THE ORIGIN OF THE WOLFRAM AND CASSITERITE ORES 331 



W. R- Jones. — In a paper published in 1918, Dr. W. R. Jones 

 has developed his views. 1 He holds that the origin of the wolfram, 

 tin-ore, scheelite and associated minerals found in the Tavoy district, 

 is closely and definitely related to the fluxes and solvents which eman- 

 ated from the granite magma, and that there is little doubt that 

 such minerals as those already mentioned, together with molybdenite, 

 bismuth, bismuthinite, pyTite, mispickel and some others, common in 

 the lodes in Tavoy, were formed through the agency of magmatic 

 gases and solutions. The watery acid mother liquor, formed by 

 the differentiation of the magma, and rich in mineralizing gases and 

 solutions, followed immediately and often accompanied the in- 

 trusion of the very acid magma, and when they reached a tempera- 

 ture zone sufficiently cool, the minerals were deposited. The wolf- 

 ram and tin ore occur where the chilling was greatest and this is 

 given as the reason why the hanging and foot walls of veins carry 

 most values and why narrow veins have higher percentages than 

 wide veins. Greisens were formed by gases and solutions attacking 

 the rocks beyond the well-defined vein walls, and wolfram and cassi- 

 terite occurring in granite as primary minerals, are regarded as due 

 t ,o the escape of the mineralizing gases with the first main intrusion. 

 Dr. Jones attaches great importance to temperature as a factor 

 determining the zones of deposition of wolfram and tin-ore and 

 to the powerful fluxing action of the mineralizing gases and solutions, 

 which enabled the magma to crystallize at relatively low tempera- 

 tures, and hence to be introduced into narrow fissures now forming 

 quartz and pegmatite veins extending hundreds of yards into the 

 adjacent schists and phyllites. He believes that the evidence 

 in the Tavoy district is in favour of regarding sulphides as having 

 played a most important part as " carriers " of wolfram and tin-ore, 

 and finally, that wolfram in general appears to have been deposited 

 at lower temperatures than has tin-ore in the Tavoy district, a 

 theory that has a most important bearing on the future of the 

 mining industry, if it proves tenable. 



J. Morrow Campbell, 1918.*— Dr. Morrow Campbell rejects 

 both the magmatic and pneumatolytic theories of vein filling in 

 Tavoy, believing that the presence of wolfram disseminated as a 

 primary mineral throughout granite provides a refutation of both. 



1 W. R. Jones ( 15), pp. 33-44. 



2 J. Morrow Campbell (9). pp. 76-89. 



