C URRENT PRE- CA MBRIA N LI TERA TURE 2 1 



Coleman makes notes on the petrology of Ontario, including the 

 Port Coldwell, Missanabie, and Wahnapitae areas. 1 



Coleman makes a third report on the gold region of western 

 Ontario. 2 



The districts visited and here reported upon are the Upper Seine 

 district, the Shoal Lake district, the Manitou district, the country 

 crossed between Manitou Lake and the Lake of the Woods, the Lake 

 of the Woods district, the West Shoal Lake district, the neighborhood 

 of Rat Portage, and the vicinity of Fort William on Lake Superior. 

 As in previous reports, the general geology worked out by Lawson for 

 the Lake of the Woods and Rainy Lake districts is accepted, and the 

 general principles applied to other districts of the region visited. 



In previous years it has been held that gold was to be looked for 

 only in the Huronian. During the past three years, however, it has 

 been found that some of the most promising gold deposits occur in 

 the granite or gneiss. It has also been found that the best veins, or 

 other ore deposits, occur at or near the contact of the Laurentian 

 eruptive rocks and the Huronian. 



In the Ontario region the gold deposits occur in the following 

 ways, (i) True fissure veins, commonly found in the areas of mas- 

 sive eruptive granite. (2) Lenticular or bedded veins, confined to 

 the schistose rocks. These are intercalated between the schists and 

 run parallel with their strike, and are not so continuous as the fissure 

 veins. (3) Contact deposits, between the Huronian and Laurentian. 

 These are rare in this district. (4) Fahlbands of schists, impregnated 

 with pyrites and other sulphides. (5) In quartz, associated with dikes 

 of porphyry or felsite, near the contact of the Huronian and Lauren- 

 tian rocks, penetrating the schists, and sometimes the granite itself. 

 (6) In an eruptive mass, in but one locality. (7) Placer deposits. 



Coleman 3 gives an interesting general account of the clastic 

 Huronian rojks of Western Ontario, in the region extending from the 

 Lake of the Woods in the west to Lac des Mille Lacs on the east, a 



1 Notes on the petrology of Ontario, by A. P. Coleman : Rept. Bureau of Mines, 

 Ontario, Vol. VI, 1898, pp. 145-150. 



2 Third report on the west Ontario gold region, by A. P. Coleman: Rept. 

 Bureau of Mines, Ontario, Vol. VI, 1897, PP- 71-124. 



3 Clastic Huronian rocks of Western Ontario, by A. P. Coleman : Rept. Bureau 

 of Mines, Ontario, Vol. VII, 1898, pp. 151-160. Published also in Bull. G. S. A. 

 Vol. IX, 1898, pp. 223-238. 



