Bisbee daily review., 1904-03-01
Copper Deposits
 IN THE
 Warren District
CoNTiNUATio NOE PAPER ON THE
 SUBJECT BY F. L. RANSOME. \
interesting SeoIogica! Discussion by An Eminent Authority, of Direct h. terest to Warren District Experts,

EnclrcllnS tne SliiceOuS zone are tne pale green altered limestones in which pyrite, tremolite, diopside. grcssular- ite and probably vesuvianite are the characteristic minerals. In this zone quartz is comparatively rare. Calcite. however, is abundant. and may make up half or more of the al tered limestone. At its inner edge. this zone grades somewhat indefinite ly into the siliceous zone. About its circumference it passes by obscure gradations into the unmetamor- phosed limestones of the region The rock of this zone of metamorphic silicates is softer than that of the in- ner siliceous zone. It is frequently traversed by little irregular surfaces of shearing, so that the rock tends to break along many curved surfaces inru mkny small fragments. The width of this zone cannot be stated with precision, on account of the in- definite character of its boundaries, but it may be very roughly estimated , at about 1000 feet. The zone is not, however. limited in plan to a simple concentric band about the porphyry but extends for a considerable dis tance to the northwest, alongside the Dividend fault
 The town Of Bisbee lies on the fault line. The hills northeast of thel town are composed of pre-cambrian schists. Those just south of it are upper ear boniferous limestone, with lower car boniferous, devonian and cambrian beds coming successively to the sur face along the fault to the northwest A little less than half a mile south east of the center of town the fault en. counters a mass of altered granitep DOT phyry and as simple fracture disap- pears. This porphyry, which forms Sac , ramento hill, local landmark, is very 1 irregular stock about a mile in diane ter. It has invaded the pre-cambrian per carbonifferous (propably also the ! deeper-lying elder paleozoic beds) on ! the southwest. The available evi dence indicates that the intrusion oi
 this porphyry took place after the 1islocation Of the invaded rocks by the great fault The latter probably continues to the southeast of the DOT phry mass, but it is concealed in this | direction by the younger cretaceous | beds. The paleoDcic beds forming the faulted synciine are not merely f1exed, but are cut by many faults some of them of considerable throw
 These faults are. as far as seen, oi | the normal type.
 l The ore occurs very irregularly as
 large masses within the limestone | The horizontal extent of these bodies | Is usually much greater than the yer
 tical They are rudely tabular ir
 form and lie generally parallel to the bedding panes of the limestone. As
 a rule, the important ore bodies have
 been found within distance of 100(
 feet of the main porphyry mass or oi
 the great fault Assure just northwest
 of the porphyry. In the Car work ings of the Copper Queen mine, part.
 ly under the town of Bisbee, ore bod
 les have been worked from the sur
 face down to c depth of about 400 | feet, but toward the southeast the bulk of the ore occurs at increasing depths. In the Calumet & Arizona
 mine, about $500 feet to the south oi
 the Car, no large ore bodies were
 encountered until the shaft had pen
 etrated about 800 feet below the Ieve
 at which the first ore body was
 discovered on the Copper Queer
 claim. The ore thus occurs at in
 creasing depths toward the center oi the local synclinal basin.
 With the exception of the extreme
 western part of the Copper Queer
 mine, all of the productive and i'm portant workings in the vicinity ol
 Bisbee are in the carboniferous
 limestones. It is probable the great CT part of the ore bodies occur in the granular limestones of the lower car boniferous, but the distinction be
 tween upper and lower carbonifercus
 beds can rarely be satisfactorily made
 underground. Some important ore
 bodies certainly occur in the lower
 part of the upper carboniferous. Or the ether hand, no ore bodies of con
 sequence have yet been found in the
 deeper lying devonian and cambriaI limestones. In the Copper Queer
 mine locahusage has distinguished ar
 upper lime" and Tower lime" AS
 far as could be seen. however, this
 distinction is largely imaginary and ii
 based on no constant litnoiogica1 ol structural features. The Tower
 lime" appears to be any limestone
 lying underneath the known ore bod
 ies. It is in the main lower car
 boniferous, and the ore bearing pos sibility of the underlying and nevcni