F. H. Lahee — Metam^orphism and Geological Structure. 461 



Immediately above the dikes depicted in figs. 10 and 12, the 

 stratification, which was perfectly clear in the junction of a 

 fine dark schist and a coarse light schist, had its dip and strike 

 about parallel to the average attitude of the schistosity. Care- 

 ful search was made for bedding where crumpling might 

 occur, but with little success. In only one instance there 

 were very obscure traces of close folding. Yet the very fact 

 that the cleavage is contorted proves that the pre-existing 

 stratification must also have suffered deformation of like 

 nature. 



The quartz vein phase : Description. — Large and small 

 veins of quartz are found throughout the southern half of the 

 Narragansett Basin. They are more abundant southward and 

 westward. 



The quartz of these veins is milky or creamy in color. 

 Feldspar has been found in small quantity, generally near the 

 margins of the veins, as far north as the Devil's- Foot Ledge 

 (in B : 9, where vertical dip is shown, fig. 1), near East Green- 

 wich, and, eastward, on Dutch and Conanicut islands. Locally, 

 a little chlorite, muscovite, sericite, pyrite, etc., have been dis- 

 covered. 



Miarolitic cavities are occasionally seen (East Providence 

 area and Sachuest Neck), and, in these, crystal terminations 

 may be well developed ; but, as a rule, the quartz is massive. 

 Comb-structure was not recorded. 



— Relations between the quartz vein phase and the pegmatite 

 phase. — We have explained above that pegmatite apophyses 

 may become wholly quartzose at their extremities. We now 

 see that the quartz veins may contain some feldspar. Every 

 gradation between typical pegmatite dikes and pure quartz 

 veins may be observed in this region. On the Bonnet, where 

 all the varieties are best illustrated, quartz veins sometimes cut 

 the pegmatite. Hence we infer that the quartz veins are 

 genetically allied to the pegmatites and represent the extreme 

 acid phase of the Acid Intrusive Series.* 



— Relations of the quartz vein phase to the Carboniferous 

 sediments. — Those veins which cut the Carboniferous sedi- 

 ments are of every variety of shape and size. Usually they are 



* The same relation between quartz veins and pegmatite dikes has been 

 recorded in other regions by I. H. Ogilvie (Geology of the Paradox Lake 

 Quadrangle, N. Y., N. Y. State Mus. Bull. 96, 1905), xx ; Van Hise (op. 

 cit., p. 724); T. T. Read (Nodular-Bearing Schists near Pearl, Col., Jour. 

 Geol., xi, p. 493, 1903) ; J. F. Kemp (The Role of the Igneous Rocks in the 

 Formation of Veins, Am. Inst. Min. Eng., Trans, xxxi, p. 169, 1902); 

 Crosby and Fuller (op. cit,, pp. 329, 334); G. H. Williams (General Rela- 

 tions of the Granitic Rocks in the Middle Atlantic Piedmont Plateau, U. S. 



G. S., Ann. Rept. xv, p. 657, 1894); C. R. Van Hise (Principles of North 

 American Pre-Cambrian Geology, U. S. G. S., Ann. Rept. xvi, Pt. I, p. 581, 

 1895, p. 688) ; and many others. 



