REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 r47 



RELATION OF AUGITE3 SYENITE TO GNEISS 



Thougli the observations eo far recorded would seem decisive 

 a:s to the time relations between these two rocks, the contacts of 

 the Tupper lake augite syenite in other directions are with gneiss- 

 es, into which they grade and fade out, as if they represented 

 portions of the same great complex, and these are the usual phe- 

 nomena in the Adirondack region, the augite syenite seldom, if 

 ever, showing sharp boundaries against any rocks, with the single 

 exception of the Grenville limestones and associated echists and 

 gneisses. The presentation of a few detailed observations will 

 be helpful as a prelude to the discussion of the phenomena. 



Section from Tupper Lake Junction to Horseshoe 



Nearly a mile below the depot at Tupper Lake a cut in a mas- 

 sive rock ridge (898) shows a coarsely gneisBoid rock, approach- 

 ing granite in composition, in which are occasional amphibolite 

 streaks which- may represent either drawn oult inclusions or 

 segregations. Along with the red rock, and grading into it, is 

 much green rock v^hich closely resembles the red except for 

 color. The green rock can not be distinguished from ordinary 

 augite syenite of the acid type^ consisitimg mainly of feldspar, but 

 with some 15^ to 2Qfc of quartz and some 10^ of bronzite, horn- 

 blende and augite, named in order of abundance, and the usual 

 zircon, titanite, apatite and magnetite in small quantity. Except 

 for a little oligoclase the feldspar is all alkali feldspar, inter- 

 growths of orthoclase and albite with the micrographic form 

 more prominent than the microperthitic. The red rock is more 

 quartzose and the pyroxenes have disappeared, but it appears to 

 grade into the other and represent its granitic phase. Precisely 

 similar admixtures are found in Litchfield park and elsewhere 

 near the syenite periphery. 



Beyond this point the railway soon crosses the Raquette river 

 and then turns westward along it, no further outcrops appearing 

 for more than a mile. At 2^ miles from the depot is a cut in a 

 greenish gray rock (1000), mainly very fine grained and gneissoid 

 but having also coarse bands, which does not appear like the 



