Environmental Impact Assessment Of The Mountain Pine Ridge ...

Tectonics
The granite batholith on which the mining site is located consists of an uplifted fault block of precretaceous
basement, consisting of a synclinorium trending east-northeast and plunging to the west
about 10 degrees (Bateson & Hall, 1977). The site lies some 5 Km southeast of the still-active
Northern Boundary Fault, and is divided to the east by the 6-kilometer deep Cooma-Cairn dip-slip
fault; to the north and south by at least two large perpendicular faults (the latter three most likely
originating in the Paleozoic); and thereafter by numerous lesser faults and joints (of unknown, but
probably more recent age). Displacements of some faults are shown by offset quartz veins, which
indicate the area to have been tectonically affected after vein formation (Holland, 2002). The larger
fault systems along with two earthquake epicenters recorded between 1900 and 1999 lying
approximately 6 – 8 kilometers southwest and northwest (respectively) from the mining site were
mapped by Cornic (2003).
Illustration 19 shows the mining site itself to be positioned centrally among the latter three larger
above-referenced faults, at approximately 2.5 Km distance. The coarse grained granite of the
Mountain Pine Ridge exhibits microfractures and fault displacements that are likely the result of the
granites position within a zone of abundant faulting, but mineral alteration within the infilled
microfractures were taken by Dawe (1984) to be indicative of hydrothermal alteration. Inspections
by other researchers (e.g. Holland 2002) indicate some fractures intermittently to be infilled with
quartz at intervals ranging from a few centimeters to more than a meter, which also governs
material suitability for mining and processing into finished products.
Dawe (1984) and later Kwon (2005) surmised
the mining site were probably tectonic valleys
(owing to their alignments), comprised of
structural joints, fractures or dislocation zones
that have been secondarily influenced by
groundwater weathering along the granite
surface, causing soils and overburden to deepen
on side slopes (see Illustration 20), and area
creek flows to persist throughout the dry season
that creek alignments immediately adjacent to.
Stratigraphy
Soil Structure & Classification
ILLUSTRATION 20: GROUNDWATER FLOW &
WEATHERING ALONG SIDESLOPES
King et al 1992 report the soils of the project site to largely consist of Stopper suite Pinol subsuite
soils, which consist of the colluvial and hillwash soils formed on the granites off the Mountain Pine
Ridge. King et al further report there is considerable variation in the Pinol subsuite, with the main
soils of slopes on the more melanocratic granites characterized by bright red and yellow colors and
moderate depth with a very diffuse gradation to the underlying weathering granite; and the topsoil of
stable sites being either shallow and moderately dark, or lacking melanized topsoil altogether (see
Illustration 21: Upper left photo: deeper soils of the side slope at the mining site; Upper right photo:
shallow soil of the top slope at the mining site).
The Mountain Pine Ridge Granite Quarry EIA / Ecoworks Page 36 of 167