The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1908-12-12
Fumarolic Action

The intense faulting at Goldfield per-
mitted the ascent of hot fumarolic va
pors from underlying igneous magmas.
These vapors, penetrating the minute
fractures and reacting upon the field
spar in the dark-colored andesites, al
tered them so intensely as to make them
appear as entirely different formations,
and introduced the valuable metals as
irregular determinations. The subse-
quent topographic development of the
lower ground at Goldfeld is due to the
intense SCATTERING of the cross-faults
and the ascending of the fumarolic
vapors, which SO softened the rocks
relative to the harder unaltered rocks
as to permit more rapid erosion.
The gold and accompanying minerals
were disseminated in the countrp rock,
and the country rock altered by these
hot, supposedly acid volcanic vapors,
rising from some deeper magma below.
These vapors altered the feldspar into
kaolinite and %alunite and segregated
the quartz into the fine h~ornstone-like
masses. And still more important, they
at the same time carried, introduced and
disseminated gold into this altered
matrix, thereby Undertaking the altered
ground.
The following quotations from Ran
oo-,o 1a,I Nth +ba oro laao.o. .1J.,
tions:
"The neurological character of the
Goldfeld ores and the alteration of the
wall rock show that the solutions or
vapors which deposited them carried
gold, bismuth, anthony, a little arsenic
and tellurium, hydrogen sulphide and
probably sulphurous and sulphuric
acids.
"Two general hypothesis are enter
these solutions. They came from above,
either the sulphurous or sulphuric acid
having been derived from the everything
deposits of oxidizing sulphides; or they
came from below. In the former case
the solutions were, presumably, cold;
in the latter case they were in all prob
ability hot. The intensity of the alter
alton and the character of the solution,
as shown by the composition of the ores
and by the metamorphism of the eoun-
try rock, point to hot ascending waters
as the effective agent. The difficulties
in the way of the descensional hypo-
thesis appear to be unsurmountable.
Gin spite of the mass Of evidence
which indicates the deposition of a
large class of gold veins by highly sill
cious alkaline solutions, it is clear that
some deposits, and those of remarkable
richness, may be formed by acidie solu-
tions. The metamorphic agent was evil
IDENTIFY a strong acid solution carrying
sulphydric and sulphurie acids, and pos
sibly s%ulphurous acid.
"The large percentage of loss in cal
cium, potassium and sodium shows that
the active solution was far below its
~saturatior point for these elements and
VAST therefore, entirely different in
character from the supposedly alkaline
solutions which deposited the large
class of serieitic and c~aleitic gold
quartz veins exempliied by those of
California.
whether the sulphurie acid which
was doubtless the direct agent in the
Of the alunite was present in
the original solution from the first, or
it was derived from the hydro
gen sulphide by oxidation at some stage
in the movement Of the solution to.
ward its point Of attack upon the rocks
now visible, is an undecided question.