Tonopah bonanza. [volume] (Butler City [i.e. Butler], Nev.) 1901-1909, 1904-09-17
f
The Geology of Goldfield by Mar
shall ID. Draper.

1lO GllEli10I dlN AAAiAh w. 1850
of New York in it's issue of the Sth
inst. contains an interesting Illus
trated article on Goldfeld, by Mar
shall D. Draper, a mining engineer.
The article is too long for reproduc-
ton, but Mr.. Diapers opinions of
the geology of the district are re-
printed here and in view of the opin-
ions recently expressed by Leon Do
minian and e. p. jennings will have
a special interest for our readers:
1.-THE local geology is not so com
pick as that of Tonopah, and differs
materially from it in exhibiting far
less faulting, and also in the absence
of such a Gaping Of eruptive rock as
covers the apex of the veins Of Ton
opah.
In general the topography is doml-
mated by rolling hills, with occasional
higher buttes. Within this area,
which seems to be the center of the
greatest activity, there have oc-
Cured several successive dispositions
or flows of andesite (and more To-
} cally, ~rhyolite) finally capped by ba-
salt. The latter is comparatively
thin and is spread over a much
? greater area, but It has been largely
, eroded, leaving only remnants; good
2 examples of this occurrence being af-
+ forded by the two lava capped buttes
about a mile southeast Of Goldheld
Further south, instances were noted
where this rock was more basic, APP
preaching a %peridotite; elsewhere
!, also, the rock contained large preno-
: crysts Of hornblende and Divine, Civ.
! ing a porphyritic habit. This forma-
; ton is later than the veins and it has
j evidently no connection with the ore
deposits.
% Erosion of this Gaping basalt ant
the underlying porphyries affords il
distractions Of the flow structure o
e. the porphyries and their approx
a mately horizontal deposition. o.
le the south end of Columbia mountain
ty this may be seen, where the porphy
n ries lie slightly tilted, showing til
ne qualification, or rather low-lines
dipping toward the east or southeast
At this point they rest directly on
~ comparatively coarse- granite roc
:, which outcrops on the west side {
the mountain. This granite rock
or through its scarcity of museovite o
h. biotite and somewhat pegmatiti
~ structure, is probably the 'alaskit'
If mentioned in the notes of Mr.. j.. j
or Spur. The occurrence OF this roc
go was not noted elsewhere in the di,
trict, and at this place it seemed I
n. possess more the characteristics
he an old plutonic rock, rather than
r successor, or even a contemporary,
Id of the porphyries.
an Unless the porphyries occupy
If. basin in the granite in a ann sin
* liar to the Cripple Greek %occurrenc
cir il would seem from the dip of the la.
bv ers that the granite will be encou
RS tered in depth, in the January al
.at Red Top, and perhaps in the neig
boring mines also. From the limit,
data o%btainable, the minimum dep
at which the granite may be e
MS pected in the Red Top shaft is l,50
ate #. / quote this in the light OF an
teresting possibility rather than
let probability, because, from the ia
rse that the granite outcrops only in o
quo other place some five miles to t
WY southwest and outside of the miner
ma bearing area, it might be predicat
lct, that none of the mines so far open
! IL will encounter the granite at any {
est binary depth. Shafts sunk on
'oiy western slope Of the ridge of Colu
bia mountain (where consideraI
high-grade float has been -four
llne may, however, strike the gran.
lty, within 800 or 1000 feet. Such {
yea peetation may be eliminated entire
re- from the future operations OF mir
lying further east and south, such
'ine the Jumbo, St. Ives, Florence a
others.
In general. the trend Of the We