BY M. AUROUSSEAU. 265' 



Miciogranite. 

 Porphyritic granodiorite. 

 Gneiss. 



They comprise, in all, a fundamental gneiss, and igneous rocks 

 belonging to at least two, perhaps to three periods of activity. 



The gneiss and granodiorite are very much alike in appearance, 

 especially when weathered, which is probably the cause of their 

 not having been separated before. Their boundary, likewise, 

 appears to be a very complicated and irregular one. 



The Gneiss is variable, but generally coarse, and porphyritic 

 with felspar. It forms part of the mass of Mt. Clarence, and 

 Mt. Adelaide. At the south end of Middleton Beach, the folia 

 strike at 272° prismatic, a trend which is maintained elsewhere. 

 Between Mts. Clarence and Adelaide is a contorted zone, where 

 it becomes garnetiferous, finer in grain, more irregular in com- 

 position, and contains dark schlieren. This zone is well exposed 

 at the timber-yai'd between the deepwater- and town-jetties. 

 Further south, near the entrance-beacon, a junction with grano- 

 diorite is exposed. 



The Porphyritic Granodiorite forms the bulk of Mt. Melville, 

 and part of Mt. Clarence, and occurs also as dykes in the gneiss. 

 It is remarkably like the Roelands rock, but its large felspar- 

 phenocrysts are generally fluidally arranged along different 

 directions. It weathers into large, characteristic tors, which 

 are a feature in the scenery of the district. Two very fresh 

 dykes, exactly like the main rock, cut the gneiss on the coast, 

 about one-quarter of a mile south of the south end of Middleton 

 Beach. They are each a foot wide, and ultimately run together. 

 They are cut and faulted by a small vein of microgranite. 



The Alicrog rani te occurs as dykes and veins in the granodiorite 

 and gneiss. It is well exposed on the bare Hanks of Mt. Melville, 

 and one large dyke runs from the summit of Mt. Clarence down 

 through the reservoir. It sometimes contains large felspar- 

 xenocrvsts. At a quarry on a bend of the Middleton Road, it 

 is closely associated with a coarse, epidotic biotite-pegmatite, 

 and is elsewhere bordered by pegmatite. 



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