﻿part 3] STANNIFEROUS DEPOSITS OF KINTA DISTRICT. 



175 



on the cliff-faces ; of the very irregular outline, not only at their 

 base, but from top to base, of these cliffs ; of the sometimes 

 vertical faces (due to joint-planes) ; of the overhanging faces 

 (due to undercutting) ; of the frequent gently-sloping faces 

 showing terraces ; and of the alluvial tin-ore deposits found in 

 caves in these cliffs at various heights, sometimes hundreds of feet 

 above the valley-floor, and formed in the past by streams flowing 

 from over the stanniferous granite of the Main Range. 



IV. Alluvial Origin of the Stanniferous Clays 

 and the ' Boulder Clays.' 



The ' Grondwana Rocks ' of Kinta are mapped by Mr. Scrivenor 

 under the following headings : — Gopeng Beds, Clays with Tourma- 

 line-Corundum Rocks, Clays with Corundum Boulders, Phyllites 

 and Quartzites, Shales and Quartzite. It is stated, however, that 

 this is not to be taken as their sequence, but as a means of showing 

 the distribution of the beds in various parts of the district. 1 For 

 reasons which will appear later, the phyllites, quartzites, and shales 

 are said to represent the ' younger members of the Grondwana 

 Rocks of the Kinta District, and include mica-schists, tourmaline- 

 schists, shale, and carbonaceous shales.' 3 Now, these schists are- 

 near, or at, the granite- junctions, and are frequently veined with 

 granitic intrusions carrying cassiterite. They are being worked 

 for tin-ore, occurring in quartz- and pegmatite-veins and stock- 

 works, at Tanjong Rambutan and Ulu Gopeng on the east ; at 

 Lahat, Kacha, Papan, and Tanjong Toh Allang on the west ; and 

 at several other places on both sides of the Kinta Valley. 



The reason given by Mr. Scrivenor for regarding these rocks as 

 being younger than the ' clays and boulder-clays ' is that 



' the ground immediately above the limestone is composed of the clays and 

 boulder-clays or the remains of them, and the highest ground in the valley, 

 apart from the limestone-hills, is formed of the quartzites, etc. ; while there 

 is no evidence of the clays and boulder-clays having been derived from the 

 quartzites and phyllites when the latter formed, as they might have formed,, 

 a land-surface.' 3 



The position of these clays and boulder-clays at a lower level 

 than the quartzites and phyllites, and resting on the irregular bed- 

 rock of the valley, is, however, perfectly consistent with the alluvial 

 origin of the greater part of them, the rest being the result of the 

 decomposition in situ of the schists and phyllites, which, in places, 

 sank on the underlying dissolving limestone. Evidence will now 

 be adduced to show that all these tin-ore deposits are derived 

 from rocks proved to be in situ in the district. 



1 J. B. Scrivenor, ' The Geology & Mining Industry of the Kinta District' 

 1913, p. 28. 



2 Ibid, p. 44. * Ibid. p. 45. 



