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University of California. 



LVOL. I. 



lake only is there any doubt as to the position of the line of demar- 

 kation between the intrusive and intruded rocks. Along the north 

 shore of the lake and on the shores of the narrow arm which leads 

 to the outlet, the dip of the mica schists is to the N. N. W. away 

 from the intrusive mass at angles of about 6o°, but locally inclined 

 as high as 8o°. At the northeast corner of the lake, on the same 

 line of strike, the schists are vertical or dip somewhat toward the 

 mass. At the southwest end of the lake the schists are highly 

 garnetiferous and dip beneath the mass toward the northeast at 

 about 6o°. 



As will appear in the following pages, the intrusive mass is 

 petrographically distinct from the ordinary Lauren tian intrusives of 

 the region, and this fact, together with its limited extent, its isola- 

 tion in the midst of a schist belt, and the inward dip of the schists 

 at the southwest end of the lake, suggest with much probability 

 that it is laccolitic in its structural relations to the Coutchiching 

 nicks, the latter being without doubt metamorphic sediments. In 

 age the mass belongs to the Archaean in the same sense and for 

 the same reasons as do the granites and gneisses of the region 

 which are commonly referred to as Laurentian, and which have a 

 batholitic relation to the Ontarian rocks. 



This laccolitic mass, although very clearly a geological unit, is 

 not petrographically uniform. Three distinct types of rock may be 

 readily discriminated in the field, and each of these presents subor- 

 dinate variations. All three types have strongly-defined chemical 

 and mineralogical characters, which preclude their specific identifi- 

 cation with any other rocks known to the writer. In their struc- 

 ture, also, they present several features of exceptional interest. 

 While these rocks thus appear on chemical and mineralogical 

 grounds to be new types, they have a certain community of char- 

 acter which warrants their being grouped in a single family. To 

 designate this family, it is proposed to use the term Ma/ignite, from 

 the Maligne River, the chief stream of the immediate district in 

 which these rocks occur. 



The Malignites are characterized as basic, holocrystalline, plu- 

 tonic rocks, rich in alkalies and lime. Iron is present in but mod- 

 erate proportion for rocks of such basicity, and is practically wholly 



