ALMANDITE AND ITS SIGNIFICANCE IN THE 



CONTACT ZONES OF THE GRENVILLE 



LIMESTONE^ 



GEORGE W. BAIN 

 Columbia University 



INTRODUCTION 



The highly metamorphosed rocks of the Grenville series have 

 attracted intense interest ever since Sir WilKam Logan gave them a 

 name and a place in geological literature. In view of the great wealth 

 of geological information obtained from these old crystallines it 

 would seem that they have nothing new to give to the science of 

 geology and mineralogy, yet every time they are studied they yield 

 some piece of information. The present article deals with one 

 mineral, almandite, its origin, alteration, and instability. These 

 changes are involved in the intense contact action produced by the 

 great Laurentian Batholith. 



LOCATION 



The area which was studied previous to preparing this paper 

 lies in Chatham Township, four miles northwest of the town of 

 Lachute on the North Shore branch of the Canadian Pacific Railway 

 44 miles west of Montreal. The district is on the very edge of the 

 Laurentian Highlands and the swift streams have cut moderately 

 deep valleys for a short distance back from the broad fertile plain 

 of the Ottawa Valley (Fig. i). 



GENERAL GEOLOGY 



The rocks of Chatham Township are chiefly old crystalHnes, 

 in part intensely metamorphosed sediments of early Precambrian 



^ The chemical and petrographical studies undertaken previous to preparing this 

 paper were carried out at Columbia Universitj' under the guidance of Prof. J. F. Kemp, 

 Dr. C. P. Berkey, and Mr. R. J. Colony to whom the writer is greatly indebted for 

 assistance, advice, and helpful criticism. 



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