Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1874-05-13
THE FORMATION or fISSuRES.
The Origin Of Their Mineral Con.
tPm1S.

The Origin Of Their Mimeral Con.
temtS.
ny A. J. brown, TREASURE CITY, NEW.
1 IA paper read at the New York meeting Of
tho American Institute Of Mining Ensi.
ncers, February "a, 1874.
II The causes that have formed fissures
L in the earth's crust, and the agencies
that have converted them into metallic
beds, are among the most important
and interesting subjects that can en-
gage the attention of the mining cnri-
nccr or the scientist. They are the
ycrv base of the whole system of vein
81 geology, and until something like a
correct theory can bs arrived at wi h
regard to them, the science as Sllcl, is
necessarily very incomplete. TIE da-
{ IA for such theory, owing to "a lack of
: careful and systematic Ob>crvat ions in
S countries prominently nlaN,lliferous.
= like Mexico and the States Of Central
and South America, are almost en-
9 ,irely wanting. Doub less there has
4 been abundant speculation on the sub
i icct, from the earliest times down to
the present. in every country where
q mining has been one of the leading in
u du.trics of the inhabitants. Perhaps
the theory of File de Beaumont more
nearly approaches satisfactory expla-
nation than that Of any contcln por,ry
authority. The most recent inve>tiga-
tons. both in Europe and on this con-
tnent, tend to produce the conviction
81 that the phenomena of metallic tisslre
8 lo,le> are III some way connected with.
and dependen. upon. plutOnic agencies
hot, however, as the direct product
of volcanic activity, but rather as the
] result of chemical agencies called into
play through its aid.
Active volcanoes generally produce
onl v the well known types of volcanic
rocks. though, perhaps, well market
cases can he shown where these con-
tain ores OF copper, ETC., evidently de
! rived from the same deep seated
source as their hyp gene ganyuc. To
prove that there is a connection be-
tween metallic lodes and plutonic
rocks, it is not necessary that the ores
should in all cases occupy assures
within the limits of MASSES of propyl-
lie, rhyolite, or other like rocks, or be
in all cases alongside of dikes of trap
rok>, though the latter is no unusual
'currcnce. The COnStock lode of
N"vada evidently occupies, through Il
part of its course at least, the same
fi>>ure which formerly gave vent to
the vast mass of propylitc that covers
the country ,elow it, and afterwards to
a limi,el outflow of ande>ite. Lode>
are often found occupying fissureS in
or beside dikes of trap rocks. The
Murphy Mine, in Ophir canyon, Nve
county, Nevada, has near its western
or foot wall, dixie Of syenite which
contains abundant crystals of bi>ulph
lie of iron. In Bunker Hill, in the
same range Ot mountains, 4 large
f>>ure lode alternateS from one side
20 the other Ola dyke ofSyenite, soi..e-
times orcupying ti>sure within the
dixie for some distance.
There is no valid reason for suppoS-
iny that the forces requisite for the
tive in the present than in vast gcolo%-
zeal ages. On TIE contrary. it is quite
certain that valuable lode> of both sill
vcr and gold have been formed as late
~ the commencement of the Post
Tertiary. Nearly every violent earih IL
quake shock is attended with Il fis>ur-
ing Of the earth's crust; and it may be
possible, and is even probable. that the
process of converting such flS-
>trc> rs remain open into metallic
lodcS, is going on at comparatively
slight depths from the surface. 1t l.
scarcely two wears March. lS12) since
the Owens valley earthquake gave us
:, sample of how fi>Sure> are actually
formed, as we'll us how strata are fault
ed and slickensideS produced. At Big
Pine the ti>SureS We're numerous ana
several miles in length, and attended
with Il marked faulting of the strata,
in places twenty or thirty feet ver'i-
callv. 1t matters not that most, If not
all. these assures closed with the sub
>ilcnce of the shocks that produced
them. The fact still remai"s, and Is
highly significant of the results of so
Unparalleled force. The great erup-
ton OF Mona loa, III the sandwich
Islands, in 1852, was accompanied with
violent and continued earthquake
shocks and a assuring of the earth's
crust in many parts of the Island.
These tiSsureS varied in leng'l from il
few yards to five miles, and i'll thick
hess from Il mere seam to three ieet III
tEeir widest parts. Some Oh theih
closed with the subSidencc of the
shocks; some were filled with injec-
tions of melted lava; and a few re-
manned open and emitted various
gases, among which could be dl>iin-
guishcd that OF sulphur, which, con.
denSing on the walls, finally closed
them, so that when the writer revisited
the Islands, in June. 1851, nine years
after the eruption, veins of sulphur
hiled such assures rs had remained
open. The last eruption is only known
10 have formed one immense tissure,
two and half miles i'll length and
half Il mile wide. through which flowed
an enormous stream of lava several
miles in length. \ correspondent of
The Scientific Press, in the last number
Tor 1873, mentions a fisSurc that was
iormed in New Zealand during an
earthquake shock in lS4S. 1t was OF
great depth, fifty miles in length, and
eighteen inches wide. In Central and
south America, the assuring and fault
ing OF the strata is a usual occurrence
during the violent earthquake shocks
so common in those countries. Such
are few OF the constantly recurrin;,
evidences that assures are actually
'orncd by volcanic force.
3 The question next naturally arises,
now are they filled? and whence do
.''eS derive their material? Evidently,
'Hc same agencies that formed the ti>'