The Central Nevadan. [volume] (Battle Mountain, Nev.) 1885-1907, 1901-11-07

solution in percolating waters This
stage won d therefore be the first or for
nation one for fssure veins. This sec
ond stage would include the commence
ment OF the final elevation of the deeply
subsidized strata until approaching the
surface when the third stage would be-
gin.
THIRD STAGE.
OXIDATION HYpRATIoN AND DIsINTEGRA-
During and even preceding the sec
ond stage the chemical action taking
place in the strata would be reducing
one as air would be excluded and organ
Ic matter would be largely present es-
pecially during the carboniferous and
subsequent periods with which we are
chiefly concerned. While emerging
above or near the valleys and plains and
low river and creek beds and some of
the depression OF this country having
been once seas and lakes as Is shown by
the salt and boracic acid deposits now in
existence in many places. The rocks
and enclosed ore deposits would become
subject to another series of changes
mainly and il not entirely oxidizing in
their nature and generally tending to
their disruption and decay but in the
case OF ore deposits often causing par
tial concentration and enrichment. The
subaerial phenomena or those with which
man should be most familiar but their
causes although far reaching in economic
geology have only of later years began to
be studied and their teaching applied.
Their presence is largely determined by
climate and topography and will always
be most evident in warm and dry eli
mate and an elevated region and most
feeble in cold and dry country. Ii this
were warm and moist climate, gold
would predominate but as it is warm and
dry. silver predominates and accounts
for copper and galena ore being present
and iron being scarce. The watery va
por from the 1owlands and depression
condensed into rain and snow and
charged with the carbonic acid of the
atmosphere and with the organic acids
Of the soil through which it percolates
peryneates and penetrates most il not all
rocks with hydrating and oxdizing ac-
ton and also as solvent of many min
erals and ores By this circulation which
reaches to great depths and always to
the permanent ground water level rocks
are aisentegraded, metallic and other
minerals dissolved and the solutions
reach by gravity the underlying rocks
where they create new deposits differing
in composition from the original ones
and often forming below the surface
specially enriched zones Of limited depth.
These zones in ore deposits generally
carry native metals, carbonates and OK
ides derived from original sulphides ar
senides, tellurides and selemides. Their
situation is specially determined by the
position OF the ore body and the charac-
ter OF surrounding country rock and
within large lodes pay shoots are fro-
quently defined by them. The effects
OF this hydrating and oxidizing circula-
tion-which may be designated as the
metoric-is most notable in ore deposits
containing limestone and other carbonic
acid aid in the disintegration of quartz
and all silicates. In the Shoshone and
Toiyabe range where the meteoric cir
culatioD is spec tally active. Great If un-
recognized changes occur in our silver,
gold, lead. copper and antimony lodes
where the original auriferous sulphides
and arsenides and their compou nds be-
come decomposed especially when they
occur ia easily soluble rocks like lime
stone and dolomite or in readily perme-
able ones as states and schists. This ac-
counts for gold being found in different
parts Of central Nevada among the ditf.
erent metals in zones where the metallic
gold predominates. Under some con-
ditions the gold may and often does pass
into solution from its original minerals or
is re-dissolved from its first precipitation
and passes through the deposit till the
auriferous solution meets mineral ca
pable precipitating its gold which gen
orally occurs on the foot wall or on a
horse within the deposit. In this con-
nection sho Id be remembered that the
present footwall OF lode may at some
time have been the hanging and that the
direction Of the action of gravity within
an ore deposit is continually changing
from the first deposit of the sediment or
the opening of the fissure. Up to the
present day the oxidation and hydration
OF the upturned edge Of mineral bear
ing ledge be it vein or a bed prepares
an enriched zone below the surface and
brings the gold near it in metallic con-
dition and the silver in ruby and chic