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


The Belt sediments, in northern
Idaho and western Montana, have
been invaded by a number of small
stocks Of monzonite. syenite, granadi-
orite, and closely related rocks Those
in the Occur d'Alene district are pre-
s,lmed to be the arms of deep-lying
north extension Of the great quartz
monzonte batholith OF central Ida
no. About some of these arms there
are definite zones of contact meta
morphism.
Priohard Type Of Ore Deposits.
The Prichard type of ore deposits
inyades these zones, in few cases
to the very contact. The mineralogi-
cal character Of the deposits is like
that of the ordinary Prichard plus
contact metamorphic silcates. The
best example of these contact meta
morphic ore deposits is at the Gran
lite mine on the border of the Gem
monzonite area. Mr.. Ransome says
that 1.-THE association Of the ore min
erals with the metamorphic silicates
Is so close that the conclusion OF
their contemporaneou genesis Is I'M
questionable. The foregoing char
acterstics indicate that the ore of the
Granite mine was deposited shortly
after the Intrusion of the monzonite
and is phase of contact metamor-
phism." In proceeding eastward
away from the Gem monZonite there
Is gradual fading of the evidences
Of metamorphism. Garnet and green
biotite. are intergrown with the sui
phides in the Gem vein Green bio
lite and an asbestiform mineral oc-
cur with the sulphides in the Hercu-
les ore body. The ores Of the Granite
and Sixteen-to- One mines, IN the
contact zone, arc rich in sphalerite.
This mineral decreases In the Can
yon creek mines away from the mon
zonte area and upward in the veins.
Magnetic ard pyrrhotite are pres
ent near the contact, but seemingly
decrease and finally disappear entire
~ away from the IlpHZoHIte.
Wardner Type Of Ore.
After leaving Canyon creek district
by selection without reference to dis
lance from the mon2onite at Gem,
meteorological gradation may be
found TO what has been denominated
The Wardner type Of ore | suppose
this refers to an ore that consists Of
anartzite fragments, siderite, galena,
little vein quartz and practically no
uyrlte and sphalerite-the Bunker
Nil type Of my classification. The
magmatic hypothesis presumes that
the ore minerals in the contact meta
morphic deposits were derived from
the. monzonite and that as there Is an
apparent mineralogical graduation be-
tween all the ore deposits of the
Occur d'Alene district, it is reason
able to presume that they have all
been derived from the same source
and by the same process. their differ
ences being largely a function of dis
tance from the monzonite contact. 1t
IS supposed that when the solutions
issued from the monzonite, zinc sui
phide was at first deposited in equal
or even greater quantities than lead
sulphide. Siderite was driven to
considerable distance from the con-
tact. Thus the Prichard type must
owe It's characteristics to proximity
to the monzonite. 1t IS held that be-
cause ores in which pyrrhotite and
sphalerite are comparatively abund-
ant occur in the Pine creek pros
poets. the top of the hatholith may
not be very deeply buried What re-
gion. The fact that the Prichard
type Is confined to the Prichard form