﻿part 3] 



STANNIFEROUS DEPOSITS OF KINTA DISTRICT. 



171 



to do, that they are the result of simple denudation of a strongly- 

 jointed limestone, then the position of most of the tin-ore deposits 

 at the foot of these cliffs, and resting on the weathered surface of 

 the limestone, makes it impossible for them to be as old as the 

 neighbouring granite ranges which form the sources of the streams 

 that denuded the limestone. The greater part of the deposits 

 are obviously of alluvial origin, and any doubt on that point is 

 settled by the fact that the beds of the streams which carried them 

 to their position are still being worked, in numerous cases, for tin- 

 ore on the slopes of the hills and mountains directly overlooking 

 the positions of these deposits. The streams, after reaching the 

 valleys, are frequently deviated in order that their beds may be 

 washed for tin-ore, and quite recently a great scheme was pro- 

 pounded to work the bed of the Kinta River itself. 



Some of the tin-ore deposits near the foot of these limestone 

 hills are not, however, alluvial in the sense of having been trans- 

 ported by running water, but are the result of the weathering 

 in situ of phyllites and schists, which afterwards subsided on the 

 dissolving metamorphosed limestone that has everywhere been 

 proved to underlie them at small depths. It was the failure to 

 appreciate the effect of the extensive weathering of these rocks in 

 a moist tropical climate, where the water flows for some miles over 

 decomposed granite, and is hence rich in alkalies, that seems to 

 have misled Mr. Scrivenor. He recognized, however, that the 

 position of these deposits at the foot of the cliffs was difficult to 

 reconcile with their Permo-Carboniferous age. He states that 

 1 simple denudation alone might account for them (the limestone 

 hills) if we were to regard the beds overlying the limestone floor 

 at the base of the cliffs as being recent alluvium ' 1 ; but concludes 

 that they ' owe their origin primarily to faulting,' and that the 

 main fracture that brought about their formation coincides with 

 the junction between the granite and the older rocks. No reason 

 is given for the absence of similar hills on the west side of the 

 valley, although the junction between the granite and the limestone 

 there has also been described 3 as a fault-junction. 



These limestone hills are very irregular in plan, and, in a diagram 3 

 in his memoir on the Kinta district, Mr. Scrivenor has reduced them 

 to their simplest forms, in order to show the directions of the faults 

 which formed them. The least possible number of faults is sixteen, 

 and these show fault-planes in twelve different directions. In 

 order to form isolated hills like these by faulting, the movement 

 round each particular hill must have been simultaneous, and so as 

 to explain this it is stated that they are ' huge blocks of the crust 

 that sank on to the granite magma relatively less than the sur- 

 rounding rocks when the Main Range anticline broke up.' 4 If 

 this sinking movement occurred, then it is reasonable to conclude 

 that the amount by which the limestone floor of the valley sank 



1 ' The Geology & Mining Industry of the Kinta District ' 1913, p. 14. 



2 Ibid. p. 18. 3 Ibid, facing p. 16. 4 Ibid. p. 18. 



