130 PROCEEDINGS OF THE AMHERST MEETING 



GENETIC FEATURES OF ALNOITIG ROCKS FROM ISLE C ADIEU X. QUEBEC 



BY N. L. BOWEN 



(Abstract) 



Aluoitic rocks at Isle Cadieux, near Montreal, Canada, are found to consist 

 principally of monticellite alnoite. Besides this type, there is a variety con- 

 sisting almost exclusively of melilite and biotite. 



A study of the relations of the minerals indicates that the rock originally 

 consisted of augite and chrysolite and was nearly completely consolidated as 

 such. These minerals were then attacked, with lowering temperature, prob- 

 ably by their own interstitial liquid, as it changed in composition, and they 

 were replaced by monticellite, melilite, and hiotite with marialite, perovskite, 

 and titaniferous magnetite as minor products of the reaction. The monticel- 

 lite is itself replaced by melilite and biotite, and the melilite-hiotite rock is 

 the end product of the replacement. 



The replacement was accomplished by an alkalic liquid (magma), which 

 formed monticellite from augite by desilicating it, and later gave rise to 

 melilite and the more definitely alkalic mineral biotite. 



In an experimental part of the paper equilibrium in mixtures of nephelite 

 and diopside is determined. It is found that from intermediate mixtures 

 forsterite and melilite are the first products to crystallize, and the melilites so 

 formed are analogous to natural melilites in composition and optical properties. 



It is thus proved experimentally that nephelite reacts with diopside to form 

 melilite, a reaction analogous to that which is considered to have taken place 

 between augite and alkalic liquid in the natural rocks. This reaction is of the 

 nature of a desilication of the pyroxene. The natural liquid, as modified by 

 the reaction, passed on and possibly gave rise to analcite dikes. 



Presented extemporaneously. 



8ILLIMANITE-SCHIST INCLUSIONS IN GRANITE* 



BY WILLIAM J. MILLEK 



(Abstract) 



While engaged in geological field-work in central Saint Lawrence County, 

 New York, under the auspices of the New York State Museum, during the 

 summer of 1019, the writer found two areas showing a rather remarkable 

 combination of Precarnbrian rocks. Both areas are within the Russell Quad- 

 rangle. The smaller one, near the middle of the quadrangle, is about 1% 

 miles long, with a maximum width of one-fourth of a mile. This will be re- 

 ferred to as the northern area. The other area, in the south-central part of 

 the quadrangle, is fully 4% miles long, with a maximum width of three-fourths 

 of a mile. This will be referred to as the southern area. There are many 

 fine exposures in both areas. The main bulk of the rock of each area is 

 medium-grained, pink, moderately foliated granite, consisting chiefly of micro- 

 dine and quartz in nearly equal amounts, together with from 1 to .'5 per cent 

 of magnetite and usually less than 1 per cent each of biotite, muscovite. and 

 zircon. 



1 Published by permission of 1he New York St;ile Geologist. 



