HOT WATER SUPPLY OF THE HOT SPRINGS 441 



JUVENILE VS. METEORIC WATER 



One of the great triumphs of modern geology has been to estab- 

 lish that the majority of metalliferous ore bodies, including most 

 quartz veins, are deposited by ascending aqueous solutions which 

 are derived from and excluded from crystallizing igneous bodies. 



Granite rocks have been traced into pegmatite veins; pegma- 

 tite veins into metalliferous quartz veins; metalliferous quartz 

 veins into quartz veins without impurities. It has thus been 

 shown that aqueous vapors and gases gradually cooling and purging 

 themselves of many substances rise through the crust and approach 

 the surface in a purer and purer state. There is no theoretical 

 objection to cold water with a minimum of mineral matter being 

 attributed to a juvenile origin from an underlying crystallizing 

 igneous mass, except the difficulty of proof. The majority of 

 geologists do not hestitate to ascribe ore deposits to deposition from 

 juvenile water, yet they hesitate to ascribe a juvenile origin to 

 water emerging at the surface. It is well then to examine the 

 criteria on which a discrimination between these two classes of 

 water can be based. 



Springs of small volume, and large variation in flow and temper- 

 ature, can usually be referred to a meteoric origin. There are, 

 however, many difficulties in determining the precise geological 

 structure which gives rise to a particular spring. The requisite 

 structures necessary for such a spring are: (i) an intake area, 

 (2) a reservoir, and (3) a conduit to the surface. Under different 

 geologic conditions the three requisites assume a multitude of forms 

 and vary in size according to the hydraulic conditions. In a previ- 

 ous publication^ twenty-four named varieties, divided into five 

 groups, are described and illustrated. The field geologist, know- 

 ing the many possible structures, may have difficulty in deciding 

 on the right one for any particular spring because of lack of evidence. 

 Deep weathering of the rocks and a mat of vegetation and vegetable 

 mold are usual at springs and tend to destroy, locally at least, the 



' Kirk Bryan, "Classification of Springs," Jour, of GeoL, Vol. XXVII (1919), 

 pp. 521-61, 26 figs. 



