THE GOWGANDA LAKE DISTRICT, ONTARIO 671 



examining the association of albite-rich igneous rocks described in 

 the literature. 



In California^ the soda-syenite famous for its association with the 

 Mother Lode gold deposits occurs along the contact of basic igneous 

 rocks with Mariposa slates. This syenite is in places an almost pure 

 albite rock; at others it contains some quartz and muscovite. 



In Alaska the Treadwell soda syenite^ of the Treadwell mine cuts 

 slate and is followed by gabbro. 



In Ireland, at Croghan Kinshela, albite granite here associated 

 with normal potash granite cuts Silurian slates.^ 



In the Isle of Man albite-rich dikes associated with diabase cut 

 Silurian slates.^ 



The albite-rich keratophyres of Westphalia cut slates. ^ 



Quartz keratophyres in Australia are associated with diorites and 

 cut slates.^ 



A notable point concerning all of these is their small quantitative 

 importance. 



If we extend our search to rocks rich in plagioclase near albite, we 

 find the same general association. 



In the Marysville district of Montana a rock made up of quartz 

 40 per cent, oligoclase-albite 40 per cent, magnetite 10 per cent, 

 muscovite 10 per cent, has been produced at the contact between 

 gabbro and altered argillaceous sediment by a process of "hydro- 

 thermal alteration along the contact plane."' 



Plumasite, an oligoclase-corundum rock, occurs in California as a 

 dike cutting peridotites which in turn cut clay slates.^ It has been 

 considered genetically related to the albite syenites. The excess of 

 alumina (corundum) in the plumasite is suggestive in relation to its 

 genesis by interaction of the basic magma and clay slates. 



1 H. W. Turner and F. L. Ransome, Folios 41, 45, and 63, U.S.G.S. 



2 G. F. Becker, i8th Ann. RepL, U.S.G.S., Part III (1896), 39 and 65; C. W. 

 Wright, Bull. 287, U.S.G.S., 95. 



3 S. Haughton, Q.J.G.S. (1856), 268; W. J. Sollas, Tr. R. Ir. Ac, XXIX (1891), 

 427. 



4 B. Hobson, Q.J.G.S. (1891), 432. s O. Mugge, L.J. (1893), ^.B. VIII, 535. 

 •5 A. Howitt, Geol. Survey Victoria, IV (1877), 75-117. 



7 Barrel, P.P. 57, U.S.G.S., 48. 



8 A. C. Lawson, Bull. Univ. 0} Cal., Ill, No. 8, p. 219. 



