K-rich Basalt in the Bukit Mersing area, Third Division, Sarawak

Author : Nur Iskandar Taib
Publication : Bulletin of the Geological Society of Malaysia
Page : 67-73
Volume Number : 52
Year : 2006
DOI : https://doi.org/10.7186/bgsm52200610

Bulletin of the Geological Society of Malaysia, Volume 52, June 2006, pp. 67 – 73


K-rich Basalt in the Bukit Mersing area, Third Division, Sarawak

Nur Iskandar Taib

Dept of Geology, University of Malaya, 50603 Kuala Lumpur


Abstract: The basalts exposed near Bukit Mersing, Sarawak are early Eocene in age, and lie conformably over the highly folded, imbricated metasediments of the Rajang Group. Initially thought to be ophiolite, it lies close to the “Tatau-Bukit Mersing Line”, which was thought to be a major thrust fault or terrane suture, containing obducted ocean floor material. The one analysis published in 1957 showed a K2O value of 2.82%, too high for ocean floor basalt produced at a spreading center. New analyses confirm that K contents in these rocks are high. The K is hosted in K-feldspar rims around plagioclase phenocrysts. Based on the chemistry, and on field relationships, the Tau Range basalt is not ophiolite, but is likely to be Oceanic Island basalt, developed over oceanic crust, caused by short-lived hot spot magmatism.


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