660 REPORT— 1897. 



tinct passage outward or upward from the granite mass. The series of thin sections 

 examined, as well as the hand specimens themselves, show every stage in the pro- 

 cess, which has heen carefully studied. 



In the first place, as a result of dynamic action, the orthoclase is converted 

 into microcline with the incipient development of sericite, which gradually 

 increases iu those specimens where the greatest perfection of the ' cross-hatched ' 

 microcline structure is reached. In these the individuals of quartz and felspar 

 have undergone rather extensive fracturing, hut with little or no movement apart 

 of the fragments. This breaking up of the original larger individuals is, as usual, 

 much more apparent in the quartz than in the felspar, and beautiful examples of 

 ' strain-shadows ' may frequently be seen in those quartz areas which have not 

 yielded altogether to the pressure. A further stage in the process is reached 

 when the sericitisation of the felspar has proceeded so far as to permit of the 

 ' shoving apart ' of the fragments by the various forces which have acted in 

 bringing about the degradation of the whole rock mass. This gradual decom- 

 position of the felspar and movement of the rock constituents can be perfectly 

 traced in the series of thin sections examined until the rock cannot be distinguished 

 from an ordinary arkose, while the arrangement on the large scale, and the more 

 or less parallel alignment of rounded and waterworn quartzose fragments amply 

 testify to the final assortment and rearrangement of the disintegrated material as 

 a result of ordinary sedimentation. 



The relations between this granite and arkose are of rather unusual scientific 

 interest, showing, as they do, the pre-Huronian existence of a basement or rtoor 

 upon which these sediments were laid down, and which in this portion at least 

 has escaped the movements to which the Laurentian gneisses have been subjected. 

 The granite is also somewhat different, both in composition and appearance, from 

 the granites and gneisses classified as Laurentian, and which are so frequently 

 referred to as the Fundamental Gneiss or Basement Complex, although during 

 recent years the assumption implied in these terms has been considerably weakened 

 •by the fact that the contact between such rocks and the associated elastics is, 

 wherever examined, one of intrusion. On the other hand, the composition of the 

 Huronian strata furnishes indubitable evidence of a pre-existing basement or floor 

 essentially granitic in composition, while the abundance of red granite pebbles and 

 fragments, which are so pre-eminently abundant in the breccio-conglomerate 

 lying at the base of the Huronian system, are very similar in composition and 

 appearance to the granite described above. This granite is, therefore, regarded 

 by the authors as the only instance at present known in which the material com- 

 posing the Huronian elastics can be clearly and directly traced, both macroscopi- 

 cally and microscopically, to the original source from which it has been derived. 



5. Report on the Irish Elk Remains in the Isle of Man. See Reports, p. .346. 



4. On some Nickeliferous Magnetites.'^ By Willet G. Miller. 



An examination has recently been made of the ore from some of the larger 

 •deposits of titaniferous magnetite in eastern Ontario. These magnetites have all 

 been found to be nickeliferous, the amount of nickel (and cobalt) present in some 

 being over 0-8 per cent. The non-titaniferous magnetites of the district have so 

 far as examined been found not to contain nickel. 



The titanium-nickel holding magnetites are considered to be of igneous origin, 

 while the other magnetites of the district are thought to be of aqueous or 

 mechanical origin. 



The fact that iron produced from titaniferous ores is of a very high quality 

 may have some connection with the occurrence of nickel in these ores. The 



' A short paper on this subject will appear in the next Annual Ecj)ort of the 

 Ontario Bureau of Mines, Toronto. 



