| Abstract |
To meet the rapidly increasing demand of electricity and in line with the National The absolute ages of selected volcanic rocks were determined in order ta refine the working stratigraphy ... _._ ze Philippine geothermal areas - Mt.Canlaon,. Lab0 and Cabalian. The rock dating methodrr used are fission-track fl) and thermoluminescence (TL) which are suitable for measuring the ages not only of young, flesh volcanic rocks btrt also of hydrothermal events in altered rocks Zircon morphology was utilized to correlate various lithologic units that might be derived from the same magmatic source and to deduce the probable temperature of the magmatic reservoir. Fission-track dating yielded ages of 0.27 Ma for dacites in well LB-2I) in Mt. Cab0 and 1.81 Ma for dacites in well PT-ID in Mt,Canlaon which are both consistent with the Pleishcene uges of the Lab0 and Canlaon Volcanics, respectively. It also gave a 1.62 Ma age for silicic andesites in MC-2 indicating that these volcanic rocks should be correlated with Pleistocene Canlaon Volcanics, and not with Pliocene Caliiing Formation. The latest hydrothermal regime in Mt. Lab0 was estimated to be 0.32 MaJi.om F2' age of altered dacites in LB-1D. Results of fission-track dating and zircon morphology anabsis revised the working stratigraphy of Mt. Canlaon but validated that of Mt. Labo. Using zircon data, the source magma temperature of Pleistocene volcanics was estimated to be -845OC in Mt. Labo, and -68OOC in Mt. Canlaon. In Mt. Cabalian, thermoluminescence data suggest a Pleistocene age (49il--670 ka) for Tamar F701canics, initially postulated to be Late Pliocene. TL also confirmed the Pleistocene ages of Cantodoc (510 kn) and Cabalian (I 7 ka) Volcanics, and implied the age of the latest hydrothermal event (5-6 ka) in the area. |