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COPPER SILVER VEINS OF TELKWA DISTRICT. 361

Hematite,

Magnetite,
nt,
Chalcopyrite.

Chalcocite,
IV.) Covellite,
Calcite.

The sequence in each separate group is not to be inferred from
this arrangement for in each of the four periods some or all of
the minerals were deposited simultaneously, or the order alter-
nated from one sequence to the other. This is particularly true
of the second group in which the order of the bornite and chal-
cocite is reversed from bornite-chalcocite to chalcocite-bornite,
and it is clear in other places that both minerals were being de-
posited simultaneously. The relations of the chalcopyrite and
bornite in this group indicate a contemporaneous deposition for
some, and a later deposition for other portions of it.

Genesis.—The processes which brought about this complicated
and apparently unusual sequence of mineralization are believed
to have taken place as follows:

After the intrusion of the granodiorite stock, the adjoining
tuffs suffered an intense thermal and hydrothermal alteration,
producing a metamorphic zone extending half a mile or more
away from the contact in all directions. This metamorphism
was characterized by silicification, biotitization, with the dissemina-
tion of epidote, copper and iron sulphides, and a little silver. In
certain porous beds a large amount of hornblende was produced,
with epidote, magnetite and hematite. In these beds the min-
eralizing solutions and vapors were able to travel faster and thus
produce a more intense alteration and to develop it farther from
the contact than in the less porous beds. The first and hottest
heat waves to pass off from the intrusion produced the meta-
morphic zone, and seemed to have the effect of closing any fissures
which may have existed, for there were no veins of any kind
seen in this zone. Beyond this, many fissures remained open,
forming channels along which the solutions flowed and deposited
the minerals which now form the richer veins of the district.