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GEOLOGY OF THE NEIGHBOURHOOD OF STELLFN BOSCH. I33 



the north as the farm Nooitgedacht. so the tourmahnized zone 

 must be pretty extensive. The presence of tonrmahne is, of 

 course, no proof of the occurrence of tin, but it .e^ives an en- 

 couraging suggestion of it. 



The western margin of this granite can be studied con- 

 veniently between Lynedoch and Eerste River Stations. The 

 marginal facies is non-]wrphyritic, and contains many small 

 pockets of tourmaline. Between it and the Malmesbury rocks 

 there is again a tourmaline zone, as is shown bv the occurrence 

 of boulders of quite coarse-grained tourmaline c(uartzite. 



With the exceptions of these marginal facies and of the 

 aplite and pegmatite veins already mentioned, the granite hardly 

 varies at all in apj^earance or composition. It is throughout a 

 coarse, porphyritic biotite-granite with subordinate muscovite, 

 with microcline as the commonest felspar. 



The second area of granite is bounded on the west by a 

 line which runs out from the north end of Stellenbosch Moun- 

 tain. The exact ]>osition of this line was determined at two 

 points — -one in a drain at the side of the vineyards of Coetsen- 

 burg, and the other in the bed of Kromme River, just below the 

 Co-operative Winery buildings. The boundary continues north- 

 wards into the Schoongezicht ridge, and is seen again in a kloof 

 north of the farm Cloetesdal, where some small apophyses are 

 thrown out into the slate. The eastern margin of this granite 

 tongue is hard to place, but the imperfect exposures on the top 

 and round the base of the ridge and on the Hels Hoogte road 

 indicate an approximately straight line running S.S.E. (mag- 

 netic) into Jonker's Hoek. The granite of this mass is on the 

 west side identical with that of Bosnian's Crossing, but in Jon- 

 ker's Hoek and opposite the mouth of the Hoek it has been 

 strongly sheared, and has. in consequence, become streaky, with 

 cataclastic structures. This shearing and destruction have 

 afifected not only the granite, but also the French Hoek sedi- 

 ments to the east of it, and on account of this and also of the 

 inadequate nature of the exposures the eastern margin of the 

 granite cannot be placed with precision. 



About the northern end or apex of this mass, on the top 

 of the Schoongezicht ridge, boulders of cherty quartzite. contain- 

 ing tourmaline, are to be found, indicating again a mineralized 

 contact zone. 



Near the top of the Hels Hoogte road, after traversing the 

 French Hoek beds at right angles to their strike, one meets again 

 an unsheared porphyritic granite, the margin of which runs 

 northwards towards Schoongezicht and southwards into Jon- 

 ker's Hoek. This, the third lobe of the batholith, is continuous 

 eastward to Drakenstein, and northwards towards Paarl : south- 

 wards it forms the floor of Ban Hoek and Jonker's Hoek, anu 

 eventually disa]:)pears beneath the Table Mountain Sandstone. 

 The fresh rock has precisely the same characters as the un- 

 sheared granite of the other lobes ; the western margin has been 

 affected by shearing movements along the Jonker's Hoek fault. 



