278 REGINALD E. HORE 



The rocks are seldom schistose except as the result 

 of contact metamorphism. 

 Great unconformity 

 Archean Laurentian: Igneous intrusives only. Holocrystalline light-colored 

 siliceous rocks. Chiefly granites, diorite, syenites, 

 and gneisses. 

 Igneous contact 

 Keewatin: Igneous and sedimentary rocks. All are much meta- 

 morphosed, and many schistose. 

 The relative age of the igneous and sedimentary rocks 

 is doubtful; but the iron formation is probably 

 younger than much of the igneous portion. The 

 agglomerates were probably contemporaneous with 

 some of the non-clastic volcanic rocks, and may be 

 contemporaneous with the other sediments. The 

 igneous rocks are chiefly of extrusive types. 

 Extrusives: (i) Dark-colored basic rocks — basalts — 

 mostly with composition and texture 

 of altered diabases. 

 (2) Light-colored siHceous rocks — fel- 

 sites and felsite porphyries — mostly 

 quartz porphyries which have been 

 altered to sericite schists. 

 Intrusives: (i) Basic rocks, mostly diabase and 

 gabbro. 

 (2) Siliceous rocks, mostly quartz por- 

 phyries and porphyrites. 

 Sediments: (i) The iron formation — chert, jasplite, 

 carbonates, slates, and green schists. 

 (2) Fragmental volcanic rocks — a grey 

 felsite agglomerate. 



