8

The dips of the strata do not support this interpretation. As more under-
ground exploration is done, more will be learned of the true dips of the
sediments, and the structure will become easier to decipher.

The rocks of the gold belt are traversed by a great many pre-mineral
fractures, many of which are occupied by quartz veins. The fractures are
relatively most plentiful in the Rainbow member. Most of the fractures
cut the strata at, roughly, right angles and their strikes range from north
15 to 60 degrees east. Another set of fractures cross the strike of the
beds diagonally and strike from north 60 degrees east to east. Others are
approximately parallel to the strata. Many of the fractures at right angles
to the strike of the strata contain no quartz, many hold quartz veins a frac-
tion of an inch to several feet wide. All the fractures diagonally crossing the
strata and so far as is known also all those that parallel the strata contain
quartz veins. The transverse and diagonal fractures are not faults. Those
roughly paralleling the strata are faults. The transverse and diagonal
fractures show marked relationships to the rocks traversed and these and
other premineral fractures will be discussed fully under types of mineral
deposits.

A number of post-mineral faults occur in the gold belt. Some of these
show considerable displacement, but most are small. The faults appear to
belong to different systems and were not all formed at the same time.

Faults of small displacement occur on one wall of some of the diagonal
veins. Locally these are called diagonal faults and appear to be the
earliest of the post-vein faults. Only a few such faults were seen and in
no case was the displacement measured. There is some crushed rock, how-
ever, between the fracture walls, showing that there was some displacement.
It would seem that the more persistent diagonal veins were the loci of early
post-vein movement of slight magnitude. In the Cariboo Gold Quartz mine
one of the diagonal faults is offset by a strike fault.

Several northerly striking faults that have offset the strata 1,200
feet or less horizontally cross the gold belt. These faults dip about 60
degrees east and in all cases the strata on the east side have been displaced
to the south. Four main faults of this type were recognized: the Rainbow
fault on which the strata are offset 400 feet, the Lowhee fault on which
the strata are offset about 1,200 feet, the Grouse fault on which the strata
are offset about 900 feet, and the Island Mountain fault encountered in
the workings of the Island Mountain mine and on which the offset has not
been measured or estimated, but which appears to be of smaller magnitude
than the others.

The Rainbow fault is crossed by the workings of the Cariboo Gold
Quartz mine and is better exposed than the others. It offsets veins and
locally also contains pieces of drag ore. These faults wherever they could be
studied are zones of broken rock 100 feet or so wide in which there is
one main locus of movement, a fault several feet wide, filled with gouge
and less finely crushed rock. The faults appear to branch but the branches
were not traced fully enough to demonstrate the exact fault pattern. The
faults may have been caused by settling, but the movement was not
eee downward along the dip but had also a component along the
strike.