450 Hawkins — Notes on the Geology of Rhode Island. 



actinolite schist along Sin and Flesh Brook, southeast of 

 Tiverton, are apparently of similar age. 



In the extreme northern part of the State, at Round 

 Top, a fissile, closely plicated muscovite schist is asso- 

 ciated with quartzite. The schist carries chlorite, and 

 also garnets of small size and rarely black tourmaline. 

 It is probably also closely related to the green schist 

 series, being mapped as part of the Westboro quartzite 

 by Emerson. 



The green schists are quite generally gabbroid in com- 

 position (see analyses, Table II), and in appearance and 

 behavior, though badly sheared, suggest "the derivation 

 of some part of the material from basic tuffs' ' (Emer- 

 son and Perry, op. cit.), the tuffs being interbedded with 

 the quartzites. Interlayering of the two kinds of rock at 

 the contacts also affords for these authors additional evi- 

 dence of sedimentary origin for the schist. There are 

 a few beds of the green schist in the quartzite, however, 

 which seem to actually represent intrusive sills in lit- 

 par-lit injection. One of these appears as a breccia of 

 quartzite fragments in green schist matrix at Violet Hill, 

 Manton (underneath the perched granite bowlder on the 

 hill just north of the Manton Avenue quarry) ; and thin, 

 ramifying, sill-like layers of schist in a quartzite at a 

 small exposure southeast of Oak Valley, in North Smith- 

 field. The appearance of large, isolated masses of 

 quartzite, too large and isolated to represent conglom- 

 eratic bowlders, seems also to point toward actual 

 intrusion. 



The schists in their coarser phases exhibit a mass of 

 long green actinolite blades intermingled sometimes with 

 areas of granular or saccharoidal feldspar. An extreme 

 case of the production of secondary feldspars of this kind 

 is in the rock exposed along the highway at "West Green- 

 ville, where it is filled with closely set pseudo-phenocrysts 

 of a saccharoidal feldspar near albite in composition, 

 lath-shaped, some attaining a size of 1 cm. X 3 cm., and 

 showing roughly parallel arrangement simulating flow 

 structure. About two miles north of this latter place 

 the green schist grades into a true gabbro. In contrast 

 to this, the gabbro at Woonsocket (Huntington Avenue) 

 contains inclusions of green schist surrounded by reac- 

 tion rims. 



