~122-

at th> contact of porphyry from which it has most probably been
derived there is nothing to suggest the probability of better.

ore being found elsewhere. The placer gold has been formed by

the weathering of the altered rock, which decomposed very

readily and the values found in the placer deposits also offer
some clue to the values likely to occur in the deposit.

To the east, at the head of the canyon, the deposit
is overlain by Tertiary lavas which are definitely younger than
the mineralization, and dip eastward so as to cut off any
possible extension at or near the surface in this direction.

The older volcanics are mainly grey and green, massive
andesites and tuffs. Quartz-feldspar porphyry in the canyon
section can be recognized mainly by the presence of rounded
quartz phenocrysts and less commonly feldspar phenocrysts. In
places neither is visible. Some dykes of similar and different
porphyries, all probably related, occur beyond the altered zone
where they are readily recognizable by their light grey or pink
colour. They are generally considerably altered.

The volcanics and porphyry in the deposit area are
altered to a light grey, very rotten material made up of quartz,
sericite, and mica, or in some places to a hard material made up
largely of quartz. The altered zone is exposed for over 1,500
feet in the canyon and southward, on the Ruby group and in other
exposures, to the showings on the Ark property on Back river one
mile above the bridge. Beyond this zone, especially on Bob ereek
and on Buck river below the creek, there are narrow, altered
zones where the green, unaltered volcanics can be seen grading
to the light grey, altered material, which borders dykes,
mineralized stringers, and fractures along which mineralizing
solutions moved. The extent of alteration is not always greatest
where the largest and most abundant stringers occur, but in general

the highly altered sections are probably the best mineralized.