The Goldfield news. [volume] (Goldfield, Nev.) 1904-1911, 1905-05-12
THE GOLDFIELD MINING DISTRICT

BY o III B. HASTINGS.

st. Louis there is "A later andesite, o
quartz bearing, very sparsely so, and
no vein action is seen in it's area. East
of this again, and next to indicator
Mountain, are rhyolite hills with i'm
cluded masses of black sillcitied shale.
indicator Mouutain is entirely alas
kite, silicified, with perhaps so re rhyo-
lite dykes. These dykes are fine grained
phases Of aiaskite. They do not seem,
however, to I've merely gradations, but
are separated from the coarse alaskite
by ines rf assuring. 1t is not neces-
sary to consider Vindicator Mountain an
uplift to account for its prominence, its
hard siliceous nature is sufficient to
have protected it from erosion, in COM
parison with the surrounding country.
In fact it seems as if the topography of
| the Goldfield area is more due to erosion
than uplift, as We come to such eleva-
tons, high and low, it is found to be of
harder material than the surrounding
country, and the hills in the distance
appear to be soft tufts, capped and pro-
tected by hard eruptives or silicified
areas.
Banner Mountain and the hills be-
tween it and indicator are both defined
by their ridges OF hard silicitied ande-
site tufts, and probably owe their ex-
istence to that fact. About half way be-
tween Banner and Knickerbocker Noun
tains is a large area OF purple andesite,
apparently the crater of an old volcano,
level, while the sides of the crater COM
posed of soft tufts, have been hardened
by silicification and preserved. These
are represented by the hills already de.
scribed and the northern ridge OF
Knickerbocker Mountain, together with
the westerly spur from same.
knickerbocker Mountain, from the
north end where the ridge rises from
plain, up to the flag on the summit, is
all about the same kind of rock. silici-
fled andesite or fi.e andesitic tufts, and
it appears as if this fine ridge was due
entirely to this s~ilicitication. Myers
Mountain not SO far away, already de-
scribed, to reiterate, is seen to be com
posed of tufts, except for it's ~unexposed
basaltic neck, and to have preserved its
tufts to an almost equal altitude, by its
basaltic head-dress.
Epurth-Tbo thoor, fhat tho h1nff
bounding the malapais plateau south
and west of Goldfield is a fault scrap,
seems untenable. The area is composed,
as exposed in the water gulch, of lake
beds and tufts at its base, above them
the purple rhyolite flows, which is a fine
example OF i~gneO-auueons fusion, say
fifty feet thick, and resting Immediately
and conformably on it, a basic andesite
flow, also fifty feet thick, a dense heavy
rock. Followingthis escarpment around
to the saddle crossed by the B%allfrog-
not formed by faulting, the two lava
flows, the rhyolite and the andesite,
thin out approaching the divide, but on
the east side Of it are immediately seen
again Gaping the tops Of the hills, at
the same level as the malapais plateau,
if anything slightly higher, showing that
before erosion they extended across un-
broken. At the time of the rhyolite and
andesite flows. the underlying tuff
and wash OF the malapais mesa was
probably a lake bottom, and these two
flows have protected the beds from ero-
sion, while the softer bordering hills
have beeu carried away. While there
are many great block uplifts partially
resembling the mesa in the Great Basin
area, this does not seem to be me-.
There are signs of local disturbance at
mouth of water gulch, the beds of the
on which the tanks stand is dropped
somewhat. If the bluff were a fault
scarp, the area under town would prob
bly, be a duplication of the mesa, and its
same geological conditions found in deep
wells. The shallow wells now sunk are
either in wash or basalt.
Fifth-As to the Black Butte being a
s~tellate uplift, it was found impossible
to view it in this light, and like several
other prominences already mentioned,
regarded as owing its prominence to sill
dedication of the country. The silicified
masses browning the summit and cover
ing the sides, are the extreme products
OF alteration OF the andesite, probably
along lines OF disturbance, affording
passage for the heated waters. Though
these lines may have been fault planes,
with a relative up and down movement;
the contiguration today is due to erosion
of the softer andesite around the altered
core. While the north and south ex-
tensions may pass through the Butte, it
is hardly to be proven that the Nam
moth, &C., do so. There is a mile Of
wash covered flat between them.