GEOLOGY OF THE REMSEN QUADRANGLE 



15 



in oligoclase and the dark colored minerals, it is nevertheless 

 thought to be a facies of the homogeneous syenite mass. The dif- 

 ference in mineralogical composition just noted might well be 

 explained on the basis of differences in conditions of cooling and 

 crystallization where the molten syenite was so thoroughly in- 

 volved with the Grenville and its associated igneous rocks. Con- 

 tact metamorphic effects must have been common and portions of 

 the Grenville may at times have been absorbed by the molten 

 syenite. 



Another common type ranges from gray and dark gray to al- 

 most black, the color depending upon the biotite mica content, which 

 is often very high. Other minerals which may be present are anor- 

 thoclase, oligoclase, quartz and smaller amounts of magnetite or 

 hornblende. Rocks of this type usually appear as dark bands 

 within the syenitic masses. 



Other rocks ranging from light to dark color and containing 

 garnets are thought to be Grenville, but they are so closely involved 

 with other masses that they can not be mapped. Such a light 

 colored feldspar rock with large garnets occurs along the railroad 

 about 2 miles northeast of Anos Siding. 



Another rock generally classed with the Grenville is rich in silli- 

 manite and sometimes occurs in the complex as for instance at 

 Forestport. 



A rock type rich in hornblende and black in color occurs in 

 distinct bands in the complex. A rock of this same character is 

 found in the Grenville and was considered to be an old metamor- 

 phosed gabbro. Besides hornblende the rock contains feldspar 

 ranging from oligoclase to labradorite and a little magnetite. 



Another rock often present in very irregular masses and ap- 

 parently cutting through all the others is a pegmatite. It is gen- 

 erally coarse grained and not in distinct veins. 



All sorts of gradations occur between the types here described 

 and these rocks in turn often grade into either the syenite or the 

 Grenville masses proper. 



Undetermined Precambric areas. Two areas have been indicated 

 upon the geologic map as Precambric but of unknown character, 

 because the rock masses are completely concealed from view by 

 heavy glacial drift deposits. The area between Forestport and 

 Enos is probably mostly made up of the Syenite-Grenville complex 

 because those rocks bound the area both on the north and on the 

 south. The area between West Canada creek and Little Black 

 creek probably is syenite on the west and Syenite-Grenville on the 

 east. 



