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National Research Council ot the Philippines






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 Tertiary.

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 compression.

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 deposited.

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.





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