CHAPTER XXI 



THE VOLCANIC ROCKS OF VANUA LEVU (continued) 



ACID ANDESITES 

 Previous observations on the Hornblende- Andesites of Fiji 



THESE rocks were first described by Wichmann x from specimens 

 obtained by Kleinschmidt from the mountain of Mbuke Levu in 

 Kandavu. These Kandavu rocks had a microfelsitic base, the 

 porphyritic brown hornblende having usually black borders in 

 which a change into epidote was observed. Rhombic pyroxene 

 was only noted as an occasional constituent of a rock from Ono. 

 Renard 2 described these rocks from the vicinity of Ngaloa 

 Harbour in Kandavu and remarked that bronzite was of more 

 common occurrence than the monoclinic pyroxene. In the ground- 

 mass were numerous felspar and augite microliths, whilst there was 

 a porphyritic development of plagioclase, hornblende, biotite, and 

 pyroxene. The hornblende phenocrysts played an important part 

 in the rock-composition, being surrounded by a black zone of 

 magnetite or bordered by a bacillary aggregate of small pyroxene 

 prisms, parallel and colourless or greenish, with extinction-angles of 

 40. There was often also a development of biotite in the heart of 

 the mineral, the whole hornblende section being sometimes thus 

 transformed. 



Mr. Eakle 3 has more recently described the hornblende-andesites 

 from Mbuke Levu in Kandavu. As the result of his examination 

 of a collection of volcanic rocks made by the Agassiz expedition in 



1 Petrographie des Viti Archipelsj Miner, und Petrogr. Mittheil ; band v, 

 heft i,Wien, 1882. 



2 Physics and Chemistry, II. Report Scient. Results; H.M.S. Challenger \ 

 London, 1889. 



3 Petro graphical Notes on the Fiji Islands; Proceed. Amer. Acad. Arts and 

 Sciences ; vol. 34 ; no. 21 ; May, 1899. 



