332 BROWN & HERON: GEOLOGY AND ORE DEPOSITS OF TAVOY. 



He is of the opinion that the ore minerals were brought up in solution 

 by surface water which gained access to the molten magma through 

 fractures caused by the upheaval of the granite itself. His import- 

 ant paper is difficult to summarize and the interested reader is advised 

 to consult the original. Dr. Campbell can see " no evidence whatever 

 of pneumatolytic origin but much evidence of aqueous origin." He 

 reminds us of the existence of the soluble silicotungstic acid, Si0 2 , 

 4H 2 0, 12 WO 3 , and that the alkaline silicotungstates are readily 

 soluble in water. He states, " I believe that highly siliceous water 

 under high pressure and at moderate temperatures is capable of 

 carrying both tungsten and tin in solution, that this is the agent 

 which extracts them from the granite magma and transports them 

 to veins and that they do not pass upward in gaseous form." 



Regarding the opinion of Dr. Jones that wolfram is a lower 

 temperature mineral than cassiterite, Dr. Campbell states, « I 

 have examined very carefully the mixed wolfram-cassiterite ores 

 from most of the mines in the district and in the vast majority of cases 

 there is no shadow of doubt that wolfram was deposited before 



tin I have seen many hundreds of samples of cassiterite 



filling the spaces between wolfram crystals, enclosing wolfram 

 and carrying the impressions of its striations, several where it has 

 filled cracks in wolfram and two excellent examples of tin-ore crys- 

 tals actually formed on surfaces of wolfram." 



The same author has developed his views at greater length in a 

 more recent paper. 1 This may be divided into two parts, the first, a 

 general one dealing with the vertical range of meteoric water in the 

 earth's crust, the genesis of rock magmas discussed with reference 

 to W. H. Goodchild's recent work, and magmatic differentiation ; 

 the second portion may be said to apply the theories of the first 

 part in explaining the formation of the mineralized granite and 

 the ore-bearing veins of the Tavoy district, and to the general 

 question of the permanence of wolfram deposits in depth. 



The existence of a highly acid mother liquor, which may contain 

 all the constituents of granite or little else but silica and water 

 in which the tin and tungsten minerals are contained, because they 

 are more soluble in the acid differentiates than in the more basic 

 portion, and which deposits either pegmatite or quartz on cooling, 

 is postulated. Further, there is said to be abundant evidence in 



1 J Morrow Campbell (10). 



