Deseret evening news. [volume] (Great Salt Lake City [Utah]) 1867-1920, 1905-12-02
Governments
T0N0PAH REPORT.
Geological Survey Makes an Ex-
hauStive Examination Of
The Nevada Camp.
HOT WATER CAUSED VEINS.
District Resembles the Comstock Lode
And the Mines Around DE La
Mar, Idaho.

The United States Geological survey
gives out the following report upon the
formation OF the Tonopah Mining dis
trct In Nevada, and also OF the econ
omlc value Of its deposits. 1t is In
terestlng to note that Geologist Spur
who made the examination OF the dis
tnct. finds very close resemblance
between It and the deposits OF the Com
stock lode and the De La Mar, Idaho.
mines.
The report. though lengthy, is OF 80
much interest TO the mining public OF
Salt Lake that It is given In full.
The geological problem presented IN
this district could have been solved
only by a trained photographer, since
the igneous rocks that carry the vein
deposits have been largely covered by
practically barren flows Of more recent
eruptlves. The very careful and thor
ough study OF the district which Mr..
spur has made can hardly fail to be
OF great practical value to the miner,
as well as OF scientific interest to the
student OF ore deposits. The value and
interest OF the text are enhanced by the
addition OF rs Illustrations, which In
clude Topographic and geologic maps
tsome OF them in colorsl, diagrams,
steorograms, plans OF veins and faults,
geologic sections and eros sections,
and Photographic Views of Characters
tie landscape features.
The rocks OF the mining district are
all Of immediate volcanic origin, with
the exception of series OF water-laid
tufts. which represent the accumula-
10 lot A4 Naf-
tlary age, probably Miocene- Pliocene.
The first eruptives Of this volcanic ep-
och. as displayed at Tonopah, were an
destites. Two andestites have been dis
tinguished--the younger or earlier an
destlte and the later andestite which
Is slightly more basic than the earlier
undestlte Subsequently eruptions OF
rhyollte and Of dacite occurred at In
tervals for q long time and produced
several OF the formations mapped,
which include tufts and flows.
The structure Is so complicated that
no general cross sections have been
made Some interesting Information
on faultlng has, however been obtain
ed, chiefly from mine workings
The most important mineral veins oc-
cur In the early andeslte, and do not
extend into the everything rocks. The
hot ascending waters Immediately after
the earlier andeslte eruption, The pri-
mary ores have a gangue OF quartz, adj
uarla, and some serlcite and carbon
, ates and contain silver sulphides-such
as argentte, polybasite, and stephanite
silver selenide, gold IN yet undeter-
mined form. chalcOpyrite, pyrlte, and
some galena and blende The depth Of
| oxidation Is irregular. In the ore OF
| TIC oXidlzed zone no important changes
| In the amount OF gold or silver, as COM
| pared with the primary ore, have taken
| place. The ore near the surface Is not
| truly oXdized mixture OF original sui
| phides (and selenides), together with
| secondary sulphides. chlorides and OK
ides Secondary sulphldes include ar
| gentle and pyrargyrte,
| a series OF veins Of small import ance
| commercially within the Tonopah dis
| trlct. was formed after the eruption OF
one Of the members OF the rhyoliie- da-
| cite series--the Tonopah rhyollte-dacte.
| These veins may be large, but are usu-
| ally OF low grade or barren. They fire.
| quently contain a greater proportion OF
| gold than the earlier andestite veins,
and have other distinguishing charac-
'eristics.
A series Of veins Of still less impor-
| lance was formed after the eruption OF
one Of the later members OF the rhyo-
lite dacite series--a slllceous rhyolite
which makes up some OF the hills near
Tonopah. One OF these. Mount Ararat
| a denuded volcanic neck is traverset
by assure veins that carry very little
| values.
Part of the earlier andestlte is pro
foundly altered The maximum effec
Of the waters which caused these alter.
ations was the formation of the minera
veins along their circulation channels
Tho discussion Of these processes u
| followed by the detailed study of an
alyses OF typical specimens, The con
/ clusion Is drawn that the mineralizn,
waters were charged with an excess
OF silica, and probably OF potash, to
gether with silver gold, antimony, ar
senlc, copper lead, zinc, and selenfum
| that they also contained carbOnlc act
and sulphur, with some chlorine an
huorne, but that they were noticeabl
deficient In iron.
The alteration OF the later andestit
by thermal waters Is also discussed II
comparison Of analyses and by micro
SCOPE studies II Is concluded that tn
waters which produced the alteratio
were highly charged with carbonic aci
and sulphureted hydrogen, and contain
ed magnesla, iron, and lime,
The two theories Of the origin OF he
springs---atmosp herlc and magmatic-
are discussed by Mr.. Spur IN connet
ton with the Tonopah phenomena. IN
meaning OF the nature of the metals
the Tonopah veins Is also dlscuse,
The conclusion f. reached that the wa
. ters which produced the veins wei
, largely given of from the congealin
. lava below.