Geology of the Municipalities of Tuba and Itogon,
mapping is conducted in selected areas in the towns of Tuba and
Itogon, Benguet in compliance with the requirements for undergraduate
geology students. The study area is composed mostly of intrusive
igneous rock units. Volcanic and sedimentary rocks are also observed.
Based on field observations, the oldest rocks are meta-andesites
which are part of the Pugo Formation. These meta-andesites are
intruded by the Middle Miocene Central Cordillera Diorite Complex
(CCDC), which is composed of different diorite facies. Another set of
intrusions, composed of dacites, andesites, and volcanic breccias,
may have contributed to the uplift of the area. This event led to
erosion and eventually deposition forming the younger conglomerate
unit identified to be part of the Late Miocene Klondyke Formation and
limestone unit. Efforts to determine its absolute age and to identify
as to what formation it belongs are still on going. The youngest
rock unit observed is a breccia body based on stratigraphic position
and cross-cutting relationship.
observed in the area can be related to the regional tectonic setting.
Variations in the trends of the structures are attributed to the
tectonic history and nature of emplacement of most of these rocks.
This involves intrusion, uplift and the effect of regional stresses.
is also observed in the form of disseminations and veinlets of
sulphides. Quartz veins are relatively numerous in specific areas.
Sulphides which are common in the andesites include pyrite,
chalcopyrite and bornite. Molybdenite occurs in less significant
amounts. These are also observed in the diorites but not as extensive
as in the andesites.