Park. — Origin of Metal-bearing Sohitions. 101 



is not in accord with the hydro-fusion theory of modern petrolo- 

 gists._ 



Rickard, who possesses a personal knowledge of the goldfields 

 of Australia and New Zealand, discusses the probable origin of 

 the veins of the Thames Goldfield, in the latter country, and in 

 the main agrees with Captain Hutton that they were formed by 

 processes of lateral secretion by thermal waters. 



Professor J. Le Conte* in a carefully prepared thesis combats 

 the extreme views of both Posepny and Sandberger. He makes 

 an earnest attempt to combine what is true in each, and reconcile 

 their differences. It is manifest, however, that he leans favour- 

 ably to the side of lateral-secretion processes, although not de- 

 fined as such. He considers both sides right and both wrong. 

 Ascensionists, he thinks, are right in deriving metals mainly by 

 ascending solutions from great depths, but wa-ong in imagining 

 these depths to be an exceptionally metalliferous barysphere, and 

 wrong in not allowing subordinate contributions by lateral cur- 

 rents from the wall-rock higher up. The lateral-secretionists, on 

 the other hand, are right, he thinks, in deriving metals by leach- 

 ing from the wall-rock, but wrong in not making the thermo- 

 sphere the main source. 



Le Conte succinctly summarises his views in the following 

 terms : — 



(1.) Ore-deposits, using the term in its widest sense, may 

 take place from many kinds of waters, but especially 

 from alkaline solutions ; for these are the natural sol- 

 vents of metallic sulphides, and metallic sulphides are 

 usually the original form of such deposits. 

 (2.) They may take place from waters at any temperature 

 ^nd pressure, but mainly from those at high tempera- 

 ture and under heavy pressure, because, on account of 

 their great solvent power, such waters are heavily 

 freighted with metals. 

 (3.) The depositing waters may be moving in any direction 

 — up-coming, horizontally moving, or even sometimes 

 down-going — but mainly up-coming, because by losing 

 heat and pressure at every step such waters are sure 

 to deposit their contents abundantly. 

 (4.) Deposits may take place in any kind of water-way — in 

 open fissures, in incipient fissures, joints, cracks, and 

 even in porous sandstones, but especially in great open 

 fissures, because these are the main highways of as- 

 cending waters from the greatest depths. 



* J. Le Conte, "The Genesis of Ore-deposits," )>. "iTC 



