82 Transactions. 



examined under the microscope it was seen that the differences- 

 were due to unimportant variations in a diorite rock. The rock 

 is not coarse-grained, and the feldspar is nearly all triclinic, ande- 

 sine and oligoclase being chiefly present. All the ferro-magnesian 

 mineral is hornblende, but it is much decomposed into serpen- 

 tinous and chloritic substances. There is some magnetite. In 

 the absence of analyses, the rock appears to approach the syenites 

 somewhat closely. At Ahipara other specimens were obtained 

 that appear to represent the mass that extends from that locality 

 to Reef Point, though the actual specimens were obtained from 

 Ahipara only. The rock, again, is not particularly coarse-grained, 

 and in hand-specimens is less grey than the diorite mentioned 

 above. The separate minerals are clearly seen in hand-specimens, 

 and, in addition to feldspar and a dark ferro-magnesian mineral, 

 olivine was evidently present. 



When seen in thin sections the rock is at once identified 

 as an olivine norite. The feldspar is a basic variety of labra- 

 dorite. Augite is plentiful, and but slightly schillerised. The 

 hypersthene is not abundant, and is generally associated with 

 olivine, which is rather frequent. This appears to be the only 

 olivine norite recorded from New Zealand, though it is probable 

 that similar rocks exist in the Darran Mountains, near Milford 

 Sound. Other specimens of plutonic rocks were obtained from 

 the Raetea Saddle. They were almost entirely norites, but 

 were wanting in olivine. 



In those sections that were seen the relations between the 

 plutonic rocks and the Mesozoic shales were not clearly dis- 

 played. No actual contact was observed, but from the irregular 

 succession of the rocks on the road to the Raetea Saddle it was 

 evident either that the Mesozoic sediments rested on a highly 

 eroded surface of plutonic rock, or that the plutonic material 

 was intruded into the sediments, and is therefore of Post- Meso- 

 zoic age. This is the view taken by McKay, and, although 

 it is impossible to mention any section that negatives it, 

 there are a few facts which suggest that more vigorous investi- 

 gation is yet required. It is obvious that the intrusion of such 

 large masses of plutonic rock would be likely to induce much 

 contact action, yet when search was made in the. sediments no 

 evidence of contact action could be found, even when the out- 

 crop of norite was close at hand. The slight schillerisation of 

 the pyroxene also indicates that the plutonic matter has been 

 subject to much dynamic action since its formation. Since 

 there is no evidence of earth-movements in this district since 

 the period of folding of the Mesozoic sediments, it would appear 

 that the norite received its character of schillerisation at a 

 period not later than that of the folding of the Mesozoic 



