THE BARITE DEPOSITS OF MISSOURI 9l 



If the mineralizing solutions came from below, they must 

 have had some way of reaching the formations. The barite is 

 practically restricted to the upper part of the Potosi dolomite and 

 to the lower part of the Proctor formation. 



Evidence that the Potosi dolomite was uplifted, faulted, and 

 eroded before the deposition of the Proctor dolomite (and Emi- 

 nence), and that at the close of the Proctor there was another 

 period of erosion has been given above. These intervals during 

 which the region was land favored the development of the solu- 

 tion cavities found in these formations. 



The faults are believed to have furnished the channels along 

 which the mineralizing solutions rose, and since they were con- 

 fined to the Potosi formation, the solutions were unable to rise 

 further because of the overyling impermeable Proctor forma- 

 tion, and were thus forced to spread out along the contact of the 

 two formations. Here they availed themselves of the open spaces 

 afforded by the drusy quartz masses and the other openings in 

 the dolomite as well as the larger solution cavities. The latter 

 furnished channels along which they might pass to reach the 

 smaller fissures and openings, as well as a place for deposition. 

 The major deposition occurred in the Potosi formation since it 

 contains many more open spaces of all kinds. The veins were 

 formed by replacement or filling of the fault planes and other 

 fissures. 



That the deposition of the barite occurred before the last 

 period of faulting is proved by the fact that the Elvins, where 

 it is in fault contact with the Potosi dolomite, contains no barite. 

 Deposits of barite are found in the Potosi dolomite within a few 

 hundred feet of the fault, but no deposits are known to occur in 

 the Elvins formation. 



Source of the solutions 



It is believed that the solutions which deposited the barite 

 and associated minerals were derived from a deep source, pre- 

 sumably igneous rock. If such were the case, the solutions were 

 hot and contained in addition to the various metals, carbon 

 dixoide, sulfate radical, hydrogen sulfide, and possibly chlorides. 

 The only minerals present which are of any diagnostic value are 



