496 ." ■" KEW YORK STATE MUSEUM - ■ 



only two; the anorthoslte and gabbro, were recognized as intrusives 

 in the preliminary report on the region. The granite and syenite 

 together constituted a '' doubtful " area which was, for convenience, 

 called '' Series 1," the presumption being that they were older than 

 the limestone and possibly tO' be correlated with the Ottawa gneiss 

 of Canada. 



Granite. The granite of the Paradox Lake quadrangle is usually 

 gneissic. . 



It is believed to be igneous because of its constant composition 

 over wide areas ; it is regarded as intrusive into and younger than 

 the sedimentary hornblende gneiss because of the small dikes and 

 pegmatites which appear to radiate from the granite, cutting the 

 sedimentary gneiss. 



In no case could a true intrusive contact be found. In most 

 localities where the two gneisses come together, or where the massive 

 granite gneiss is in contact with the limestone, faulting is found to 

 be the cause. Where there is no fault in evidence, the contact is 

 obscured by swamps. 



In mineralogy this granite-gneiss is very constant. It contains 

 hornblende, orthoclase, plagioclase and quartz, with occasional acces- 

 sory biotite, muscovite, magnetite, pyroxene, apatite and zircon. 

 Some slides of this rock present the normal appearance of a horn- 

 blende granite, but usually the minerals are drawn out into gneissic 

 bands, the orthoclase changed to microcline ; the quartz showing 

 undulatory extinction ; the hornblende bent and twisted but unaltered 

 optically. Tiny shear zones are common, filled with secondary 

 quartz, chlorite or zeolites. Secondary garnets are occasionally 

 present, but are not so common as in the more basic rocks. Inter- 

 growths of quartz and orthoclase (micro-perthite) are common. 



Another variety is porphyritic, with phenocrysts of orthoclase. 



Still another variety is that which contains the Hammondville 

 ores. This type is conspicuous in the absence of ferro-magnesian 

 minerals, consisting mainly of quartz, microperthite and plagioclase. 

 A scattering of magnetite grains with very rare hornblende are 

 present as slight accessories. The hornblende is usually brown. 

 Occasionally the green variety is found. 



