472 EDWARD STEIDTMANN 



quartz, with small amounts of calcite and siderite. Sulphides of 

 copper, lead, zinc, and iron are also present. 



Moore' states that the rocks at Round Lake north of Lake 

 Nipigon are Keewatin ellipsoidal greenstone, green schist, fine- 

 grained quartose gneiss, and lean, magnetic, cherty iron formation, 

 intruded by Laurentian granite and gneiss. The Archaean complex 

 is intruded by Keweenawan diabase. The iron formation is 

 separated from the greenstones by schists and sediments. It con- 

 sists of bands of crystallized chert, magnetite, hematite, and some 

 siderite. 



Moore^ states that the pre-Cambrian rocks of the Lake Savant 

 Area northwest of Lake Nipigon belong to the Keewatin, Lauren- 

 tian, Huronian, and possibly Keweenawan systems. The Keewatin 

 comprises acid, intermediate, and basic extrusives and intrusives, 

 banded magnetic, cherty iron formation, and an unusual develop- 

 ment of sediments in the form of graywacke and gray gneiss. The 

 Laurentian consists of granites arid gneisses intrusive into the 

 Keewatin. The rocks of the Huronian are principally conglomer- 

 ates, graywacke, and a little quartzite. A few basic dikes may be 

 of Keweenawan age, 



Moore^ describes the pyrite deposits of Big Vermilion Lake near 

 the Minnesota boundary. The pre-Cambrian rocks of this region 

 include a basement of intrusive and extrusive acid and basic rocks, 

 overlaid by cherty iron formation, graphitic slate, graywacke, 

 arkose and quartzite. The two systems were intruded by granite. 

 The pyrite occurs in fissure veins in greenstone, quartz porphyry, 

 and iron formation. 



Moore"" states that the Onaman Iron Range district covers about 

 70 square miles and lies between 45 and 50 miles up the Red Paint 

 River, northeast of Lake Nipigon. The Keewatin, Laurentian, 



' E. S. Moore, "Iron Range North of Round Lake," Onl. Bur. of Mines, i8th 

 Ann. Kept., XVIII, Pt. i, pp. 154-62. 



^ E. S. Moore, "Lake Savant Iron Range," Out. Bur. Mines, igth Ann. Rept., 

 XIX (1910), Pt. I, pp. 173-93, 16 figs. 



sE. S. Moore, "Vermilion Lake Pyrite Deposits," Ont. Bur. Mines, 20th Ann. 

 RepL, 191 1, pp. 199-208, figs. 6, I map. 



^ E. S. Moore, " Geology of Onaman Iron Ranges Area," Oni. Bur. of Mines, Attn. 

 Kept., XVIII (1909), Pt. I, pp. 196-253, 22 figs., 3 pis., I map. 



