Bulletin of the Geological Society of Malaysia, Volume 43, Dec. 1999, pp. 513 – 528
1Department of Geology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor D.E.
2Malaysian Institute of Nuclear Technology (MINT), Kem. Sains, Teknologi & Alam Sekitar, Bangi, 43000 Kajang, Selangor D.E.
Abstract: Seventy one samples of granitic rocks have been collected from Peninsular Malaysia, covering Langkawi, Ipoh, Kuala Lumpur, parts of Johor, Pahang, Kelantan and Terengganu to represent the granite provinces of the Peninsula. Included in the samples are the Cretaceous granites from Gunung Ledang, Batang Melaka and Gunung Pulai. The samples were crushed and anlaysed by Instrumental Neutron Activation Analysis (INAA), and values obtained were normalised against chondrite.
The results indicate that the total rare earth elements (IREE) are generally low with a range of 85- 414 ppm. The Langkawi granite especially have low IREE values, usually less than 200 ppm while those of the Main Range, Central and East Coast Provinces granites have contents higher than 200 ppm. The East Coast samples have a wide range, from 85 to 327 ppm. Out of the nine samples of the Cretaceous granites, six samples have values of less than 200 ppm while the highest value recorded for the group is 231 ppm.
The shapes of REE patterns for the granitic rocks obtained varies from typical “bird-wing” pattern, with a distinct negative Eu anomaly, to a simple upward-concave pattern with a hardly visible Eu anomaly. The negative Eu-anomalies have degrees of magnitudes, but most are small to moderate, clearly seen on their REE curve. Exceptions are from Jemaluang and Kledang granites that have moderate to large negative Eu anomalies (Eu/Sm 0.0009-0.074). The Central Province and the East Coast granites have dominantly small to moderate anomalies, together with patches of granites with small or no negative Eu-anomalies.
Based on the REE patterns, the Peninsular Malaysian granites can be divided into two groups, a) with anomalous Eu values and “bird-wing” REE pattern from the West Coast Triassic, parts of Central and East Coast Provinces, and b) without or with small Eu anomaly from the Cretaceous granites of the West Coast, granites of Gua Musang area and granite patches from the East Coast Province.
The non-anomalous Gua Musang granites seems similar to the Noring granite and may be related to the Cretaceous granites of the southern Peninsular. The non-anomalous East Coast granite is related to the I-type granite, whereas anomalous ones in the Province is from S-type, like those of the Main Range.
The anomalies are due to partial melting or fractional crystallization or both, of parental materials from a sialic basement originally rich in plagioclase feldspars. The dominant shapes of REE patterns in the Peninsular granites could be explained as such. But the small to non-anomalous patterns in the Cretaceous granites are probably due to a poor plagioclase source. The Cretaceous southern Peninsular granite is derived from a primitive mantle source. The non-anomalous I-type granite in the East Coast is derived from an oceanic or primitive mantle source.