Bulletin of the Geological Society of Malaysia, Volume 45, May 2002, pp. 231 - 234
Department of Geology, University of Malaya, 50603 Kuala Lumpur
Abstract: Occurrence and implications of magmatic epidote in granitic rocks is reviewed. The presence of magmatic epidote in granodiorites, tonalites and trondhjemites is commonly used as evidence of magma crystallisation at pressure in the region of 6 to 8 kbar. The epidote is easily identified as they are usually euhedral, overgrowth on euhedral allanite, associated with magmatic flow, included in primary muscovite and have fine scale oscillatory zoning. The concept of magmatic epidote and its pressure is apply to granitic rocks from Peninsular Malaysia. Work on the barometry of Malaysian granitoid based on the aluminium content of amphiboles indicate that the highest crystallisation pressure of the granites is 4.98 kbar, which is below the crystallisation pressure of magmatic epidote. This may suggest that the Peninsular Malaysia granitic magmas may not have crystallised the epidote at low pressure.