REVIEWS 57 



A. P. Coleman. "The Sudbury Nickel Deposits." Report of the Bureau 



of Mines, Ontario, 1903, pp. 235-303, 



Coleman describes and maps the nickel deposits near Sudbury, Ontario, and 

 incidentally discusses the geology of the region. The probable succession and age of 

 the rocks of the district is as follows, in ascending order : 



! Dikes of diabase. 

 Younger Granite. 

 Nickel-bearing eruptive; norite; micropegmatite ; granite. 

 Animikie(?) or Upper Huronian (?) — Oval area of tuffs, sandstones, and slates 



overlying the preceding. 

 Laurentian. — Granitoid gneiss. 



K Green schists and greenstones. 



Upper Huronian •{ ^ 1 * -^ j 1 



*^^ / Arkoses, quartzites, and graywackes 



It can hardly be said that the precise age of any of these groups of rocks is 

 known, though they probably range from the base of the Upper Huronian to the 

 Keweenawan, including the Laurentian as later than the Upper Huronian. No rocks 

 undoubtedly of Lower Huronian age are known from the nickel district proper ; 

 though the ranges of banded silica and magnetite extending through Hutton and 

 Wisner townships to the north of the nickel area evidently belong to the Lower 

 Huronian.' The latter rocks occur entirely inclosed, so far as known, in granites and 

 gneisses, generally considered Laurentian, and have not been found in direct connec- 

 tion with the rocks here described. 



The fact has been brought out that all of the nickel deposits are either on the 

 basic edge of a great eruptive band, which at the opposite edge becomes a quartz 

 syenite or granite, or in dike-like offshoots, often, however, interrupted by other rocks 

 projecting from the southeastern basic edge of the great gabbro band. This band 

 has been found to outcrop in a great oval, the north and south sides of which have 

 been known respectively as the North and South nickel ranges. The structure is 

 synclinal, and the center is occupied by Animikie or Upper Huronian rocks. 



There are two different types of deposits represented in the mines of the district : 

 those along the southeastern margin of the main range, often crowded into bay-like 

 indentations of the adjoining rock ; and those strung out along the narrow off-shoots 

 from the main range, as Peters suggests, "like sausages on a string, but with a long 

 piece of string between the sausages."^ Among the former class are the Creighton, 

 Gertrude, Elsie, Murray, and Blezard mines; among the latter, the Copper Cliff, 

 Evans, Frood and Stobie, and the Victoria and Worthington mines. Perhaps a third 

 variety should be distinguished for the Vermilion mine, which contains rich nickel and 

 copper ores, but has no visible association with a band of gabbro, having, however, 

 been formed probably by hot circulating fluids proceeding from such a band. 



The final impression left is that the marginal type of deposit is in the main 

 of plutonic origin, aqueous work being relatively unimportant; that in the offset 

 type plutonic is generally more important than aqueous action, though one example, 

 that of the Worthington, suggests more complete rearrangement of the materials by 

 circulating water ; thus forming a transition to ordinary vein deposits wholly due to 

 water action, as at the Vermilion mine. 



^Report of the Bureau of Mines, 1901, p. 186. 



^ Mineral Resources of Ontario, 1^. 104. 



