone and shale (Sinclair et al, 2005; Billiton Canada
Ltd., 1985b). These ash flow tuffs of the Piskahegan Group probably originated from the
numerous vents in the caldera. All rocks within the caldera generally dip about 10° to 15° to the
northwest except along the margin of the Mount Pleasant Caldera where they dip at 15° to 50°
toward the centre of the caldera (Sinclair et at, 1988).
The caldera rocks have been intruded by a line of inverted cone-shaped cupolas of granitic rocks
and associated breccias (collectively named the “Mount Pleasant Porphyry”) that outcrop at the
North Zone, Fire Tower Zone and within an intermediate Saddle Zone that does not reach
surface. It should be noted that little information has been provided on the “Little Mount Pleasant”
cupola that occurs at depth to the south of the Fire Tower Zone. At the Fire Tower and North
Zones, crosscutting breccias and associated intrusive rocks form irregular, roughly vertical pipe-
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