PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 629 



Amphibolyte. Greenstone.] 



No. 1009. AMPHIBOLYTE. 



From a dike that rises in the midst of the rocks NOB. 1004-1008: spreads and extends widely toward the east. 

 Ref. Annual Report, xv, pages 322, 323, 393. 



Meg. Greenstone of medium grain. 



Mir. (Ireen liornlleinle and chlorite make up a large part of this rock, probably 

 more than one-half. They are so cut by the feldspars that it is evident that they 

 'have taken the place of an ophitic pyroxene. The feldspars are twinned microliths, 

 much better preserved than those in rocks Nos. 1004 and 1005. There are occasional 

 areas of calcite and of pyrite, and numerous patches of leucoxene. There is no olivine 

 visible. A few apatite spicules pierce the feldspar. One section. 



Age. Archean (dike in Lower Keewatin). N. H. w. 



No. 1010. GREENSTONE (at contact ivith a dike). 



Contact between the fragmental rocks represented by Nos. 1002-1008 and the dike No. 1009. 

 Ref. Annual Report, xv, pages 323, 393. 



Meg. In the hand sample the two rocks are quite similar, the dike rock, 

 however, not being schistose. 



Mic. The slide contains a portion of the granular rock and a portion of the 

 igneous, but the latter is more altered than in No. 1009, and the feldspars are broken 

 by rock movements, and their fragments are dislodged. There is so much alteration 

 that no ophitic structure remains. The hornblende in general is not in distinct 

 crystals, but is broken into myriads of scattered grains, which, mingled with chlorite 

 and with leucoxene, give a confused and dirty aspect to the whole slide. One section. 



Age. Archean (Lower Keewatin). N. H. w. 



No. 1011. GREENSTONE. 



At various places between the lake shore (Fall lake) and the hill in S. E. % sec. 19, T. 63-11. 

 Ref. Annual Report, x, pages 324, 393. 



Meg. Green, medium grained, and ambiguous in character, structurally appears 

 to be in range of the rock that forms Kawasachong falls. 



Mic. The rock is essentially made up of green hornblende and t&bal&r feldspars, 

 the latter having such relation to the former as to suggest, though not prove, a 

 former ophitic structure in this rock, in that respect resembling rock No. 1009. 

 There is a,lso pennine, filling some large cavities. Epidoteand Icuco.rene are common. 

 These indicate an alteration of a basic igneous rock, and taken in connection with 

 the partial ophitic structure, rather favor that interpretation. Still, owing to the 

 uncertainty, the term greenstone is applied to this rock, a term which accommodates 

 either interpretation. Notwithstanding the great alteration there is no quartz. 



Age. Archean (Lower Keewatin). N. H. \v. 



