VOLUME XXX NUMBER 4 



THE 



JOURNAL OF GEOLOGY 



May-'June ig22 



ON CONTACT PHENOMENA BETWEEN GNEISS AND 

 LIMESTONE IN WESTERN MASSACHUSETTS 



PENTTI ESKOLA 

 Geophysical Laboratory, Carnegie Institution of Washington 



CONTENTS 

 Introduction 

 Becket Granite Gneiss 

 Limestone and Skarn 

 Banded Gneiss Near the Limestone and the Variation of Its Mineral 



Composition 

 The Fe : Mg Proportion in the Various Bands of the Gneiss and in Its 



Different Mafic Minerals 

 Variation of Mineral Paragenesis in Metamorphic Limestone 

 Assimilation of Limestone by Granitic and Pegmatitic Magmas 

 Summary 



INTRODUCTION 



The eastern part of Berkshire County in western Massachusetts 

 is underlain by a vast area of granitic gneiss, known as the Becket 

 granite gneiss} 



' B. K. Emerson, "Geology of Massachusetts and Rhode Island," U.S. Geol. 

 Siirv., Bull. 5P7 (19 17). 



In older papers by the same author, "Geology of Old Hampshire County, Mass.," 

 U.S. Geol. Surv., Mon. 2g (1898), and "The Geology of Eastern Berkshire County, 

 Mass.," U.S. Geol. Surv., Bull, ijg (1899), this granite gneiss is designated in part as 

 "Becket conglomerate gneiss" and in part as "Tyringham gneiss." 



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