The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1913-10-16


dominates In the supposed diffused
deposits at lower stratigraphic hori-
IONS and the lead content increases
higher; but perhaps l have made UNI
warranted use Of this case, particu-
larly as the exact situation Of the
eruptive is not known.
The Granite Mine.
At the Granite mine the ore occurs
in irregular masses which are prac-
tically confined to the Prichard sedi-
ments. The adjacent monzonite is
barren in appearance and contains
small aplitic and pegmatitic bikes
which. so far as ! could see in a sur
face examination, are absolutely bar
ren. "The commonly accepted theory
of the origin of aplite. is that It rep
resents the acidic remainder In a
granite or gauriz diorite magma ar
ter the. more basic elements have
crystalized. The aplite is forced up
| from below and fills previously form
ed cracks. which arc perhaps the re-
suit of cooling In the maA mass Of
granitoid rock" 1t seems to me that
there is here evidence that long af-
ter the Gem monZonite arm had cry
stabilized. at least in its upper por-
ton, the emanations from the deep
seated portions Of the magma did no.
bea. notable amounts of lead and
zinc At the Granite mine ] have
| seen small pockets of sphalerite In
the monzonite near the border: am
not certain whether they occur as in
illusions or have been deposited later
than the igneous rock. Streaks, sew
eral inches thick, of nearly solid ga
lena lie against wall Of monzonite.
strongly suspect that the ore depos-
It's We're in existence in some form
before the intrusion.
There is reason to consider 1t pos
sible that in time conclusive proof
may be secured that large part Of
the lead and zinc naturalization IN
the Occur d'Alene district autedatcd
the monaonte intrusion. The exac:
relation between the fault systems
and the intrusion has not been work
ed out. Immediately west Of the
southern portion of the Gem area
there is a badly faulted area contain
ing some comparatively old faults.
Unfortunately, it's relation to the
monzonite is obscured by a great
50, IA -, IN,,l Do,
TACT. The east side of the Gem area
seems more promising, When this
las been thoroughly studied 1t may
De found that much of the ore Is
sepetically connected With faults
hat are Older than monHonte. This
urinisc is warranted by the out
Tres of the various monzonite areas.
am inclined to the opinion now that
n my Wardner paper | put the mon
sonite intrusion too, far back /
,hought ! saw evidence of ii in GER
ain possible contact deposits, and in
he disseminated zinc-lead mnerall,
| zation making it older than the sec
| md system of faults These dcpos-
| is. however, may be due to an ear
| iier intrusion or to some other cause
| About all that Is positively known as
| % the age of the monzonitc is that
| it antedated the ninth system fault
| ing.
The Wardner district contains per-
| laps, the strongest evidence in sup
| )ort OF the magmatic hypothesis,
| When the four principal stages OF
lead deposition (the disseminated
zinc-lead naturalization and the Blue
Bird, Jersey and Bunker Hill stages),
are considered it will be seen that
there has been tendency to grad
/ lal elimination of the zinc and iron
change in the Canyon creek mines
has been attributed by Mr. Ransome
to the effect of increasing distance
from the monzonite and by me as
brought about by increasing distance
from the presumed source Of the
| minerals in diffused naturalization in
| the Prichard formation. In the
| Nardner district, however, it Is i
| function of time, not of depth. Un-
! Ter the mag1natic hypothesis 1t might
be explained as the result of n reced-
ing source. the solutions in each
stage starting at a much greater
lepth as the result of the progress
| i've soliditication of the magma I'M
fortunately. the same effect In so far
rs 1t is influenced by heat and pres
sure might be secured by the pro-
gressive decrease Of depth due to
lowering of the surface of the coun
try by erosion, so that it furnishes
10 real support to the magmatic n.y.
pothesis. Besides, there were tenn
porary returns to the zincy status.
The very latest ore naturalization in
the district has nearly as much zinc
as lead. The silver ratio increased to
the Jersey stage. but in the Bunker
Hill type dropped to normal, namely
la little less than half an ounce for
each per cent lead,
Mississippi Basin v. Occur d'Alens
Deposits.
| want to call attention to a curious
contrast in one particular between
the lead and zinc deposits of the Mis-
sissipp basin districts and those of
the Occur d'Alene. In the former