Blackfoot news. (Blackfoot, Idaho) 1891-1902, 1898-05-14
BIG COPPER DEPOSITS.
Mora County, New Mexico. Has vsluabI,
Ores.


Ores
The deposits referred to are In Mora
county, New Mexico, in small valley
about thirty miles northwest of the
station of Watrous on the Santa Fe
railroad, and about one and a half
miles southeast from the village Of
Gaudalupita. The beds which contain
the copper minerals form a part of a
stratified formation-tipped up ON edge
stretching out along the valley for
over seven miles in a northerly and
southerly direction. These beds consist
OF alternating carbonaceous shales,
sandstones, sandstone conglomerates
and arenaceous limestones. The bed
ding is remarkably regular, being dis
tributed by no faults of consequence
the outcrops running along the valley
In bold straight lines for nearly its en-
tire length. At both ends of the valley
malpais" covers these outcroppings;
but they appear again on the other
side of these eruptiye masses, contin-
ing their courses undisturbed.
The copper minerals are, as far as
could be observed, confined wholly TO
the shales. This is an important point
in determining the origin of the depos-
its, and, thereby, their economic value:
The sandstone palisades which form
the eastern boundary of the valley for
its entire length appear TO rest uncon-
FORMALLY on the tilted beds. These
palisades rise 1000 feet above the val
ley at its northern end, diminishing in
height towards the south. An interest
ing feature in connection with the geo.
ogy of this valley is the masses of NAL
pals which are found at both ends of
it. This malpais forms table noun
tains, and also flowed over the surface
of the sandstone mesa back of the pal
isades
As already stated, it covers the beds
containing the copper minerals at both
ends of the valley. As far as could be
observed the malpais eruptions have
had little to do with the fitting of
these beds, or with the deposition of
the copper contained in them. Copper
minerals are found in the beds of shale
at various points along the western
side of the valley. At or near the sur
face these beds show only traces of
copper, but with a few feet of depth
the greenland blue-carbonates APP
pear, and with increasing depth these
are replaced by copper sulphides. The
carbonates are evidently the result of
the decomposition of the sulphideS, and
often take the forms of the latter,
which will be more particularly de-
scribed further down. There are sew
eral of these beds within short dis
tances of each other, separated mostly
by sandstones.
The author gives at some length his
reasons for believing that these ore
bodies cannot be accounted for as the
product of mineral springs, and also
for believing that the igenous theory
must be rejected. He thinks, on exam
lining all the surroundings of the dis
trict, very simple theory can be form
ulated.
1t is probable that back in carbonif-
erous ages there existed on this spot
an extended shore line. The waters
Were suitable for the growth of fern
trees, the remains of which can now
be found all through the shales. Into
this lagoon, or possibly estuary. a
stream emptied. 1t was stream of
considerable size because it created a
current in the lagoon and brought
down logs. which. passing over the
muddy sediment, left grooves in its
surface. The current was sufficiently
strong to give general direction to
the drift carried into the lagoon. In
some manner possibly through the
medium of some stream flowing over
mass of cuprous pyrite and empty
ing into the bayou-a solution of sui
phate of copper was introduced into
its waters, and this solution was grad
III it.- hx-4 la ,,,s..
ter deposited with the sediment. Thus
the sulphate was converted into copper
sulphide, and this later assumed the
shapes and appearances of the organic
remains which it replaced. To-day we
find the sulphide of copper imbedded
in the shales, exhibiting the forms of
the old carboniferous flora and fauna.
There are even log jams. the former
logs now being converted, to a great
extent. into copper sulphide. AS to the
reoccurrence of the shale beds, the
fact that they do reoccur may be
accounted for in several ways: There
may have been an elevation and sub
sidence of the land at reoccurring pc
RODS; or the phenomenon may be as
cribed to other causes.
1t is to be expected that surface wa
tiers, acting through the long ages since
these beds We're formed, would have
penetrated these measures to a great
er or less extent, and in doing so they
would necessarily have leached out
the copper sulphide and have redepos-
tied it lower down in the form of car
Donates. or even in the form of sui
phide, the secondary sulphate being
decomposed again by the organic mat
ter remaining in the shale In the lat
ter case fantastic shapes might origin
ate, taking the form of the channels
through which the waters percolated.
For this reason it is to be expected
that the shales near the surface do not
contain the amount of copper which
they originally held But where the
shales are fresh, and show no evil
dences of being subjected to percolat-
ing waters. it may be assumed that
their copper contents are very nearly
intact.
In the existing workings above wa
ter level there is very little copper ex-
posed, not sufficient to warrant the
working of the deposits. and unless ii
is reasonable to expect richer ore at
greater depths, these deposits are of
no present commercial value.-Engi-
neering and Mining Journal.