ORIGIN OF CARBON-DIOXIDE INCLUSIONS. 667 



gone to the extreme recognized by observation, muscovite and biotite may be 

 destroyed, with the production of such heavy anhydrous minerals as garnet, 

 staurolite, etc. Therefore the water apparently does not make its way 

 downward, or if it does it is water occluded between the solid molecules 

 rather than water combined with them; but as already stated, there is no 

 evidence that water can exist in important quantity in such positions. From 

 the above facts, since the amount of water apparently decreases with the 

 intensity of the metamorphism, or practically, disregarding local irregulari- 

 ties, with depth, and the freed water must escape somewhere, I conclude 

 that the probable general movement of the water present or produced by 

 dehydration and from magmas in the zone of anamorphism is upward into 

 the belt of cementation. 



This conclusion is confirmed by other facts in connection with meta- 

 morphism. It has been said, and will be fully explained, that silication of 

 carbonates, forming silicates and releasing carbon dioxide, is one of the 

 chief reactions of the zone of anamorphism." In the rocks metamorphosed 

 under deep-seated conditions inclusions of liquid and gaseous carbon 

 dioxide in the cavities are very common. When formed all of the occluded 

 carbon dioxide was probably a dense gas, because above its critical tem- 

 perature. Under surface conditions, below critical temperature and with 

 the high pressures of the gaseous portions, the carbon dioxide largely 

 condenses to a liquid. It is a fact that waters rising from a deep-seated 

 source almost invariably carry large quantities of carbon dioxide. It seems 

 highly probable that much of the carbon dioxide brought up by the rising 

 deep-seated waters is a portion of that carbon dioxide liberated by the 

 process of silication of the carbonates. If this be true, it is further probable 

 that the upward movement of the carbon dioxide was accompanied by 

 water or water gas, for there is no reason why one should go up and the 

 other down. 



Therefore it seems to me that the principles of physics and the facts 

 of observation both lead to the conclusion that, so far as the vertical 

 circulation of water between the zone of anamorphism and the belt of 

 cementation are concerned, the transfer is upward, from the former to 

 the latter. 



°See Le Conte, Joseph, Genesis of metalliferous veins: Am. Jour Sci., 3d ser., vol. 26, 1883, p. 9. 



