374 DEPARTMENT OF TEE INTERIOR 



2 GEORGE V, A. 1912 



minette, kersantite, odinite, spessartite, and vogesite cut the monzonite and 

 ' augite porphyrite ' at Rossland, where the mica-lamprophyres are of two ages, 

 separated by a period of ore-formation. 



19. The Rossland monzonite cuts the older (andesitic) members of the 

 Rossland volcanic group. The monzonite is cut by intrusives lithologically 

 identical with the Coryell syenite and by dikes of alkaline syenite porphyry 

 (probably equivalent to the biotite-augite syenite porphyry mentioned under 

 '*!'). McConnell, Brock, and Young consider that the granite cutting the 

 Rossland monzonite is equivalent to the Trail (" Nelson " or " Older ") 

 granodiorite. 



20. The peculiar porphyritic (facetted) olivine syenite forms small irregu- 

 lar masses cutting the older members of the Rossland volcanic group and the 

 still older Sutherland schists. 



21. Some evidence on age relations may be derived from the amount of 

 crushing and dynamic metamorphism suffered by each of the different forma- 

 tions. The observed facts may be here summarized. 



The sedimentaries of the Rossland mountains are all strongly deformed; 

 in nearly all of the bodies high to vertical dips have been measured. The Pend 

 D'Oreille group of rocks, the Sutherland complex, and the fossiliferous lime- 

 stone-chert-quartzite series in Little Sheep creek valley are mashed and intensely 

 metamorphosed. The plant bearing (Cretaceous?) argillites and sandstones 

 in Little Sheep creek valley are crumpled and faulted greatly but are not much 

 metamorphosed. The Sophie mountain conglomerate has been energetically 

 upturned but is not much metamorphosed at any observed point. The other 

 bodies of conglomerate show lower dips and an induration of about the same 

 order as those seen at Sophie mountain. The Beaver Mountain sediments show 

 dips rarely surpassing 50° and are not metamorphosed beyond the point of 

 decided induration. 



The eruptives may be divided into three classes according to the amount 

 of crushing and metamorphism effected in each body, the evidences being con- 

 trolled by microscopic examinations. 



The greenstones of the Pend D'Oreille and Rossland volcanic groups and 

 the biotite-granite stock east of Cascade have been intimately crushed and 

 largely recrystallized. 



The second class, representing bodies which have been sheared only locally 

 and are little metamorphosed, includes many of the andesites and basalts of 

 the Rossland group; the Fife and Baker gabbros, the Rossland monzonite and 

 latites (rarely sheared) ; the Beaver Mountain volcanics (very rarely sheared) ; 

 the Trail batholith (often strained) ; the Sheppard granite (very rarely sheared 

 or strained) ; some of the minettes and other lamprophyres. 



The third class includes bodies which are not noticeably (in field or labor- 

 atory) crushed, strained, or metamorphosed dynamically. These are: the 

 Coryell syenite and the dikes cutting it (biotite-augite syenite porphyry, 

 biotite granite porphyry, aplite, missourite) ; many minettes and other lampro- 

 phyres; the porphyritic olivine syenite. 



