REPORT OF TEE CHIEF ASTRONOMER 241 



SESSIONAL PAPER No. 25a 



Kitchener and occasionally rusty beds are intercalated in the Creston series. 

 In both series the average rock is a quartzite, always micaceous and often 

 decidedly feldspathic Many of the strata above and below the Moyie sills have 

 a composition! essentially identical with that of typical Creston quartzite. 

 Hence the chemical analysis of this latter rock partly shows the constitution 

 of the sedimentary group invaded by the gabbro. From Mr. Schofield's descrip- 

 tion, the underlying Aldridge quartzite seems to be like the Kitchener. 



Professor Dittrich has analyzed such a type specimen collected several 

 miles to the westward of the Moyie river. It is very hard, light gray, 

 fine-grained to compact, and breaks with a subconchoidal fracture and sonor- 

 ous ring under the hammer. The hand-specimen shows glints of light reflected 

 from the cleavage-faces of minute feldspars scattered through the dominant 

 •quartz. A faint greenish hue is given to the rock by the disseminated mica. 

 This rock occurs in great thick-platy outcrops, the individual beds running 

 from a metre to three metres or more in thickness. Occasionally a notable 

 increase in dark mica and iron ore is seen in thin, darker-coloured intercala- 

 tions of silicious metargillite. 



In thin section this characteristic Creston quartzite is found to be chiefly 

 composed of quartz, feldspar, and mica, all interlocking in the manner usual 

 with such old sandstones. The clastic form of the mineral grains has been 

 largely lost through static metamorphism. The feldspars are orthoclase, micro- 

 aline, microperthite, oligoclase, and probably albite. The mica is biotite and 

 muscovite (possibly paragonite), the latter either well developed in plates or 

 occurring with shreddy, sericitic habit. The biotite is the more abundant of 

 the two micas. Subordinate constituents are titanite in anhedra, with less 

 abundant titaniferous magnetite and a few grains of epidote and zoisite. 



The chemical analysis (Table XIV., Col. 1) shows a notably high propor- 

 tion of alkalies, and therewith the importance of the feldspathic constituents, 

 especially of the albite molecule, which alone holds about 15 per cent of the 

 silica in combination. 



Table XIV. — Analyses of Sill Granite and Invaded Sediments. 



1. 



Si0 2 82-10 



Ti0 2 -40 



A1 2 3 8-86 



Fe 2 3 -49 



FeO 1-38 



MnO -03 



MgO -56 



CaO -82 



SrO 



Na 2 2-51 



K 2 2-41 



H 2 OatllO°C -05 



H 2 above 110°C -37 



C0 2 



P 2 O s -04 



100 02 



2. 



3. 



4. 



5. 



76-90 



74-23 



79-50 



72-05 



•35 



-58 



•38 



•63 



11-25 



13-23 



10-13 



11-88 



•69 



•84 



•59 



•83 



304 



2-65 



2-21 



4-87 



-02 



•07 



•02 



•12 



1-01 



1-02 



•78 



•85 



•88 



1-13 

 tr. 



•85 



2-10 



3-28 



2-78 



2-89 



2-20 



1-36 



2-66 



1-89 



2-66 



•20 



•08 



•12 



•10 



1-20 



•81 



•78 



1.21 



tr. 



•08 





•37 



•15 





•09 



•09 



100-33 



100-16 



100-23 



99-96 



Sp. gr. (corrected) . . . . 2-681 2-680 2-722 2-680 2-730 



35a — vol. ii — 16 



