The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1906-10-21
MORE ON ElY'S
ORE FORMATION
Extract From Report That
Deals With Limestone Fringes
of Porphyry Intrusion.
RICH ORE BODIES IN LIME
OPINION OF HOW MINERAL WAS
DEPOSITED.

The description of the copper-bearing
porphyries of the Ely camp and the
manner in which the enrichment OF the
material occurred. by Colonel E. A.
Wall. and published on the eth of the
present month, has been read with
great deal of interest, particularly by
mining engineers and men Of the camp
owning properties Since then regret
has been expressed that he did not go
deeper into the subject and express his
opinion on the country thanking the
porphyry deposits. Colonel Wall did
rot spend much time in the camp and
was. therefore, unable to go into great
detail, fact that he regretted as much
as any one. He was preparing for
trip east when his article was prepared,
and he did not even find time to make
a cross-section sketch, explanatory of
the manner i'm which the country had
been disturbed by the porphyry intru-
sion. He wanted to do that, and he
wanted to say something about the
marginal possibilities of the main de-
posit. but he WIS forced to omit it.
r. s. Pheby. the Ely banker. now in
the city. who with others owns the
Nevada Northern group of claims two
miles westerly from the. town of Ely,
and north of the chairman, has an ex-
pert report upon his property that deals
i'm some detail with the geological con-
ditions that people are inQuiring about
and, with his permission, The Herald
quotes from that expert report as fol-
lows:
Formation of Ore Bodies.
Two general processes have operated
10 form the ores on the north side of
Robinson canyon: "a metasomatic al
a..
10 naturalization deposition of chal-
cOpyrite. a sulphide of copper and
from, and co oxidation of such py-
rite masses, and its attendant phenOm-
ena Of transportation Of the copper con-
tent by percolating waters and the
deposition of such copper 20 enrich
other and lower portions of the same
ore body. Most replacement ore bodies
Invariably SHOW these two processes TO
have been al work and to be still in
operation. and by this wonderful work
of nature. many low grade pyritie ore
hodies are gradually transformed into
bodies of commercial ore. Attendant
upon the deposition of the ore bodies.
was the silicif1cation of some consid-
cradle limestone. generally along the
foot wall or lower side.
Originally the ore bodies were COM
posed of lean iron pyrite and some chal-
copyrite, and by teaching and concen-
tration of large mass Of pyrite, leav-
ing as residual the oxidized iron, the
secOndarily enriched ore bodies are
formed: changed by superficial altera-
ton into carbonates in their upper por-
7lon and relatively enriched in the I'M
derlying portions by black suphides
with additional gold and silver values.
However. there is sufficient evidence of
copper in the present. surface groupings
to make il certain these bodies carried
copper. Eventually these sulphide ore
bodies became OXidiZed- Z nd descend
ing surface waters leached the copper
contained and redeposlted it at greater
Cepths. therefore the leaving, the pres
cnt iron caps or gossars.
Ore in Ruth Limestone
THE most promising gossans of
rusty brown limonite seem to be re-
stricted TO zone several hundred feet
wide, where the limestOnes have been
subjected TO considerable assuring and
intrusion by irregular masses of igne-
Gus rock. taking the form of stills or
dykes The ore bodies seem to be re-
.stricted TO the thick. massive Ruth
limestone to The north of Robinson can
yon, the canyon proba bly, being the re-
suit of erosion along an extensive fault
plane.
Surface study shows that these ore
bodies are not altogether confined to
single horizon i'm the limestone Just
above the intrusive, but have formed at
various levels TO the top of the divide.
They are something distinct from the
poryphyTy ore bodies that are of such
magnitude and so well known in the
Ely district. However, .hey resemble
very strongly the ore bodies of Bis
bee. Clifton, Morenci and Globe. No
work has been done TO prove them 9
extensive as the ore bodies of these
great camps just enumerated, but in
character of deposition and occurrence
they are Identical. being a replacement
Of the limestone near an intrusive dyke
Particularly are they like the ore bodies
of Bisbee.
Ores Follow Bedding Planes.
''The very irregular tabular or len
ticular masses of ore follow assures and
bedding planes in the enclosing lime
stones. The assuring and fracturing of
-le limestone is observed to be a factor
N the naturalization, and the lime
stones so assured and fractured seem
10 have permitted the more ready cir
citation of mneralizatiing heated
aquas solutions. One ore body on the
1lathe claim of the Nevada Northern
Copper company distinctly shows all
the stratification- and. peculiar curly |
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