GEOLOGY OF THE LUZERNE QUADRANGLE 37 



and their total lack of metamorphism, they must be much younger 

 than the other Precambrian rocks of the quadrangle. Since Gush- 

 ing has shown these Adirondack diabase dikes to be older than late 

 Cambrian, they are, therefore, quite certainly of late Precambrian 

 age. These dikes of the quadrangle vary from fine to medium 

 grained, and they usually have a more or less well-defined ophitic 

 texture. In all cases where the determination could be made the 

 dikes show a strike ranging from north-south through northeast to 

 east-west, most of the strikes varying between north lO degrees 

 east and north 40 degrees east. Some of the dikes will now be 

 specifically referred to. 



The eastern one of the two dikes one-half of a mile north of 

 Hunt lake is fully 30 feet wide. It is clearly traceable for one- 

 eighth of a mile with a strike north 20 degrees east. The western 

 one of these two shows but a single good exposure. 



A fine-grained diabase dike 6 feet wide sharply cuts the large 

 pegmatite dike vertically in the feldspar mine i^ miles southwest 

 of Linwood school. A thin section of this diabase consists of basic 

 plagioclase and chlorite with much dark glass filling in between the 

 two. A very little pyrite was also noted. The section shows an 

 excellent ophitic texture. 



The diabase dike nearly 2 miles west of Conklingville is 45 feet 

 wide and traceable 200 feet. It cuts granite of the mixed rock area 

 almost vertically and parallel to the foliation. It strikes north 40 

 degrees east. 



Three-fourths of a mile northwest of Gailey hill several dikes 

 (the largest 8 feet wide) with east-west strike cut the coarse- 

 grained granite vertically about parallel to the foliation. These 

 dikes are traceable only a few rods. A thin section contains : 

 plagioclase (andesine to labradorite), 38; hornblende, 30; enstatite, 

 22; garnet, 5; magnetite, 4; and pyrite, i. The texture is fine 

 grained and rather uniform. 



At the eastern edge of the gabbro area 2 miles southwest of 

 Stony Creek station a diabase dike fully 10 feet wide with strike 

 north 30 degrees east cuts the gabbro, but both of these rocks are 

 there badly crushed due to faulting (see map). 



A diabase dike 15 feet wide with strike north 40 degrees east is 

 also badly crushed along a fault 23^ miles north of Stony Creek 

 village. 



A small dike by the road at the southeastern edge of Warrens- 

 burg village shows in thin section : labradorite, 61 ; augite, 22 ; 

 chlorite, 10; and magnetite, 7. 



