76 Transactions. 



tion of the rock is too intense to determine whether this con- 

 stituent is original, but it was at least introduced prior to the 

 dynamic metamorphism of the schist, the large size of the indi- 

 viduals being the result of recystallization during metamor- 

 phism. 



Type No. 2 (Plate XII, 3a) is less schistose, and preserves 

 more of its original structure. It is composed of a mass of 

 labradorite and quartz crystals thickly grouped, the interspaces 

 being occupied by fibres of chlorite, a good deal of calcite and 

 epidote, with rutile plentiful and magnetite accessory. The 

 feldspars are roughly rectangular, and simple or once twinned. 

 The absence of polysynthetic twinning indicates secondary 

 recrystallization. Both feldspars and quartz are crowded with 

 crystals of epidote having a marked centric arrangement. The 

 rock is practically a feldspar-schist. 



The specific gravity of these rocks varies from 2-9 to 3-2. 



Conclusions. 



Judging from the above lines of evidence, there is no doubt 

 that the schists described are altered flows or sheets of basic 

 igneous rocks, contemporaneous with the associated mica-schists 

 of sedimentary origin. 



4. Igneous Intrusions. 

 The So-called Porphyrites of the Carrick Range. 



Both Hutton and Ulrich refer, in their " Geology and Gold- 

 fields of Otago," to dykes of porphyrite, or hornstone-porphyry, 

 on the Carrick Range, in the vicinity of the Carrick reefs.* 

 Careful examination failed to locate these dykes, and I can only 

 conclude that both these authorities have been misled into call- 

 ing dykes some outcrops of dark iron-stained gossan near old 

 Carricktown. These have frequently a brecciated structure, 

 and the resulting appearance resembles a porphyritic rock with 

 phenocrysts of quartz. The outcrops are, however, simply the 

 barren caps of lodes. 



Two magnesian dykes occur in Central Otago which were 

 unknown to Hutton, and which have not been hitherto de- 

 scribed. 



Gibbston Dyke. 



This occurs across the Kawarau River from Gibbston, about 

 half a mile up the left branch of the Springburn, a tributary 

 of the Gentle Annie. The schist in the neighbourhood of the 

 intrusion has been highly crushed and disturbed. The dyke 



* Hutton and Ulrioli, " Geology of Otago " (Dunidin, 1875), pp. 31 and 157. 



