104 Transactions. 



receive more general support than the extreme views of Posepny 

 and Sandberger. 



According to the definition of lateral secretion by the latter, 

 the descending waters became charged with mineral matter by 

 leaching the rocks in the region of vadose circulation. On the 

 other hand, Posepny assumed that the ascending waters became 

 charged at great depths by coming in contact with a deep- 

 seated repository of metalliferous matter, the existenge of which 

 is necessarily hypothetical. 



The modification suggested by Becker leans towards the 

 ascension theory, and differs only from lateral secretion in 

 assuming a deeper source for the mineral contents of the vein- 

 matter. 



Summary. 



From the data recorded in the preceding papers we may 

 deduce the following conclusions respecting the genesis of ore- 

 deposits : — 



(1.) That the majority of ore-deposits are genetically con- 

 nected with igneous rocks. 



(2.) That circulating underground water and gases are the 

 principal agents concerned in the dissolution, primary 

 concentration, and deposition of vein-matter. 



(3.) That ore-deposits do not necessarily occupy pre-existing 

 fissures and cavities. 



(4.) That ore-deposits were in many cases formed by meta- 

 somatic replacement. 



(5.) That vein-filling waters are ascending waters, in most 

 cases probably of magmatic origin. 



(6.) That the mineral contents are derived from rocks con- 

 tiguous to the zone of fracture or zone of meta- 

 morphism. 



(7.) That the principal agents of dissolution are water and 

 gases aided by heat and pressure. 



(8.) That precipitation from the ascending waters takes place 

 in orderly horizontal zones in accordance with the 

 natural laws governing solution and precipitation. 



(9.) That secondary enrichment is in the majority of cases 

 due to the migration of mineral contents from a 

 higher to a lower level, through the agency of descend- 

 ing meteoric waters. 



The theories of lateral secretion and ascension of solutions 

 are based on the fundamental assumption that the mineral 

 matter filling cavities was deposited from circulating waters. 

 Their differences lie principally in the different conceptions as 

 to the direction and operation of the circulating liquids. 



