GEOLOGICAL AND
GEOCHEMICAL INVESTIGATIONS
OF THE COPPER-ZINC DEPOSIT AT DUPAX, NUEVA VIZCAYA
RUDY C. OBlAL
ABSTRACT
The copper-zinc deposit is disposed in
an area underlain chiefly by sedimentary
rocks with intercalated volcanic rocks
which are invaded by dikes and sills of
basic to intermediate composition. The
deposit occurs as massive sulphide
replacement bodies in agglomerate and
sulphide disseminations in silicified
elastic sedimentary rocks. Major
structures strike northwest and appear
to conform with the trend of the zones
of mineralization. The principal ore
minerals are sphalerite, chalcopyrite,
tennantite (?) and secondary covellite.
The best grade ore exposed in the area,
as reported by Lepanto Consolidated
Mining Co., contains an average of
27.87% zinc and 2.62% copper with
subordinate amounts of gold and silver.
Stream sediment and soil samples were
collected and analyzed for copper and
zinc by rapid colorimetric procedures.
Anomalous stream sediments near
sub-outcrop ping ore attain a maximum of
750 ppm copper and 780 zinc, Normal
combined copper and zinc content ranges
from 25 to 115 ppm. Copper and zinc in
the weathering profiles increase with
depth both in the unmineralized and
mineralized outcrops. The rectilinear
soil sampling revealed anomalies
disposed along a general north-south
direction with metal highs mostly
related to mineralized exposures. Peak
values reach 500-800 ppm copper and 350
ppm zinc, compared with normal contents
ranging from 25 to 100 ppm copper and
from 0 to 50 ppm zinc. These geochemical
results tend to show that a commercially
important orebody may occur beneath the
500-800 ppm copper ground or slightly
upslope.
Geological
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