1S2 11. I*, ciisirixd — Ar(ii'j'K-sYi<:Nrri'; (jxkiss ni<:ak i.oox j.akk 



(Quartz occurs only sparingly in this rock, tliough very (juartzose 

 phases api)ear elsewliere in the Loon Fjake vicinity. It is niainl}^ in 

 rather large, elongated, cylindrical individuals. The elongation seems 

 to be effected rather by solution and recrystallization than by crushing. 

 The individuals are either entire or made U[) of but few fragments, and 

 the fine granulation which must have l)een produced b}^ the crushing 

 process is nowhere in evidence. In the quartzose varieties the ferro- 

 magnesian silicates recede with disap[)earance of the foliation, its {)lace 

 being taken by a linear structure produced l)y the elongated quartzes. 



Some quartz is also found as inclusions in the feldspar, sometimes 

 rather numerously and with a tendency to micrographic growths. There 

 is also a small amount of interstitial quartz and orthoclase, which seems 

 secondary. 



►Structure of the Rocks 



These rocks have a cataclastic structure. In the gneissoid rock, from 

 the third cut the granulation is pretty complete, but even there occa- 

 sional larger nuclei remain and show undulatory extinction. In the 

 coarser rock, from the first cut many such large fragments are found, 

 constituting more than half the rock. The Diana rock shows the struc- 

 ture even better. Precisely the same variations in degree of granulation 

 are to be found that the anorthosites exhibit, except for the lack of the 

 very coarse varieties in the syenite, such as make up a considerable part 

 of the anorthosite, but this is regarded as an original difference. In 

 addition to the cataclastic structure, the rock is nearly everywhere 

 foliated. 



Chemical Analyses 



table of analyses 



These syenites are so variable in mineral content and their field rela- 

 tions to other rocks, which on the one hand are much more acid and on 

 the other more basicj and into which thev apparently grade, are 3'et so 

 uncertain that a large amount of chemical work will be necessary' in order 

 to fully elucidate the }>roblems suggested. Onl}^ a beginning has been 

 made in this, which, however, suffices to show the character of the typical 

 rock and to permit of a certain amount of discussion and comparison 

 with other syenites. 



