Bulletin of the Geological Society of Malaysia, Volume 19, April 1986, pp. 281 – 289
Geological Survey of Malaysia, P.O. Box 1015, Ipoh
Abstract: Available Rb/Sr whole-rock and zircon U/Pb data indicate that the granites of Penang Island were probably emplaced in the late Triassic between 22 Ma and 206 Ma. The results of K/Ar analysis of 31 biotite samples from the granites of Penang Island are presented.
A general decrease of apparent biotite ages in a south-south-easterly trend from 209 Ma to 160 Ma is evident. In the northern third of the island, the apparent biotite K/Ar ages of 209 Ma to 201 Ma are concordant with a published Rb/Sr isochron of 206 Ma. Apparent ages of 199 Ma to 179 Ma were measured from samples from the rest of the island except at the southeastern coast where 2 significantly younger ages of 170 Ma and 160 Ma were measured. This trend of younging apparent ages suggests rejuvenation on a regional scale.