The Salt Lake tribune. [volume] (Salt Lake City, Utah) 1890-current, 1907-03-11

copper ore OF the Ruth mine-porphyry
lmpregnated with cha1cocite and pyrite
part To secondary enrichment by down
/ ward teaching from the zone OF oNidIza-
ton. The fact that the oxidized zone
might easily be robbed OF it's copper ore
by the teaching action OF sulphide OF iron
! was experimentally verified by placing
! n mixture OF puverized chalcocite and
| porphyry I'm n burcttc and causing n ten
! per cent solution Of ferrous sulphate TO
pass through 1t in presence OF the atno-
! sphere. The chslcocite was taken into
solution and passed from the burette as
! copper sulphate CuSOl4 at n fairly rapid
rate. While this secondary enrichment
Of the porphyry below the zone of oXl-
| dalton is unquestionable, two important
and significant facts remain 10 he noted,
! The first of these Is that the products
OF this enrichment are not localized at
any particular horizon In the porphyry,
so far as the development OF the mine hns
get gone The copper values are by no
means evenly. distributed In the ore
richer ground Is apparently rather de
termined by freedom OF flow OF descend
ing solutions, that is, by local structural
conditions In the porphyrv. than by any
horizontal control such MS the present
level of the ground water,
THE only primary deposits OF copper
are limited bodies of chslcopvrite init
mately associated with garnet rock. or
with garnet and quartz, These primary
ores occur in two distinct situations One
OF these is at the contact OF intrusive
rocks, particularly the monZonte and
monzonitc porphyry with the carbonifer-
Gus imestones. Here they are clearly
roferable to a process Of contact meta
morphlsm. BY this Is meant not merely
thermal metamorphism, but reactionary
metamorphism. whereby solutions bearing
silica and iron from the intrusive mass re-
act upon the lime carbonate and give
rlsc to the lime Iron slicate. garnet.
These same solutions appear to have
brought with them the materials neces-
sary for the deposition OF the chalcopy-
rite, and sometimes there was an excess
of silica which was precipitated as quartz,
The other situation In which primary
copper ores have been detected is in the
quartz blout, and here again 1t is init
mately associated with garnet. From
considerations set forth I'm previous pages,
it appears very probable. indeed, If not
n demonstrated fact. that the quartz blout
is largely the result of sllfcation OF the
limestone chiefly ON the periphery OF the
copper bearing porphyry, but also partly
alonE assures in the limestone In the vi
cInity of the porphyry. AT the surface.
and often for considerable depths below
the surface, these ores are now In the
form OF the carbonates. malachitc and
azurite. But these carbonates are re-
Garded the result OF tho alteration OF
in stu. In other localities,
at the Morris shaft, near
Pilot Knob and at pit near the road
between Copper Flat and Pilot Knob. The l
garnet with pyrite and chalcopyrlte. In |
the Copper Flat mine. on the 300-foot /
level. there Is an extensive body OF So
called dixie of garnet rock with nests /
OF pyrite and chacopyrite. The garnet .
rock Is for the most part thoroughly .
decomposed To greenish or brownish /
which, when moist. has a cheesy /
and on drying OIL the dump
slacks in the air All gradations may /
be observed between the perfectly fresh /
garnet rock and the decomposcd material /
ut thus appears that the only traces |
o! primary copper ores in the district |
are in the form OF chalcopyrte asso-
clated with garnet, and that certain of |
these occur In the quartz blout either az
the original chalcopyrite or altered to car
Donates, The hypothesis may be favor
ably entertained that the secondary cop
per ore of the Ruth mine has been derived
form the downward teaching OF copper
from bodies and disseminated particles of
in the course OF superficial
OF the blout in which they were
originally deposited. There are at pres
ent vast bodies of blout at the surface
above the Ruth mine but
these are only remnants. The greater
part OF the blout has been removed by
erosion. The product OF this teaching was
deposited as chalconcite In the porphyry
at a time when the water level was
much higher than at present. And finally
when In consequence OF the suhsidence of
he ground water to lower levels the
zone OF oxidation extended into the por-
ohyry. this chalcoCite was in turn taken
nto solution and redeposited as chalco-
lite at still lower levels"