Analeite-Trachyte Tuffs and Breccias. 267 



General Geology of the District: 

 Mr. W. W. Leach, 1 who in the summer of 1902 examined 

 the Blairmore-Frank coal field, has, for descriptive purposes, 

 placed these pyroclastics at the top of the Middle and Lower 

 Cretaceous. Accompanying his report is a map showing the 

 distribution of these and other rocks in the district. The 

 volcanics have been traced in a north and south direction at 

 least twenty-four miles. The series attains a maximum thick- 

 ness of 1500 ft. and where exposed in one of the railway cuts 

 includes some igneous flows of augite-trachyte which contain a 

 great many inclusions similiar to the lava itself. Immediately 

 beneath the volcanics is a thickness of 1850 ft. of various 

 shales and sandstones, while overlying them are gray and 

 black shales and sandstones. The extremely important coal 

 measures of the region lie beneath the three formations just 

 mentioned, although some coal is found above them. 



The geological structure of the district is somewhat 

 complex, 2 much faulting and folding being in evidence so that 

 the same strata may outcrop two or three times in an east and 

 west cross-section. 



Minerals Found in the Tuffs and Breccias. 

 The specimens of the volcanics examined consist mostly 

 of crystal-tuffs and breccias, generally of a grayish green or 

 purplish color. The minerals are nearly always present in a 

 fragmentary condition showing rough, angular outlines, al- 

 though not infrequently the original crystal form has been 

 entirely preserved, and in other cases the rounded condition is 

 suggestive of water action. Only one of the specimens in the 

 collection shows, however, the result of water action in its 

 banded structure. 



The following minerals have been identified in the tuffs 

 and breccias : orthoclase, sanidine, analcite, augite, aegirite- 

 augite, aerigite, acmite, diopside, titanite, microcline, anortho- 

 clase, andesine, nephelite, hornblende, apatite, biotite, garnet, 

 magnetite and various secondary minerals, such as chlorite, 

 limonite, calcite, etc. Sodalite is probably present in small 

 quantities and possibly leucite. 



1. Summary Report Can. Geo. Survey 1902, p. 167. 



2. Leach, W. W. Summary Report Can. Geo. Survey 1902, p. 169. 



