264 TOE MARQUETTE IROX-BEARIXG DISTRICT. 



have a quartzite base. The complex fraii-nients found in the congkimer- 

 ates in each hicahty are predominantly of the particular rock immediately 

 subjacent, but with these are fragments derived from other sources. 

 These fragments comprise white mashed granite, described on -p. 220 

 as sericitic (luartz-schist; white mashed granite containing large crystals 

 of feldspar; pink granite; gneissoid granite; a peculiar, very feldspathic 

 pegmatite; fine-grained chloritic schist or gneiss; sericite-schist or gneiss; 

 quartz pebbles; and other varieties of rock. All of these pebbles show 

 dynamic eifects. Many of them have been broken and cemented by 

 finely crystalline and secondary quartz. Microcline cleavage is also 

 developed in the potash-feldspars. The quartz grains uniformly show 

 undulatory extinction; many of them are distinctly fractured, and these 

 fractures are in some grains according to a rectangular system. The quartz 

 pebbles are found to consist of intricately interlocking or closely fitting, 

 roundish granules of quartz, but in no case do any of these distinctly show 

 a fragmental character, and they are lielieved to have been derived from 

 granite or from vein quartz. The chloritic and sericitic schists and gneisses 

 have in some cases, at first glance, a fragmental appearance, but the more 

 closely they are studied the more do they appear to be completely crys- 

 talline rocks. To desci'ibe the fragments of the conglomerates in detail 

 would be a repetition of the description of the rocks of the Basement 

 Complex. 



The quartzite or quartzite ]:)ackground of the conglomerates contains 

 an abundant, very finelv crystalline grouudmass of sericite, kaolin, and 

 quartz, with a little chlorite, and is often impregnated with iron oxide. In 

 this groundmass are simple and complex grains of quartz and less abundant 

 grains of the various feldspars, and as the rocks become coarser-grained 

 these pass into the complex areas composed of (piartz and feldspar. The 

 groundmass of these rocks and that of the fragments contained in them 

 are the same, and the structure is somewhat similar to the mashed gneissoid 

 granites or sei-icitic quartz-schists of the Archean. (See p. 220.) Also, 

 man-\' of the simple and complex quartz grain.s have a granitic appearance, 

 having been but little waterworn; but some of the grains show a distinct 

 waterworn character, and they are rarel}" enlarged. In the quartzites 



