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part of the exposures; away from this part, both on the surface
and at depth, the zones have fewer and less woll-defined fractures
or the fractures are more scattered. The fractures were formed
by tension and were open when mineralized. In a fow places there
is shearing along the zones, and much of this was developed

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during and after ore deposition. Most of the depos
southwestern slope and near Simpson creek, the silver-lead-zinc-
gold deposits of Glacier gulch and the silver-leead deposits of
the Silver Lake and Silver Creek groups and probably others in
the Toboggan Creek section are in this type of fracture zone.

The deposit on the Silver Creek group parallels Tobogran creek
instead of striking toward the peak and indicates saat locally
there are exceptions in regard to strike.

In goneral the deposits of this type are found on the
outer slope of the mountains, that is, on spurs rather than in
valleys or cirques. Many are near the remants of the sediment-
ary shell that once covered the mountain. In fact, it appears
that with few exceptions the deposits occur in a zone a few
hundred feet thick that originally underlay the sediments.

Where but little crosion has taken place since the zemoval of
these rocks the deposits are still largely intact, but with
inerease in extent of erosion there is a decrease in number and
size of deposits.

Localization of the mineral deposits in a zone below
the sediments probably was due in part to more intense fracturing
there and it may be that the sediments acted as a berricr to
further progress outward of the mineralizing solutions. This
appears to be shovm by the searcity of important mineral deposits
within the sediments. If this be true the best mineralized
material would be expected immediately below the sediments and

beyond this it would tend to become poorer.

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