1 92 1. No. 8. 



0\ THE FXLOGITES OF NORWAY 



this rule. It will be useful, to compare what is known about the FeO: MgO 

 ratios in garnets and the other mafic minerals in labradorite-rocks and gab- 

 broic rocks. The following table will show these relations. 



Suselbakke, Mysen 

 Taato, Kragero . . . 

 Giving, Dybvaag. . 

 Meinkjaer, Bamle . 

 Kantalahti 



Hornblende 



FeC):MgO 



in liorn- 



blende etc. 



0.37 

 0.56 

 0.64 

 0.44 



I.]0 



FcOiMgO 

 in trarncts 



3. 10 

 4.60 

 2.07 

 2.52 

 5-41 



Garnet 



Aurlandsfjoi'd, Sogn . . . . 

 (Segregations) 



Alvaerstrommen, Bergen 

 Okken, Sogn 



Hornblende 



Olivine 

 Hyphersthene 

 Anthophyllite 



Diallage 



Hornblende 



0-37 

 0.3 r 



0-33 

 0.25 



0.23 

 0.31 

 0.31 



o.Ho 



0.95 



Garnet 



In all the rocks the garnet is the mineral by far richest in iron, but 

 while the FeO : MgO quotients in the garnets from the labradorite-rocks 

 are from 2.2 to 3.1 times higher than in the hornblende, they are from 3.4 

 to 8.5 times higher in the garnets of amphibolites and gabbros. Garnets 

 comparable with those in the labradorite rock may only be found in 

 the eclogites. 



The clinopyroxenes in the labradorite rocks are, as we have seen 

 above, highly aluminous, unlike the common diopsidic pyroxene, or "diallage", 

 in gabbros and amphibolites and similar to the clinopyroxenes in the 

 eclogites. 



No further discussion is necessary in this place. The facts presented 

 suffice to prove that the garnet in the labradorite-rocks and its 

 segregations does not contain any such high p i- o p o r t i o n of 

 iron ,as it does in the amphibolites and gabbros. As the 

 difference is not due to the chemical composition, it must be 

 a consequence of different physical conditions, and as the 

 garnet in labradorite-rocks shares the wide range of mutual 

 solid solutions of p y r o p e and a 1 m a n d i t c compounds only 

 with the eclogite-garnets, we conclude that the former have 

 originated under the same conditions, or in other words, the 

 earliest segregations and crystallizations in the labradorite- 

 rock belong to the eclogite facies; they are eclogites in 

 process of formation. 



