664 



UK. J. A. THOMSON OX THE 



[Dec. 1913, 



The contact-altered hornblende-schists are penetrated by dykes 

 of quartz-porphyry, which have the same trend as the foliation 

 of the schists, and yet clearly belong to the granite series. In no 

 case of this kind, however, has it yet been demonstrated that the 

 foliation of the hornblende-schists is parallel to the major axes of 

 the intrusives from the metamorphism of which they have arisen. 

 Although the Kalgoorlie albite-porphyries are sometimes very little 

 altered, while the quartz-dolerites, when not metasornatized, are 

 always metamorphosed into amphibolites, this difference of their 

 state of alteration need not prevent us from considering them as of 

 approximately the same age : for it is well known that the original 

 pyroxenes and lime-soda felspars of quartz-dolerites are unstable 

 under pressure-metamorphism, while under the same conditions 

 the albite of the porphyries is eminently stable. 



Two facts speak strongly for a magmatic relationship between 

 the albite-porphyries and the quartz-doierite series. The first is 

 the close chemical similarity between the former and rocks 

 associated with quartz-dolerites in other parts of the world; the 

 second is the albitization of the quartz-dolerites. These two facts- 

 are really interdependent. 



The folloAving table of analyses illustrates the close similarity of 





XVII. 



XXXV. 



XXXVII. 



XXIX. 



XXXVI. 



■ 1 

 XXXVIII. 



Si0 2 ■;..' 



TiO 



Al»6 3 



F&jO-j. 



Feb 



48-86 

 0-22 

 14-91 



11-13 

 0-90 

 7-65 



12-19 

 2-58 

 0-19 

 1-51 

 0-04 



none 



100-18 



C.C. 



Williams. 



50'55 

 1-58 



15-00 

 2-54 

 7-90 



6-25 

 7-85 

 353 



no 



3-14 

 0-55 



48-02 

 3-36 



13-03 

 2-11 

 9-99 

 tr. 

 4-21 

 9-77 

 2-17 

 0-49 

 4-27* 

 1-05 

 0-395 



0-08 

 1-24 



100-18 



J.D. 



Falconer. 



68-12 

 0-62 



15-97 

 1-09 

 2-27 

 tr. 

 0-92 

 0-71 

 6-03 

 1-29 

 0-29 

 0-17 



1-13 



98-61 



E. S. 



Simpson. 



71-18 

 0-48 



14-89 

 211 

 1-21 



0-14 

 0-82 

 6-85 

 1-70 

 0-64 

 0-24 



71-26 

 0-28 

 11-87 



o-io 



2-12 



0-06 



1-08 



2-88 



673 



0-054 



2-71 * 



0-62 



o-io 



0-009 

 0-256 



100-12 



J.D. 

 Falconer. 



MnO 



MgO ... 



CaO 



Na-O 



KoO 



H*0+ 



HMD- 



P 2 5 



CO. 



F 



FeS 2 



Totals... 



Analyst ... < 



99-99 



100-26 



J.V. 



Elsden. 



J. V. 



Elsden. 



* H 2 + and C0 2 are reckoned together. 



XVII. Qnartz-dolerite ampliibolite. Kalgoorlie. (See also p. 645.) 

 XXIX. Albite-porphyry. Kalgoorlie. (See also p. 659.) 



XXXV. Diabase (qnartz-dolerite). Carn-Llidi, St. David's Head. J. V, 

 Elsden, Q. J. G. S. vol. lxiv (1908) p. 281. 

 XXXVI. Soda-aplite. Carn-Llidi, St. David's Head. Ibid. p. 283. 

 XXXVII. Quartz-diabase. Kettlestoun Quarry. J. D. Falconer, Trans. Roy, 



Soc. Edin. vol. xlv, pt. 1 (1906) p. 147. 

 XXXVIII. Segregation-vein, Kettlestoun Quarry. Ibid. 



