Yol. 69.] GEOLOGICAL HISTORY OF THE MALAY PENINSULA. 361 



and dolerites of the Pahang Yolcanic Series have their greatest 

 development, it is unnecessary to quote scientific literature to 

 show that the difference in mineral products is consequent on the 

 difference between the nature of the igneous rocks in the Benom 

 Anticline and those in the Main Bange Anticline. East of the 

 .Benom Anticline are stanniferous granites similar to the Main- 

 Range granite. 



This difference between the rocks of the Benom Range and the 

 tin-bearing granite-ranges leads on to another interesting subject, 

 which it is impossible to discuss fully here — although it may be 

 mentioned briefly. When describing the rocks of Pulau -Ubin and 

 Pulau Nanas, 1 I remarked on the early differentiation of a granitoid 

 and a gabbroid magma under the site of the Peninsula and the 

 neighbouring Archipelago. Now, in the Benom Bange pyroxene- 

 biotite-syenite has been found ; and to the south, in the liumpin 

 district, a fine-grained norite has been collected, the relation of 

 which, however, to the Benom Granite is obscure. The presence 

 of norite suggests another intrusion from the same or from another 

 gabbroid magma, and the presence of the pyroxene-bearing rocks 

 in the Benom Bange suggests a probability of their connexion with 

 a gabbroid magma also. The difference between the felspars in 

 the Benom pyroxene-bearing rocks and those in the Pulau Nanas 

 pyroxene-bearing rocks is against their direct origin from the 

 same magma ; but it will be allowed that such rocks might be 

 derived ultimately from the same gabbroid magma, if we con- 

 sider the possibilities of a preliminary magmatic differentiation and 

 the chances of admixture of the granitic magma. The less acid 

 character of the Benom rocks, as a whole, compared with the rocks 

 of the Main Bange, may be due to such a mixture of magmas. It 

 might, however, be argued that the abundance of hornblende- 

 granite in the Benom Bange is due to the melting of masses of 

 calcareous Baub-Series rocks in the magma before it solidified. I 

 do not incline so much to this view, however, because in the Main 

 Bange it is clear that enormous masses of calcareous rocks must 

 have been stoped away — yet hornblende-granites are not, by any 

 means, so strongly developed as in the Benom Bange. It is quite 

 likely, nevertheless, that the masses of calcareous rock stoped away 

 in both ranges gave rise to some hornblende. 



It is interesting to recall Prof. F. Lcewinson-Lessing's views on 

 the origin of igneous rocks in this connexion. 2 He regards a 

 granitic and a gabbroid magma as the two principal magmas from 

 which all igneous rocks have been derived, and favours the view 

 that all syenites are only local facies of a granitic or gabbroid 

 magma. This is certainly the case with a syenite near Taiping, 

 in Perak, the rock being a local modification of granite ; but, in the 

 •case of the pyroxene-syenites of the Benom Bange, a mixture of two 

 magmas seems to be the more probable cause of their formation. 



1 Q. J. G. S. vol. lxvi (1910) pp. 432-33. 



2 'The Origin of the Igneous Rocks' Geol. Mag. dec. 5, vol. viii (1911) 

 p. 254. 



2b2 



