K-Ar mica dates for granites from the Bujang Melaka area

Author : Kwan, T.S.
Publication : Bulletin of the Geological Society of Malaysia
Page : 79-86
Volume Number : 24
Year : 1989
DOI : https://doi.org/10.7186/bgsm24198907

Bulletin of the Geological Society of Malaysia, Volume 24, Oct.1989,  pp. 79 – 86

K-Ar mica dates for granites from the Bujang Melaka area


Geological Survey of Malaysia, Alor Setar


Abstract: K-Ar analysis of micas from 12 localities in the Bujang Melaka pluton yielded dates ranging from 131 ±5 Ma to 235 ±8 Ma. The anomalously old dates are ascribed to samples that have been probably contaminated with sources of radiogenic argon. On the other hand, thermal influence in the vicinity of fractures is deemed responsible for the partial resetting of the K-Ar systems in samples which are too young. In general, the rest of the K-Ar dates are in agreement with those of Bignell and Snelling (1977), and are concordant with their established Rb-Sr whole-rock isochron age of 218 ±5 Ma for the Bujang Melaka pluton. No significant time lapse is evident from the K-Ar data for the different varieties of granites in the area, thus suggesting that these probably represent different consanguineous phases of the same pluton. A single K-Ar date of 211 ±6 Ma for muscovite from greisen in the Chenderiang area (Bignell and Snelling, 1977) supports the hypothesis that the pegmatites and associated mineralisation of tin are related to the residual aspect of this same intrusive event.