266 Transactions. 



Tliis is well shown in the specimens from veins on the west side of the 

 bay, where the rock approaches a sagvandite (Rosenbusch's " Elemente 

 der Gesteinslehre," p. 549). Large quantities of carbonate are found in the 

 rocks containing much diallage, as well as in the normal harzburgite, 

 showing that the enstatite in other ultrabasic rocks passes into carbonate ; 

 unless, indeed, the process is a reverse one, and this marble is passing into 

 a magnesian silicate rock owing to the effect of an intrusive mass of dunite. 

 However, in some cases here the alteration enstatite to talc certainly occurs, 

 as crystals occasionally show a change in that direction. 



Besides the above, large boulders of rocks of somewhat abnormal type 

 were found. They cannot have come from a distance, and they show con- 

 nections with the rocks found in position. They are distinctly foliated, 

 and contain a large amount of garnet. The first is a greenish-grey rock 

 with a tinge of pink, close-grained, showing faint schistose structure : it 

 is composed principally of reddish garnet, with augite, olivine, titanite, 

 and chromite, some quartz of secondary origin, and much carbonate (calcite 

 or dolomite) ; the garnet grains are in strings and aggregates, often in rudely 

 parallel arrangement, and show marked signs of crushing ; the whole struc- 

 ture is cataclastic. The second specimen is a green rock, with cleavage- 

 surfaces of green augite strongly showing : it is composed of greenish augite 

 occasionally showing diallage structure, grains of £)livine which are clear 

 and only occasionally passing into serpentine, occasional enstatite, and 

 much crushed garnet of slightly reddish tint in grains distributed irregularly 

 but sometimes collected in masses ; the structure is markedly cataclastic. 

 The first of these rocks is a eulysite or'garnet peridotite, in connection with 

 which it may be observed that Rosenbusch, in his work referred to pre- 

 viously, has noted the association of carbonates with rocks of this type. 

 The second rock contains much less garnet, and is more closely related 

 to the dunite. As it contains a considerable amount of monoclinic pyroxene 

 it should perhaps be called a garnet-wehrlite. Both of these rocks seem to 

 be m^odifications of the ultrabasic intrusions which have penetrated the 

 gneisses of this area, and belong to that great series of intrusions which 

 occur up the western side of the Southern Alps to Nelson and reappear 

 in New Caledonia. The date of the New Zealand intrusions was first of 

 all considered as Devonian, but the consensus of opinion at the present 

 would make them much younger, probably Upper Jurassic or Lower Cre- 

 taceous ; however, according to the reports of Messrs. Pelatan and Piroutet, 

 the serpentines and allied rocks of that island, which is so closely connected 

 geologically with New Zealand, are certainly post-Cretaceous, and there 

 is no reason wh)' the New Zealand rocks of like facies should not be of the 

 same date. An mference drawn from two widely separated localities is 

 certainly somewhat dangerous ; but the almost entire absence of fragments 

 of ultra-basic rocks in detrital deposits in this country is certainly sug- 

 gestive, although explanations of their absence can be readily put forward, 

 and of course they may be discovered after a further examination of the 

 deposits. The date of the intrusion of the New Zealand peridotites may 

 be as recent as Tertiary times and possibly late Tertiary times. 



In concluding, the author wishes to acknowledge the imperfect and 

 unsatisfactory character of these petrological notes ; they will serve, how- 

 ever, to mark the complex character of the area, and to emphasize Captain 

 Hutton's conclusion that the rocks are not truly Archsean, but metamor- 

 phosed igneous, with perhaps metamorphosed sedimentary rocks included 

 amonsf them. 



