148 R. A. Far qui tar son — Petrology of N. Kalgoorlie, 



^ Mr. Osborne White is also of tlie opinion that tlie excavation of the Goring 

 Gap was begun in long pre-Glacial times. 



^ T. I. Pocock, The Geology of the Country around Oxford, Mem. Geol. 

 Surv. England and Wales, 1908, pp. vi, 142. 



■^ H. J. Osborne White, " On the Origin of the High-level Gravel with 

 Triassic Debris adjoining the Valley of the Upper Thames": Proc. Geol. 

 Assoc, vol. XV, pp. 157-74, pi. vii, 1899. The view that the clay with flints 

 on the Buckinghamshire hills is of glacial origin has been maintained by 

 Sherlock & Noble (Quart. Journ. Geol. Soc, vol. Ixviii, pp. 199-212, 

 pis. xii-xiv, 1912). In the discussion on this paper the authors' views were 

 generally rejected. 



^ A. E. Salter, " Pebbly and other Gravels in Southern England " : Proc. 

 Geol. Assoc, vol. xv, pp. 264-86, 1899. 



II. — jS^otes on the Petrology op a poktiox of the North 

 Kalgoorlie Field. 



By R. A. Fakquharson, M.A. (Oxon.), M. Sc, F.G.S., 

 Petrologist to the Mines Department of Western Australia. 



(PLATES VI AND VII.) 



{Concluded fro7it the March Number, j). 114.) 



TmOM the foregoing analyses there is little doubt that the rock 

 _ is a hornbleude-quartz-keratophyre. The term porphyrite, 

 however, lias been adopted in the mapping for convenience. It is 

 worthy of note that a very similar rock, though greenish in colour, 

 has been already described from Kanowna by the writer.^ In the 

 latter, silica amounted to more than 71 per cent, while soda reached 

 7"86 per cent; potash was again absent. 

 1^23,1 G.M.L. 4458 E., Hyman North.- 



The,,rock is finer in texture than the preceding one, but has no 

 remains of hornblende phenocrysts, and the ground -mass is of very 

 fine grain, and is intermixed with fine flakes of muscovite. A few 

 of the felspar phenocrysts are cracked. There are a few aggregates 

 of a yellow chlorite, some brown-red grains and dust of iron-ore. The 

 'ms^trix' of 12331b, G.M.L. 4458 E., Hyman North, is similar to 

 12237, though the former shows unmistakable evidence of shearing 

 action, not only in the parallel orientation of sericite fibres and the 

 presence of brownish-yellow flakes or spots of chlorite, but also in 

 a * lined ' or ' grated ' appearance in section, due beyond doubt to the 

 sliding of one portion of the mass over another. 



12316 (about 5|- chains north-west of south corner of G.M.L. 

 4161 E.) is very similar in section to the previous specimens, but the 

 felspar both in the phenocrysts and in the ground-mass is almost all 

 altered to sericitic aggregates, amongst which the quartz plates are 

 easily visible. 



12368, 120 ft. level G.M.L. 4406 E., Hyman, is distinctly 

 porphyritic with ferruginous outlines of former hornblende. 



1 Bulletin No. 47 G.S.W.A., Petrological Notes, p. 71. 



■^ M.C. = a weathered brownish rock. S. = minerals : felspar, quartz, 

 chlorite, sericite, and iron-ore. 



