[TYRRELL] PRE-CAMBRIAN GOLDFIELDS OF CENTRAL CANADA 97 



one place in this latter schist there was a vein or band of almost massive 

 arsenopyrite, which in places on the surface was oxidised to green 

 earthy Scorodite. 



On the Palace and adjoining claims, which lie a short distance to 

 the eastward of those already mentioned, the rock is a light green 

 schistose feldspar porphyry, in which phenocrysts of plagioclase, 

 usually much decomposed and with ragged edges, lie in a fine-grained 

 groundmass of feldspar and chlorite. Sometimes quartz is present, 

 both as phenocrysts and in the crystalline matrix. 



The schists and porphyries here described are doubtless of Keewatin 

 age, but whether the gold-bearing veins belong to a later stage of the 

 Archaean or not was not determined. 



It is interesting to note here that Mr. Bruce, of the Geological 

 Survey of Canada, who examined this district in the summer of 1914, 

 and whose brief report appeared in July 1915, records the occurrence 

 on Beaver Lake of some bands of conglomerate, similar to those 

 elsewhere referred to the Temiskamian, folded in with greenstones, 

 etc., which at no great distance are cut by gold-bearing veins. This 

 would indicate that the veins, which were formed subsequent to the 

 folding of the rocks, were later in age than the conglomerates. 



Long Lake. Gold also occurs associated with arsenopyrite at 

 Long Lake about 25 miles south-west of Sudbury in rocks of Temis- 

 kamian age cut by basic intrusions probably of Algoman age. 



^ Dr. Coleman describes the gold ore and rocks associated with it 

 as follows : 



"On the road south of the (Long) lake the (Temiskamian) quartz- 

 ite is still more disturbed, and is cut by dykes of coarse-grained and 

 also of fine-grained diorite. Presently one observes that large blocks 

 of the quartzite are enclosed in the diorite and are somewhat meta- 

 morphosed and penetrated by many small quartz veins. The mine 

 itself is on such a mass of quartzite, a large irregular block enclosed in 

 the diorite, part of it still showing bedding and cross bedding. In thin 

 sections of the ore one finds the quartz crushed and rolled out and 

 accompanied by some plagioclase, the whole evidently a good deal 

 recrystallised, since no original grains can be seen. The diorite is 

 rather dark greenish-grey and consists mainly of plagioclase and horn- 

 blende, with some biotite, epidote and apatite." 



"The ore of the Long Lake mine is of an unusual character, con- 

 sisting simply of the quartzite impregnated with mispickel, and in part 

 also with pyrite. The mispickel is seldom in crystals visible to the 

 eye, but is often diffused in small particles, giving a bluish tinge to the 



1 A. P. Coleman. The Pre-Cambrian Rocks north of Lake Huron. 23rd Ann. 

 Rep. Ont. Bur. Min. 1914, p. 218. 



