470 EDWARD STEIDTMANN 



syenite with small amounts of hornblende, augite, and magnetite. 

 Several other syenite fades are represented, besides pegmatites, 

 small bodies of gabbro, granite, diorite, and later basic dikes. 



Lane^ presents a detailed description of the records of 17 drill 

 holes, placed along a line normal to the strike of the Keweenawan 

 copper-bearing rocks on Point Mamainse on the east shore of Lake 

 Superior. The copper-bearing series in this cross-section consist of 

 roughly parallel beds of conglomerate, apHte, and porphyrite 

 intruded by felsite. Their strike is about N. 10° W. and their dip 

 is from 20°-5o° west or lakeward. The beds are frequently offset 

 by dip faults. 



Leith^ states that the Algonkian, Nastapoka, and Richmond 

 groups, exposed on the east coast of Hudson Bay, consist of slightly 

 metamorphosed chemical and mechanical sediments, interbedded 

 with basic eruptives, with a seaward dip from 50° to 45°. The 

 Richmond group, unconformably, below the Nastapoka, embraces 

 coarse, ill-assorted mechanical sediments interbedded with basic 

 eruptives, generally dipping seaward at steeper angles than the 

 Nastapoka. The Nastapoka contains an iron formation containing 

 greenalite, iron carbonate, and derivative phases closely related to 

 extrusives. The Nastapoka is probably late Algonkian, perhaps 

 Animikie, because of its structural, stratigraphic, and metamorphic 

 similarity to the Animikie of the Lake Superior region. Leith 

 suggests that during the Algonkian, the Archaean protaxis may have 

 separated the Lake Superior geo-syncHne of deposition on the south 

 from a similar region of deposition on the north. 



Mickle^ finds that one hundred square miles of the Nipissing 

 region have numerous calcite veins, but that the metal-bearing 

 veins are restricted to ten square miles. On these ten square miles 

 there are about 2,000 calcite veins of which about i per cent are 

 metal-bearing, and only 66 veins were productive at the end of 

 1907. About 24 per cent of the area is underlaid by Huronian 



'A. C. Lane, "Diamond Drilling at Point Mamainse, Province of Ontario," 

 Canada Dept. of Mines, Bull. No. 6, 1911, 59 pp., i fig., i map, 5 pis. 



^C. K. Leith, "An Algonkian Basin in Hudson Bay," Econ. Geol., V, No. 3, 

 pp. 227-46. 



3 G. R. Mickle, "The Probable Number of Productive Veins in the Cobalt 

 District," Jour. Can. Min. Inst., XIII (1910), 325-35- 



