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) 8-2
Porphyry deposits are commonly related to intrusive rocks and associated breccias but may also
include sedimentary, volcanic, igneous and metamorphic rocks. Tuffs or other extrusive volcanic
rocks may be associated with the deposits related to subvolcanic intrusions. These deposits
occur in high-level to subvolcanic felsic intrusive centres in cratons where multiple stages of
intrusive rock may be present.
Deposits vary in shape from an inverted cone to roughly cylindrical to highly irregular. They are
typically large, generally hundreds of metres across and tens to hundreds of metres in vertical
extent.
The age of mineralization is the same as the porphyry Mo deposits, Paleozoic to Tertiary. Tin
occurs principally in cassiterite with other ore minerals such as stannite, chalcopyrite, sphalerite
and galena. Indium can also occur within the sphalerite as observed at Mount Pleasant.
Common gangue minerals consist of pyrite, arsenopyrite, löllingite, topaz, fluorite, tourmaline,
muscovite, zinnwaldite and lepidolite. Mineralization is structurally controlled in stockworks within
crosscutting fractures and quartz veinlets or disseminated in hydrothermal breccia zones.
Mineralization is genetically related to felsic intrusions (i.e., granites), with ore minerals
concentrated in fracture stockworks, hydrothermal breccias and replacement zones.
Sericite-pyrite-tourmaline alteration is pervasive in Bolivian porphyry tin deposits where sericitic
alteration is bordered by weak propylitic alteration. Greisen alteration, consisting of quartz-topazsericite,
commonly occupies the central zones of deposits (i.e., Ardlethan, Yinyan). These zones
grade outward to quartz-sericite-chlorite alteration.
As with the porphyry Mo, tin deposits have a magmatic-hydrothermal origin with the same genetic
model (discussed above). However, in the case of tin deposition, the mixing of magmatic fluids
with meteoric water may result in the deposition of some tin and other metals in late-stage veins.
In exploring for tin porphyry deposits the host rocks may be anomalously high in Sn, Ag, W, Cu,
Zn, As, Pb, Rb, Li, F, and B close to the mineralized zones and in secondary dispersion halos in
overburden. Anomalous high concentrations of Sn, W, F, Cu, Pb and Zn have been found in
stream sediments. Deposits generally occur in related intrusions, which are geophysically
represented as magnetic lows although the contact aureole may be a magnetic high if pyrrhotite
or magnetite are present. Anomalous U, Th or K can produce a radiometric high in response to
the related intrusive rocks, alteration and mineralized zones.
Thibault & Associates Inc.
Applied Process Chemical Engineering