rated by some of the deposits
at Bingham, Utah, and at Bisbee, Arizona. The primary deposition was of
chalcopyrite and other copper sulphides, together with garnet, diopside,
and other minerals known to have required high temperature in their
formation. The ore fills fissures and replaces extensive masses of the
limestone. It is likely to show a fairly sharp contact on the side
toward the intrusive, and to grade off into the country rock on the
other side with numerous embayments and irregularities. These deposits
have been enriched by weathering in the same manner as indicated above
for the porphyry coppers, but to highly varying degrees. In the Bisbee
deposits large values were found in the weathered zone, and secondary
sulphide enrichment below this zone is also important. In the Bingham
camp, on the other hand, the weathered zone is insignificant and most of
the ore beneath is primary. The weathering of the silicated limestone
gangue results in great masses of clay which are characteristic features
of the oxide zones of these deposits.

=Copper deposits in schists.= Other copper deposits, as at Jerome,
Arizona, in the Foothill and Shasta County districts of California, at
Ducktown, Tennessee, etc., are irregular lenticular bodies in schists
and other rocks, but all show relationship to igneous rocks. The Rio
Tinto ores of Spain and Portugal, which belong in this group, have been
referred to on page 108.

In the Jerome or Verde district of central Arizona, folded pre-Cambrian
greenstones and sediments were invaded by masses of quartz-porphyry, and
after further deformation, rendering many of the rocks schistose, were
intruded by an augite-diorite. Contact metamorphism along both the
quartz-porphyry and the diorite contacts was practically lacking. The
ore bodies were formed as irregular pipe-like replacements of the
schists, being localized in one case by a steeply pitching inverted
trough of impervious diorite, and in other cases by shear zones which
favored vigorous circulation. A later series of small diorite or
andesite dikes cut the ore bodies. The primary ores consist of pyrite,
chalcopyrite, and other sulphides, with large amounts of jaspery quartz
and some calcite and dolomite. They were clearly formed by replacement
of the schists particle by particle, as shown by the frequent
preservation of the schist structure in a banding of the sulphide
minerals, the residual shreds of unreplaced schist material in the