474 A. F. BUDDINGTON 



About six miles south of Manuels, lying between a series of green 

 slates and the Holyrood granite, a more or less elliptical-shaped mass 

 of gabbro forms a conspicuous ridge in the topography. This 

 gabbro has a tendency toward a gneissic structure but without any 

 particular evidences of dynamic metamorphism. It is quite inti- 

 mately penetrated by ramifying apophyses of granite and by epidote 

 veins, which are especially common along the joint planes. In thin 

 section the rock is seen to be hypautomorphic granular to ophitic 

 in texture and to consist essentially of light-green hornblende and 

 labradorite. The feldspars are extensively altered to sericite, and 

 some of the hornblende to intergrown fibers and blades of epidote, 

 zoisite, and quartz. Many of the hornblendes are twinned parallel 

 to the orthopinacoid, and by an occasional resemblance of crystal 

 form give indications of an apparently primary origin. Whether 

 this rock is the result of recrystallization during the intrusion of the 

 granite or whether it is primary is difficult to say. A chemical 

 analysis is given on page 476, No. i. In this connection it may be 

 well to note that where the road crosses Seal Cove Brook there is 

 an outcrop of hornblende porphyrite with phenocrysts of hornblende 

 up to 10 mm. in length and plagioclases averaging 2-3 mm. in 

 length. In thin section this rock is found to consist of idiomorphic 

 phenocrysts of labradorite and hornblende in a groundmass in some 

 places consisting of a microcrystalline, elsewhere of an almost 

 crypto-crystalline, aggregate of plagioclase microHtes, quartz, 

 and an altered ferromagnesian mineral in sparse amount. The 

 plagioclases show a zonary banding. 



To the west and south of Woodfords is a stock of granodiorite 

 about two miles long and one-half mile wide, intrusive into the beds 

 of the Avondale volcanic series. Dikes from this mass are excep- 

 tionally rare, but enough evidence was found to prove its intrusive 

 nature. The rock is light colored and medium grained, consisting 

 of pink orthoclase, black hornblende, and quartz. The latter is 

 abundant in small grains which show upon a fresh surface only when 

 closely examined. On the weathered surface, however, they stand 

 out in rehef and give to the rock the appearance of a typical granite. 

 With the microscope the rock is found to consist of andesine, ortho- 

 clase, augite, and quartz, with abundant rods and grains of apatite. 



