" BATHOLITHS" OF HALIBURTON-BANCROFT AREA 785 



The granite was intruded between the layers of limestone. As 

 in the present case, long narrow layers of limestone are often 

 found isolated in the gneiss. These layers are in parallel bands 

 and the strike of their stratification conforms to the strike of the 

 gneissic structure of the surrounding granite. 



If the boundary between gneiss and pure limestone is sought, 

 it will invariably be found that there is a transitional contact zone. 

 The distinction between areas which may be designated as " Gneiss 

 with amphibolitic inclusions" or "Amphibolite" or "Limestone 

 invaded by much gneiss" depends upon the degree to which the 

 granite has invaded the limestone and altered it to amphibolite. 

 In general, on crossing the strike from limestone to amphibolite, 

 there is a gradual transformation of one rock into the other. The 

 amphibolite in turn is transitional to red gneiss through the inter- 

 mediate stage of gray gneiss. Xenoliths of amphibolite within 

 the gneiss are in no degree so abundant as stringers of amphibolite 

 varying from a few centimeters to a meter in diameter and the 

 schistose structure of which conforms to the gneissic structure of 

 the granite and the stratification of the limestone. 



Adams 1 attributes the parallel arrangement of these bodies to 

 movements of the granite after intrusion. He conceives that the 

 limestone blocks, stoped from the roof of the batholith, were 

 softened by heat and pulled out into lenses by no wage. 



The parallel banding of pre-Cambrian rocks is not a local fea- 

 ture, illustrated only in the rocks of the Haliburton-Bancroft area. 

 It is, rather, characteristic of most pre-Cambrian terranes. The 

 interbanding of gneiss of igneous origin with sediments is shown 

 by Lawson in his study of the Lake of the Woods. Hogbom 2 has 

 described similar relationships which are shown by the rocks about 

 Upsala, Sweden. 



The gneiss of the pre-Cambrian of the Adirondacks is so mingled 

 with limestone and other sediments that for years it has been a 

 mooted question whether to consider it of igneous or sedimentary 

 origin. It forms lenses and sheets in the sediments, or traverses 

 them so irregularly that an exact interpretation is difficult. 



1 Can. Geol. Surv., Memoir No. 6 (191°), 73~7%- 



2 Bull. Geol. Instu., Univ. Upsala, X (1910-11), 39. 



