REPORT OF TEE CHIEF ASTRONOMER 435 



SESSIONAL PAPER No. 25a 



within, a single body. Though transitions seemed to appear in the actual out- 

 crops, the search for final evidence in these rocks, crushed and obscured as they 

 are, has so far proved unavailing. Analogous occurrences in other parts of th© 

 Boundary belt suggest that the gabbro and olivine rock were intruded at different 

 dates. 



Ashnola Gabbro. 



Throughout its five miles of length (Figure 32) the Ashnola gabbro body 

 is homogeneous in composition, but often varies abruptly in grain from medium 

 to quite coarse. The colour is uniformly a peculiar deep fawn, which is the 

 dominating tint of the feldspar. This colour is rather remarkable, as the rock 

 proves under the, microscope to be quite fresh, with feldspars of glassy clear- 

 ness. The essential constituents are a green augite, often colourless in thin 

 section, brownish-green hornblende, brown biotite, and labradorite, Ab 5 An s , 

 Abundant apatite, some magnetite (probably titaniferous), and a very little 

 interstitial quartz are the accessories. The structure in the original rock is the- 

 hypidiomorphic-granular, though the augite is often, especially in the coarser 

 grained phases, poikilitic. Regular intergrowths of the augite and hornblende 

 are common. 



A fresh type specimen (No. 1403). taken near the contact with the Rename! 

 granite about three hundred yards north of the Boundary line, has been analyzed - 

 by Mr. Connor, with the following result : — 



Analysis of Ashnola gabbro. 



Mol. - 



SiOo 47-76 -796 



TiO 2-20 -028 



AljA 18-58 -182 



FeA 2-19 -014 



Pea. 9-39 -131 



MnO «29 -0U 



MgO 4-15 -1M 



CaO ■. 9-39 .168- 



SrO -03 



BaO -02 



Xa.0 3-61 -058 



K 2 -47. -005 



BLO at 105°C -12 



HlO 'above 105°C -53 



P„0, -78 -006 



99-51 



Sp.gr ' 2-957 



25a— vol. ii— 28* 



