The Philippine "Moblle Belt" region is a
principal source of metallic ores of
magmatic and hydrothermal origin.
Several tectono-magmatic regimes are
involved in its gradual transformation
from eugeosynclinal condition during
Cretaceous into a platform by the end of
The involved tectono-magmatic regimes
may be classified in a general way as
follows: (1) a non-differentiating type
of magmatic regimes with indicated and
(or) implied tensional tectonics. Such
type apparently attends depositional or
sedimentation periods; (2) a
differentiating type of magmatic regimes
which is generally synchronous with
periods of orogenic movements or what
appears to be periods of general crustal
The two types of regime occur
essentially in alternating periods.
Minor ore depositions are related to the
first type. The majority of ore deposits
are related to activities produced by
the second type, which occurred in at
least four periods.
The first period (from Late Cretaceous
to Early Paleocene) is represented by
magmatic differentiates of ultramafic
suites-gabbro to diorites. Ores of
chromite, nickel sulfides, hypothermal
high grade copper sulfide veins were
The second period, (Late Eocene to
Oligocene) produced small masses of
diorite to quartz diorite intrusives and
volcanic differentiates of andesitic to
dacitic composition. Large deposits of
disseminated copper sulfdes, associated
with small amount of gold, silver,
molybdenite, and traces of lead and zinc
ores are represented.
The third period, (Middle to Late
Miocene) formed predominantly quartz
diorite batholiths and differentiates of
diorite, diorite porphyry, granodiorite
and dacite and volcanics of andesite to
dacite and possibly to rhyolite
composition. Associated ore deposits
include pyrometasomatlc iron,
disseminated copper, vein and(or)
replacement copper, lead and zinc, gold
and tellurides, some amount of "kuroko"
type ores and cupriferous pyrite.
Associated other metals include some
molybdenum and silver, and small amount
of cadmium and mercury.
The fourth period, (Late Miocene?,
Miocene and later) which can well be a
post-platform regime have essentially
micro-diorite-andesite to dacite
intrusions and extensive volcanism of
similar composition, andesite, to dacite.
Related ore deposits include
sulfo-arsenide-antimonides of copper,
gold and gold tellurides, silver sulfide
and some associated lead and zinc as
well as cinnabar.