ACADEMY OF SCENCES] AMERICA. 61 



recall in some degree those of the southwestern portion of New Zealand. In the southern end of 

 Vancouver Island (Clapp '12, '13, '14, '17) shows that an extensive series of Lower Mesozoic 

 andesite and basaltic lavas were invaded during the Jurassic folding by gabbro-diorite-gneiss, 

 diorite, and granodiorite, with a series of later dykes. Resting on an eroded surface cut from 

 these are a series of Cretaceous conglomerates and sandstones, followed by very much altered 

 (usually albitised) pillow-lavas, agglomerates, and cherty tuffs, which were strongly folded and 

 invaded by gabbro which passes upward through a transitional zone, 1 to 3 feet in width, into 

 granite. In one area described by Cooke ('19) an oval mass of greatly varied, and peripherally 

 gneissic, olivine-gabbro has a marginal zone of augite-gabbro, and these pass up into small 

 masses of granite and anorthosite, the several rock-types being sharply separated or linked 

 by transitional zones, usually a few inches in width. The intrusion of gabbroid and granite 

 dykes and the production of hornblendite and aplite were the last events in the consolidation 

 of this mass. Camsell ('13) has described a further development in the Tulameen area of 

 British Columbia. Here intrusive into Mesozoic argillites and limestones, with intercalated 

 basic effusive and clastic rocks of submarine origin, there is a roughly lenticular mass of 

 pyroxenite and peridotite 7 miles long and 2 miles wide; the central portion is dunite, the 

 envelope pyroxenite. Segregation-veins of biotite-olivine rock occur in the dunite, and 

 hornblendic pegmatites in the pyroxenite. The margin of the intrusion conforms to the 

 strike of the invaded rock, into which several sheets of the pyroxenite have been thrust. 

 Locally " augite-syenite " with a gabbroid facies has been injected, followed by granodiorite, 

 whde Cretaceous rocks lie upon an eroded surface of the granodiorite. Evidently the com- 

 plex may be grouped with the series of intrusions which accompanied the main Rocky 

 Mountain folding at the close of Jurassic times. The special point of interest in regard to this 

 mass of peridotite is the occurrence in it of some diamonds. This has led Camsell to correlate 

 it with the peridotite of Pike County, Arkansas, but the correlation is not justifiable on tectonic 

 or petrographic grounds. The intrusion of the Arkansas peridotite was not accompanied by 

 noteworthy folding, and it contains meldite and perofskite and much greater amounts of lime, 

 alkalies, and titanium, and a lower percentage of magnesia (25 per cent) than are normal for 

 peridotites or occur in the Tulameen peridotite, of which the composition is quite a normal one 

 for a peridotite and contains 40 per cent of magnesia. Compare with this the occurrence of 

 diamonds in normal peridotite in Tasmania (p. 37). 



Daly's ('12) study of the Cordillera along the forty-ninth parallel shows an extremely 

 complex series of igneous events. Commencing on the east, in the Purcell Mountains, the 

 sandstones forming during pre-Cambrian times were interbedded with basaltic lavas and a 

 little rhyolite and invaded by a series of composite sdls composed of gabbro, generally forming 

 the whole or the lower portion of the sill and granophyre forming the upper, and in one occasion 

 the middle portion of the sill, while a rock of intermediate composition separates the two types 

 of rock. Daly considers these result from gravitational differentiation of a magma acidified by 

 absorption of the overlying siliceous sediment, but Schofield ('14) gives weighty criticisms of 

 this view and concludes they arose as intrusions from an intercrustal reservoir containing a 

 differentiated magma. Comparison should be made with the composite sills described by 

 Harker ('04) in Skye. The Rossland volcanic series consists of an older and possibly Carbon- 

 iferous series of basaltic and andesitic lavas and tuffs, now partly schistose. Newer than these, 

 but difficult to separate from them, are further basalts, andesites, and latites, invaded by a 

 monzonite which merges locally into a hornblende-peridotite. This was injected probably 

 during the Jurassic orogeny. Gabbros, with peridotitic facies, occur in the same region, and a 

 porphyrinic harzbergite or picrite occurs (possibly as a sill) in the volcanic rocks, which are 

 intersected by a dike of dunite. In the Columbia Mountains highly metamorphosed basic 

 volcanic rocks of Paleozoic or Mesozoic age have been invaded by small masses of serpentine. 

 In the Okanagan Mountains a long series of plutonic intrusions occur. Upper Paleozoic and 

 possibly Triassic sediments and basic volcanic rocks were invaded, perhaps at the close of this 

 period, by gabbro and peridotite. During the intense deformation in Jurassic times grano- 



