AMI'HIIUiUTKS AND RELATED !!<>< K- >TI l.l.\\ KM.. 201 



-'. Mj.i Division 277 



_'"i7, (pid.itv-fi'lHpar-sclmt. 

 N l.'iT. :>22, .piilote-felspar-sehi-.t with broader banding than No. 257, and containing a little quutt? 



72fl, epidote-fe|gpar-Hchil with very broad hands of felspar and epidotr. 

 NM. 398, epidote-felspar rork with large porphyroblaU of microcline. 

 N.I. 954, chlorite-raicriK-lme-gncisH. belonging to the group of the alkali-felspar gnei* 

 No. 590, epidote-fclsp.u -. lu.i with pink purphyrobliuits or augen of febtpar. 

 No. 910, epidote-frlmir breccia, in which i'|>idnt>- nccum in a finely -granular form. 



.'._'. i'pi<l.iUj-fel.par-gneis, brerri:<ti>cl l,y vein* of quartz and felspar and finely-granular cpidote. 



591, epidote-fclspar-Kneiss in whii-h tin- tine granular epidote occurs in wavy band* producing a helicnl 

 structure. 



No. 589, epidotc-fcUpar-gneiiU) in win. h >-pi<l..t< i> m.>n- abundant than No. 591. 



V'. ">!!>. epidote i-hlorite-HchiHt containinu more chlorite and less felspar than No. 589. 



No. 255, an epidocita of Group IX which results when there is a deficiency of both chlorite and felspar. 



V. Description of Plates 280 



I. INTRODUCTION. 



I'.KAT variety of metamorphic rocks were collected from the moraines at Cape 

 Di-nison, in Adelie Land, and the following notes give some account of the amphibolites 

 ;in<l related rocks. Three specimens, which are specifically mentioned, are fragments 

 nl initii s found at Cape Hunter, nine miles west of Cape Denison. The basis of the 

 grouping of these rocks is Grubenmann's chemical classification, with its zonal 

 subdivisions, and this section includes Groups IV, V, and III, the Amphibolites and 

 Kclogites, the Magnesium Silicate Gneisses, and the Plagioclase Gneisses. Each group 

 is subdivided into three divisions (based on mineral composition and on structure) 

 rjilli'd the Kata, Meso, and Epi divisions. In the Kata division of these groups the 

 pyroxene is in excess of the hornblende; in the Meso division the hornblende i> 

 in excess of the pyroxene ; and in the Epi division there is a pronounced development 

 of saussurite, lawsonite, epidote or chlorite, and also of mechanical structures. These 

 groups are defined by their chemical composition, and the use of the classification is 

 therefore restricted by the absence of complete chemical analyses. The chemical 

 (imposition is, however, reflected in the mineral composition, from which the divisions 

 nl '-;ich group have been in most cases recognised. 



The term amphibolitr is used with the same meaning adopted in the memoir 

 mi the metamorphio rocks occurring in situ at Cape Denison. 1 It may be defined as 

 u completely recrystallised rock of basic igneous chemical composition, whose mineral 

 content is essentially hornblende and plagioclase. The latter mineral can be replaced 

 wholly or partly by other minerals, such as zoisite, epidote, garnet, or scapolite. When 

 tin- amphibolite possesses a strongly-foliated character it has been called an 

 (iin/ihibolite-schist. In many cases the schistose structure is accentuated by the partial 

 replacement of hornblende by biotite or chlorite, and the term ainphibolit 

 becomes equivalent to the terms biotite, chlorite or tnica-amphibolite. 



' " MUmorphic IWLi of .Hrlie Land." F. L SUIlwrll. S< imtitk RporU, A.A.E , Vol. iii, pt. 1, pp. 24, 26. 



