The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1909-10-02
GEOLOGICAL PROBLEMS RAPIDLY BEING SOLVED

ore deposition. The district abounds in illustrations of the fact that
assuring, apparently of the most favorable kind, is not necessarily fol
lowed by the accumulation of an orr body. The assure complex must
evidently be connected with still deeper channels in such a way as to
give access to ore-bearing solutions, and probably also with lateral
and superficial channels through which other solutions could pass to
mingle with the waters Of deep origin and precipitate their valuable
constituents. Thus locality and the features of a former topography
we're probably both of great Importance in determining whether a
given mass of shattered rock should become an ore body.
..That some further notifications of the original shapes of pay
shoots take place in the course of oxidation is highly probable,
although the steps of such change can not usually be traced. Oxida-
ton implies changes in volume of the constituents of the mass with
more OF less gravitative readjustment n settling, minor assuring, and
sol migration of material by resolution and redepostion.
$50 far a known the re bodies have not as a rule been greatly
modified by faulting subsequent to ore deposition. In this respect
they differ in striking fashion from the veins of Tonopah. 1t must
be pointed out, however, that the difficulties in the way of the recogni-
ton of notable fauhing at Goldfeld are very great The ability to
recognize important dislocatons depends very largely upon the de-
gree to which the faulted structures were initially regular and per-
sistent. When, for example, a welldefned regular vein which has
been followed for some hundreds of feet ends abruptly at a assure
filled with attrition products, faultlng is at once suggested and IN
many Eases is easily demonstrated.
Erratic Changes Without FaulMng.
sAt Goldfeld, however, the initial regularity is lacking. tt
known that r bodies in this district show unexpected and erratc
changes in direction and may terminate abruptly without fauhing.
There is in many cases no a priori ground for supposng that beyond
the apparent end Of an. ore shoot is another body, once contiguous
with it, but now displaced. The evidence of movement both in and
around the Goldfeld ore bodies is abundant, but the Interpretation of
this movement-the discrimination between slips Of structural i'm
portance and those whose total displacement is measurable in inches
rather than feet-is a $ a rule impossible n inconclusive. If a pay
shoot ends at a seam of gouge, and if a few hundred feet away an
other pay shoot is found on the other side of a gougefned assure.
there is as a rule no means of identifying the two bodies S originally
part OF the same mass, nor can it be assumed in this district. where
gouge seams are known to bend through angles of 80 degrees or more,
that the gouge in contact with the two masses of ore occupies one con-
tinuous assure.
The recognition OF alunite a S a characteristic constituent of
The Goldheld ores and the demonstration of it's genetic relation to
them establishes a new type-that of alumtic and kaolniic gold
quartz vans-in the classification of epigenetc deposits based upon
n KIND OF metasomatism effected in the wall rock by the ore-bearng
solutions While the Goldfeld deposits ar probably too irregular in
form to come under the usual definition of vein, yet in all that relates
TO genesis OF the ore there is ne essential difference between them
and what is usually termed a metasomatc assure vein.'