52 president's address — section c. 



TJie Crystalline Coinplexes. 



In the more recent statements of the history of New Zealand, it 

 has been customary to consider as of Cambrian or pre-Cambrian age 

 the complex of gniesses and associated rocks in the south-western 

 extremity of New Zealand, "Fiordland." but the evidence offered 

 for this has not been conclusive. Hector (1886) was inclined to 

 divide this complex into two portions, recognising an ancient group 

 of gneisses, with a younger series of granites, syenite, diorite, &c. , 

 which invaded and metamorphosed a group of possibly Devonian 

 sediments and basic igneous rocks, ccnverting them intoi micaceous 

 and hcrnblendic schists.* Hutton (1900) suggested the dioritic 

 mtrusicns were contemporaneous with the outpouring of the Te 

 Anau basic breccias, supposed to be Carboniferous, and Speight 

 (1910) thought they might be as young as the latter part of the 

 Meso'Zoic period. In the north-west of the South Island (Colling- 

 wood), gneiss and schists occur which have been variously con- 

 sidered as portion of a single Silurian series, or cif a conformable 

 Cambrian-Silurian series, or as pre-Cambrian lying nnconformably 

 beneath Ordovician sediments, the last being the interpretation 

 favoured by the Geological Survey as a, result of the investigatipns 

 now in progress, f This explanation has been applied also' to the 

 interpreitation of the Buller and Reef ton districts by Morgan 

 (1912), and Henderson (1917) respectively. 



While this possibility must not be overlcoked, namely that frag- 

 ments of a pre-Ordcvician gneissic platform may be present, there 

 must also be recalled a conception familiar to modern Scottish 

 geologists, and- advanced specially by Barrow (1893-1912) and 

 Harker (1917), namely, the presence of a central zone of most 

 deeply-seated metamorphism, which had been buried toi the greatest 

 depth in the orogeny, and had been invaded by plutonic rocks, 

 some gneissic, injected before the maximum of orogeny, some after 

 it showing little or no gneissic structure. J The regional meta- 

 morphism decreases away from a zone of greatest change, and here, 

 to, as also within the central zone of such a deeply altered rocks 

 series, there may be massive intrusions of a date much newer than 

 the gneissic rocks, and evirronnded by a metamorphic zone of 

 contact-rocks which are most marked where the regional meta- 

 morphism is least. § 



Commencing in the south-west of New Zealand : — Near the 

 coast of Preservation Inlet a band of graptolitic slates {aee later) 

 passing into phyllites, runs to the north-west. Tliey are invaded 

 to the north-east by pegmatitic granite, which also invades a mass 



* Professor Park adopts a similar view in a bulletin now in the press. (Private 

 communication). 



t Private communication from Mr. Morgan. 



t Henderson's suggested explanation (1017, p 10:5) of the formation of the gneissic and 

 massive plutonic rocks in the same eruptive epoch is rather different from this. 



, § We need not, in suggesting this explanation, accept Barrow's contention that such 

 conditions presuppose a pre-Cambrian age for the sediments and gneisses. 



