64 PKNTTI ESKOLA. M.-N. Kl' 



crystallized within the j^nei.ss magma, hut more prohahlv 

 truc fragnicnts detached from larger hodies of eclogit 

 rocks. They have, however, oi'iginated under the same co"' 

 ditions as the gneiss and heen suhjected to stress durin'" 

 their cc) n s ol i d a t i o n, hereby pointing to a prr)bable genetic 

 connection, a consanguinity, to the latter. They are identical 

 i n b u 1 k c o m p o s i t i o n, a n a 1 o g o u s in the mode of occurrence 

 and, most probably, similar in the origin with t h t: "dark in- 

 clusions" so common in many granites and granitic gneisses. 



Eclo^iff in Gneiss in other Countries. 



In a pix'vious chapter were mentioned, from the literature of the 

 subject, several occurrences of eclogite directly connected with the olivine- 

 rocks. Here it will be useful to give a review of the occurrences enclosed 

 in gneissic rocks. 



Perhaps the best-known eclogite-bearing gneiss mass is that of Münch- 

 berg in the Bavarian Fichtelgebirge. It is one of those batholiths 

 in Central Europe ibrmerly regarded as belonging to the pre-Cambrian 

 "Grundgebirge", but later found to be intrusive in the paleozoic sedimentary 

 series, as at first was emphasized by C. F. Naumann'. The Munchberg 

 eclogites were investigated petrologically by Ernst Dull-, his field and 

 microscopic studies being the most careful and detailed so far published 

 about any eclogite-bearing area. 



The Munchberg eclogite occurs, at very numerous places, as lenses in 

 the gneiss, its outer appearance and parting recalling igneous rocks. All 

 the lenses are surrounded b}- amphibolitic zones, interpreted by Dull as 

 originated by the alteration of the eclogite. Some resorption has taken 

 place on the boundaries, and smaller inclusions have been entirely resorbed 

 giving rise to schlieric hornblende- and mica-gneiss. The resorption bands 

 are elongated in the strike. Banding in the eclogite often occurs due to 

 unequal distribution of garnet and pyroxene. In all these characters a 

 perfect similarity to the Norwegian occurrences is evident. 



Dull distinguishes between orthogneiss and paragneiss, but the latter, 

 in his nomenclature, is simply an igneous gneiss containing appreciable 

 amounts of resorbed materials. It is not a sedimentogenous gneiss. 



Besides eclogite the Munchberg gneiss also contains inclusions and 

 larger masses of amphibolite. 



Mineralogically the Münchberg eclogites differ from the Norwegian 

 rocks in containing cyanite. The other constituents are the same. 



' C. F. Naumann, Ueber die Munchberger Gneissbildung. N. Jahrb. Min. etc. 1863, p. 1. 

 2 Ernst Dull, Ueber die Eklogite des Munchberger Gneissgebietes. Geognostische Jahres- 

 hefte, 15, 1902. 



