Santa Fe new Mexican. [volume] (Santa Fe, N.M.) 1898-1951, 1903-02-25
An Interesting and Author
itative Description Pub
lished by the Engineering
and Mining Journal.
REGION RICH IN MINERALS
The Origin Of the Gold, Galena,
and Copper Deposits in South
ern Santa 5e County and a
Description of the Formation
in Which They. Are Found.

The Engineering and Mining Jonurnal
of last Saturday published an interest
ing six column article on the ore de-
posits of the San Pedro district in SAM
ia Fe county The article Is illustrated
with photographs and drawings and Is
written by Richard s. McCaffery, man.
ager of the copper mines of the Santa
Fe Gold and Copper Company at San
Pedro, in conjunction with Morrison B.
Young. The following is a synopsis Of
the article: q
In the southern part of Santa Fe
county there are three groups of noun
tains each of which penetrates the Car
boniferous and Cretaceous sedimentary
strata as unit and presents in the
main the same characteristics and ap-
pearance. They extend in north and
south line and in order from the north,
are the Ortiz, the Tuertos and the
South Mountains. The region has long
been known for it's mineral wealth.
The mountains present a striking
feature, which first attract attention
as one approaches the district over the
plains from the east. They resemble
each other so closely in appearance and
height that the question naturally aris-
es: Are not the three related In
some way geologically? To the north
is the Ortiz group, cluster Of sharp,
cone-like peaks formed by the breaking
of the eruptive syenite-porphyry
through the fiat beds of limestone and
sandstone of the Carboniferous and
Cretaceous age. These beds have been
slightly lifted by the intrusion, and
slope away from the mountains with a
gentle and even dip. Four miles to the
south is the Tuerto or San Pedro group,
the geology of the western portion OF
which is the one exception to the rule
of this trio. This western part consists
of San Pedro mountain proper, the
greater part Of which Is formed OF tilted
sedimentary beds; but the eastern part
of the group, including Oroquai noun
tain, consists entirely of the eruptive
sysnite- -porphyry, with its sharpt topo-
graphy similar to the Ortiz group.
Again, three miles farther south, ia
South Mountain, which really includes
several peaks and numerous spurs. This
is also formed by an intrusion OF sye-
mite -porphyry, and shows the same to-
biography as the first two groups.
A short distance north of the Ortiz
mountains, but beyond the area of erup-
tives, is situated the colliery town OF
Madrid, where the Colorado Fuel and
Iron Company is working beds Of both
bituminous and anthracite coal. In the
foothills northeast of the Ortiz noun
tains is the ancient mining village Of
Dolores. On the west side of the Tuerto
group is Golden, a small adobe town In.
habited mostly by natives, who work In
the neighboring mines or who drywash
the placers in the vicinity. About two
miles south of Golden is San Pedro
built up chiefly by the development OF
the copper properties thereabout. Al
though the region has been known for
very long time, there are only a few
mines which have reached any note
| worthy development in their under.
ground workings, so that in many cases
the Interpretation Of the geological fea'
lures of the ore deposits is difficult.
The ore deposits may be divided into
four classes: ~ Contact-deposits OF
copper; (2) lead-silver chinneys: (3)
gold-veins; and (4) gold placers.
Under the first head come the depos-
its worked for copper in the immediate
neighborhood OF San Pedro. AS men
toned before, the western portion Of
the Tuertos is formed of syenite-por.
phyry with a crown Of limestone ant
shales, which are intensely metamor
phosed, and which contain the copper
ores The deposits are OF tht
class recently described by Lindgren a.
contact deposits. The origin OF the orr
is certainly due to the pneumatolyti'
action resulting from very forcibi'
intrusion OF molten magma from tn
earth's interior among beds Of limestone
Gases and vapor were liberated ant
caused to penetrate into the cracks ant
crevices of the superintendent mass
The limestone has been replaced b.
massive garnet, which is In some case
$50 feet thick. In intimate association
with the garnet the ore occurs .
chalcopyrlte; while its associated mi
nerals are specular hematite, epidote
vesuvianite, wollastonite, quartz an
; calcite. The ore is always accompanie
by garnet, although the garnet does no
in all places carry ore. When tn
garnet carries the ore, the chalcopyrtt
is disseminated throughout its mssi
and appears to be Of synchronous origin
(To be Continued.)
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