2004 Volume 26 Issue 3 Pages 273-283
Tawau in Sabah is only one geothermal area related to the Quaternary volcano in Malaysia. Many hot springs and alteration halos are recognized in this area. The Quaternary eruptions were proved by two age data of 27000yBP by 14C and 1.62Ma by K-Ar methods. However, the age data are not enough to prove Quaternary volcanic activity. New age data of Quaternary volcanic rocks have been obtained for 12 samples by thermoluminecence (TL) method. The youngest age obtained is 0.09Ma for a monogenetic basaltic cinder cone. Ages of such young basaltic volcanos are O.IOMa and 0.11Ma (same outcrop) and 0.14Ma. Ages of dacitic volcanic rocks widely distributed at the southern foot of Maria volcano rage from 0.34Ma to 0.45Ma (4 samples). The ages of underlying andesite lava range form 0.27Ma to 0.52Ma (4 samples). We obtained preliminary age of 0.7∼1.2Ma for this andesite lava formation by weathering correction. Although the relation between such age data and stratigraphical succession is still unknown, such new age data clarified the existence of volcanic activity in the Middle Pleistocene. Alteration ages of 13 samples were also measured by TL method. The youngest ages obtained are 0.15Ma and 0.19Ma for the Upper Tawau hot spring area. Other ages are widely scatted from 0.27Ma to 0.66Ma. They were used for construction of thermal history of each area. Alteration minerals were identified for 9 locations. Temperature inferred from alteration minerals is roughly estimated around 100∼200°C. Tawau area is expected to be a target for further geothermal exploration for medium temperature (around 200°C) based on the preliminary assessment by the above TL ages and other reported data.