GEOLOGY OF THE PARADOX LAKE QUADRANGLE 499 



show their characteristic irridescence and are an inch or more in 

 length. Farther south and east, along a zone beginning a few miles 

 from the border of the intrusion, the rock is granulated and a cata- 

 clastic structure is seen in thin section. If present, the bisilicates 

 are drawn out into irregular bands. If slightly more crushed the 

 rock becomes a gneiss, and as the granulated labradorite is white, it 

 becomes a matter of some difficulty to distinguish in hand specimens 

 between gneissic anorthosite and the sedimentary gneiss. It was 

 this banding which led Emmons to claim a sedimentary origin for 

 the rock. The extreme of metamorphism is seen in a complete 

 mashing and the development of new minerals. On the hill north- 

 west of Paradox lake is a variety which in the hand specimen is an 

 even white color, with no constituent minerals distinguishable, and 

 with large secondary garnets embedded in the white mass. In thin 

 section this white rock is found to consist of broken pieces of plagio- 

 clase, and in general the whiter the rock the more complete the 

 granulation. The completely granulated rock resembles a massive 

 limestone. If ferro-magnesian minerals are present they may be 

 drawn out into gneissic bands with a cataclastic structure. Garnet, 

 secondary after pyroxene, often occurs. These intensely granulated 

 anorthosites frequently contain titaniferous iron ore. Prof. Frank 

 D. Adams 1 has suggested that these ore bodies may be due to a 

 gathering together, from crushing, of minute inclusions previously 

 contained in the feldspar. The area in Canada which he describes 

 is remarkably similar to the one under consideration, but the Adiron- 

 dack area does not contain such an extensive amount of black dust 

 in its labradorite. Titaniferous magnetite occurs in occasional crys- 

 tals in the massive anorthosite, and its formation appears to be that 

 of a local gathering together of constituents analogous to that of the 

 grouping of the bisilicates. The dark silicates are more abundant 

 in the peripheral portion of the intrusion. 



The irregularities in size of grain and in distribution of constitu- 

 ents must be due to processes taking place during consolidation. 

 Whether the processes are chemical in their nature or physical, or 



*F. D. Adams. Geol. Survey of Canada; Rept J. 1895. v. 8. 



