780 THE TIN-DEPOSITS OF NEW ENGLAND, N.S.W., I., 



There are three geological units within the tin-field — (1) a 

 series of slates and claystones; (2) a series of granites; (3) a series 

 of basalts; while a fourth flanks its eastern side. The slates are 

 Palaeozoic, and are probably of Silurian age. The basalts are the 

 youngest of the formations, and their age has been determined 

 as Tertiary. The granites are intrusive into the Palaeozoic slates, 

 and their age has been provisionally stated as Permian. 



There are two chief granite-types — (1) the "Acid Granite " of 

 Mr. E. C. Andrews, and (2) an older and more basic rock which 

 I have called the Tingha Granite. 



The "Acid Granite" is chiefly a quartz-felspar rock. A little 

 biotite is present in some phases; and in another phase tourma- 

 line is fairly abundant. The Tingha Granite also has several 

 phases, those at Oakey Creek and south of Tingha being the 

 most important. The tin-ore deposits have been found always 

 closely associated with the "Acid Granite," though post-dating 

 the solidification of that rock. It is very common to find the 

 ore-deposits close to the contact of this rock with the older Tingha 

 Granite and the slates. AVhere the ore-deposits occur at a dis- 

 tance from such contacts, there is usually evidence to show that 

 there has really been a contact at no great vertical distance, and 

 that this has been removed by denudation. 



On examining the fracture-systems of Elsmore, Emmaville, 

 and Tingha, it was concluded that the force causing these was a 

 thrust from the east, or a torsional stress having the axis of 

 torsion approximately east and west. It was noted that the 

 system of fractures corresponds closely with the general trend of 

 the tin-bearing belt, both being best developed in a direction 

 about N.E. by E. 



The tin ore-deposits have been grouped into a number of classes. 

 The chief of these are (a) the quartz-quartzose type; (6) the 

 quartz-felspar type; (c) the pipes; and {d) the chlorite-deposits. 



In conclusion, I should like to record here my indebtedness to 

 the following gentlemen : to my brother, Mr. C. M. Cotton, who 

 accompanied me during the greater part of the field-work, and 

 rendered much assistance by his observations and suggestions; to 



