The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1913-10-09

irregularly distributed in the sedi-
mentary than in the igneous rocks as
they were only precipitated when and
where conditions were unusually fav-
orable. In this connection 1t must be
noted that they are more likely to oc-
cur in the older than in the younger
sedimentary rocks because the former
were more directly and extensively de-
rived by the erosion of igneous rocks
The Belt and the early Cambrian sea-
iments were especially favored in this
regard, but even in the Idaho region.
conditions favorable TO the formation
of the diffused deposits may have
been limited to very small part OF
fhe AIgonkian time and to relative
ly small portion Of the Belt water
body.
Since early Tertiary time some mil
lions of tons Of lead and zinc have
been eroded from the Occur dAlene
district. Rather elaborate tests made
In connection with some debris litiga-
ton have shown that exceedingly
small quantities of lead have remain
ed in the alluvium of the Occur
d'Alene river. and that there Is prac-
ticaliy no lead in solution in the river
water, that Is, scarcely any detectible
by ordinary means. There is under
ground evidence that very little Of
the lead and zinc have gone to form
new deposits In the district; It Is
therefore, incontrovertible that the
Occur d'Alene river has carried mil
lions OF tons of these metals out Of
The district. Soane Of them may have
found temporary resting place on
the bottom of Occur d'Alene lake, but
all must ultimately reach the Pacific
ocean, where they may be precipitated
as diffused deposits in the sediments.
II, instead Of being derived from a
small number of highly concentrated
deposits, the minerals came from the
disintegration of many cubic miles Of
lead and zinc bearing igneous rock,
the result so far as the lead and zinc
content of'the marine sediment Is con-
cerned. might be the same
Genesis Of Lead Zinc Silver Deposits.
Two principal working hypothesis as
to the genesis of the lead-zinc- silver
deposits of the Occur d'Alene district
are before the public One is modi-
fcation of what would be termed by
H. r. Balm, the sedigenetic hypothe-
sis, and the other is the magmatic hy-
pothesis. Both refer the ultimate
source of the metals to igneous rocks.
The former implies that the lead
zinc and associated silver minerals be-
came diffused in certain bands Of the
preceding pages and subsequently con-
centrated into the present commercial
ore deposits as suggested in my pa
per on the Wardner district The lat
ter hypothesis implies that these min
erals remained below the Belt rocks
until comparatively late period when
they were expelled from the deep
seated portions of the magma, which
|crystallized into quartz monzonite and
related rocks, and were deposited In
the Belt rocks. F. L. Ransome is the
chief exponent of this magmatic the
DRY. Others have supported it IN oral
communications. Another geologist
has advanced the theory that the ore
deposits were derived by downward
teaching from diffused minerals either
in basalt cover, long since removed
from the Occur d'Alene, or in the
higher portions of the Belt rocks
themselves. AS this hypothesis has
not been formulated publicly, and as it
is so strongly opposed by evidences
that the mineral bearing solutions
have moved upward instead of down
ward, | will not discuss it further
Prjchard Type Of Lead.zinc Deposits.
The Prichard areas in the Occur
dAlene district are characterized by
what may be called the Prichard type
of lead-zinc ore deposits. In this
type. zinc sulphide, presumably spinal
critic. Is abundant, and the silver ratio
is very low. The blende varies from
a pale yellowish gray to dark brown
color In some veins there is rather
intimate mixture of the blende and
galena but usually they are fairly well
separated In one mine in the valley
of the North Fork of the Occur
d'Alene river which have visited, the
zincblende Is often in masses l to \
feet thick and feet long. Elsewhere
In this mine, blende and galena with
some quartz and calcite are interwov.
en-. In other places the galena tends
to follow seams and may be later than
the blende. There are small quanti-
ties of chalcopyrite and pyrite, but nc
siderite. There are said to be to II
ounces silver per ton to 70 per cent
lead In the lead shipments and prac-
tically no silver In the zinc ship
ments. specimen Of blende assayed
Sis per cent zinc. 49, per cent iron and
no silver. At the Surprise mine in the
valley of the east fork Of Pine creek,
lead concentrate carries about So per
cent lead and IS ounces silver per ton,
and the zinc concentrate about "A per
cent zinc and ounces silver per ton
Mr.. Ransome states that at the Bear
Top mine the ore consists Of galena,
acsnciata with Sphalerite pVritp