DESCRIPTION OF THE AREAS 275 



banded with staurolite and garnet schists. The cyanite crystals stand out 

 in fan-shaped aggregates. Certain bands contain both cyanite and stau- 

 rolite, others contain staurolite and garnets, still others contain only one 

 of these minerals, and several bands consist of a white muscovite schist 

 with no other secondary silicates developed. 



In places narrow bands of the garnet- and staurolite-bearing schists 

 are conglomeratic, containing squeezed pebbles and boulders of quartz, 

 granite, and volcanic rocks. A few wider bands of conglomerate occur 

 in the area, some of which may possibly correspond to the Missian sedi- 

 ments of the Athapapuskow area. The matrix, however, is garnetiferous, 

 and no definite field evidence was found that any of them are infolded 

 sediments unconformably overlying the volcanic and schist rocks. On 

 the other hand, conglomerate is in places definitely interbanded with 

 rhyolite. Hence the whole is regarded as essentially one series. 



All these rocks are intruded by granite and pegmatite. In places the 

 secondary silicates in the older rocks appear to be a result of contact, and 

 in others of regional metamorphism. In several places they are abun- 

 dantly developed near granite stocks and the schistosity of the inclosing 

 rocks follows the contact, but in other places there is no adjacent intru- 

 sive, and yet the whole series is intensively metamorphosed. This seems 

 to be regional metamorphism. 



Of the intrusive rocks massive granite is more characteristic than the 

 well banded granite-gneisses. Eed and light gray are the prevailing 

 colors, although more basic, dark gray types are found locally, especially 

 along the borders of the intrusives. In texture, all phases from coarse to 

 fine-grained are found and porphyritic types locally occur along the bor- 

 ders of stocks. The composition varies from acid granite to diorite. 

 Biotite granite is the most common variety, but hornblende and horn- 

 blende-biotite types are also found. Pegmatite, lamprophyre, and aplite 

 dikes and quartz veins occur as late differentiates. 



CR088-PIPEST0NE AREA « 



Pipestone and Cross lakes are expansions of the Nelson Eiver, situated 

 approximately 60 miles north of the northern end of Lake "Winnipeg. 

 The pre-Cambrian rocks of the region consist of granite and granite- 

 gneiss intrusive into a complex of sedimentary and volcanic rocks and in 

 turn cut by gabbro and diabase dikes. The granite covers much the 

 greater part of the area, the older rocks being restricted to narrow fringes 

 along the shores of the lakes and to some of the islands. 



The volcanic members of the pre-granite complex are dominantly basic 



' F. .7. Alcock : Cross-Flpestone map area, Manitoba. Geol. Surv. Can., Sum. Rept., 

 1919. 



