The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1922-08-17
THE STUDY OF FAULTING
IMPORTANT IN MINING
ROCK MOVEMENT PROBLEMS
WHICH REQUIRE PRACTl-
CAL SOLUTION.
Mining and Engineering
Journal Press

terest to miners than the ore bodies
themselves. To distinguish fault
and to be able to detect the direction
and distance of the movement which
has taken place along it, is an ac-
complshment which is a matter of
absolute necessity to the miner
To begin with. it is necessary to
lose the conception that fault is
something technical and geological
and therefore not to be understood,
except after a college course. AS a
matter of fact, college biologists have
not distinguished themselves by be-
ling especially intelligent about fault
/ ing. At the best they have small ad-
vantage over others. A fault is a
very simple thing. II is a piane-like
crack which runs through the rocks
and which has acted as a gliding
plane for the rocks on one side to
move past the rocks on the other
side. Any rigid body will crack il
subjected to strain; and If subjected
to variable and unequal pressure any
such rigid and cracked body will ad-
just itself by movement one part
moving past another all through the
rock; and this is exactly what has
happened in faulted rocks. One wall
may have moved past another in any
direction-up down. horizontally in
either direction or obliquely in either
direction. In fact, imagine such
block of cracked rock under pressure,
and one will perceive that the varia-
tions of movement are infinite. One
wall may even be rotated with refer
ence to another so that at a certain
pivotal point there will be no move
ment, and on one side of this point
the hanging wall of the fault, let us
say, will have moved upward with
reference to the foot wall, with an in
creasing fault movement as the dis
lance from the pivotal point in
creases; and on the other side of the
pivotal point. the hanging wall will
have moved downward with reference
to the foot wall. This is a movement
like that of a pair of scissors, and
such a fault may be called a scissors
fault Certain classifications of fault
movements are very old. When the
hanging wall has moved down over
the foot wall. its faulting is normal;
when it has moved up, the faulting Is
reversed. This classification is not to
be borne too strongly in mind, for
when the main fault movement is
horizontal, the relative movement as
seen on a vertical plane may have
very little significance. and may in
deed be very misleading Each fault
must be regarded as a problem in diff
ferential movement. all by itself; and
it's solution should be attempted with
out bothering to place it into any en-
pirical classification, or steering by
any book rules. First, find the direc-
ton of movement. which is not al
ways easy Situations or gougings
made by the travelling of one block
past another are valuable indexes OF
directions: but even this is not so
simple for in some cases the hang
ing wall. let MS say has first moved
past the foot wall in a certain direc-
ton and at a later recurrence Of
stress it has slipped in quite a dis
tinct and different direction. What
has been the net result of these move
ments? For what the miner wants to
know is where to find the continue
ton of his vein, that has been cut off
by the fault. After establishing the
direction of faulting, it is necessary
to find the distance; and then the
problem is solved Astoundingly ac-
curate results have been obtained at
times in the solving of difficult fault
problems. The student must use
every available local clue to this
and it is a science so var
liable that, like the act of being a de-
Lective. il can not be taught in hooks.
much less in a correspondence school.
Faulting is typically a slow pro-
cess; often a recurrent process, in
duced by repeated movements along
the same plane at different times.
a vein has been faulted,
and in the fault fissure a new vein
has been formed Then we say that
one vein faults the other.
At the Esperanza mine in FL Orc,
Mexico, the veins were traversed by
a fault and a movement of 300 feet
took place along the fault. Then the
surface was levelled off to a plane by
erosion, and thereafter a lava flow
covered the levelled outcrop of vein
and fault. Then the fault movement
was resumed and amounted to $50
feet so that the lava flow was faulted
$50 feet from the vein and all the
pre-lava rocks $50 feet. A rich ore
body was cut off at the fault; and ex-
ploration on the other side undertake
en- on the belief that the fault move
ment was $50 feet failed to find the
ore The detection of the actual $50
foot movement which was made from
very meagre data, lead to a twO-year
program Of development at the close
of which the lost ore was found and
yielded many millions of dollars. This