AMPHIBOL1TI> \ND RELATED ROCKS-ST1U.U KLL. 263 



I 



II. GROUP IV. THE AMPHIBOLITKS AND ECLOOITKS. 



At Cape Denison the variety of types occurring in situ is considerably increased 

 by a study of specimens collected from the moraines. Tin- main occurrences in xitn 

 i (insist essentially of felspar and hornblende, with or without biotite. They have been 

 looked upon as basic igneous dykes which have recrystallised under conditions varying 

 from tlmse of Grubenmann's Meso zone to those of the Epi zone. The moraine types 

 include representatives of the Epi, Meso, and Kata divisions, and some are similar to 

 members of the Cape Gray series, occurring '2~> miles to the east. 



KATA DIVISION. 



The distinguishing feature of the Kata division of this group is the abundance 

 of pyroxene. A representative is specimen No. 937, a hornblende-plagioclase-pyroxene- 

 gneiss, which possesses similar features to the plagioclase-pyroxene-gneiss, No. 773, 

 from Cape Gray, and to the plagioclase-pyroxene-gneiss, No. 935, from Stillwell Island 1 . 

 Like Nos. 773 and 935, it possesses large relic crystals of augite, which have recrystallised 

 partly as clear granular pyroxene and partly as hornblende. Like No. 773, it possesses 

 traces of the original felspar laths of the original dolerite. Its felspar is a clear basic 

 labradorite, appearing partly as lath-shaped crystals, but mostly as coarse granular 

 crystals of the same average grain size as the hornblende and pyroxene. It contains a 

 few flakes of biotite and a few disseminated and minute grains of ilmenite. 



Related to this type are two erratics (Nos. 962 and 967), from Cape Hunter, 

 9 miles west of Cape Denison. These are hornblende-plagioclase-pyroxene-gneisses, in 

 which the pyroxene is in excess of the hornblende. Garnet is absent, and the pyroxene 

 includes both augite and hypersthene. Basic felspar is an important constituent, 

 and, in addition, the rocks carry a little biotite and accessory apatite and ilmenite. 



Numerous pink garnets are present in No. 595, a type closely related to the 

 garnet-plagioclase-pyroxene-gneiss, No. 935, from Stillwell Island. Some of the 

 garnets tend to form a zone between the pyroxene aggregates and the plagioclase. The 

 felspar occurs as large crystals of basic labradorite and as granulitic aggregates of a less 

 calcic felspar, probably andesine. Borne of the larger crystals contain cloudy alteration 

 products. Quartz is present, and has probably developed with the formation of garnet 

 by the interaction of felspar and pyroxene. There is a considerable amount of 

 hornblende, derived from the alteration of the pyroxene, which is associated with 

 numerous large grains of ilmenite, probably derived from the same source. This 

 garnet-bearing type is related to the eclogite family, but the clear omphacite of 

 the typical eclogite is absent. 



Specimen Xo. 227 is a dark, glistening schistose rock, showing abundant pink 

 garnet and black biotite in the hand specimen. It also possesses a thin lenticle of 

 segregated quartz along the schistosity, which may have developed with the formation 



1 Op. tit.. VV . 1W. 17*. 



