(^i^ PROCEEDINGS OF THE SATXT LOUIS MEETING 



Discussion 



Dr. A. P. CoLEMAX congratulated Mr, Ekblaw on showing how large a field 

 for geological work still remains open in the Arctic islands. On the main- 

 land, in Labrador, there is also much room for work. Two summers' work have 

 shown a large area in northeastern Labrador that was not covered by the 

 Pleistocene glaciers, as in some areas which he has mentioned in the far north. 



Dr. E. O. HovEY : Mr. Ekblaw's trip across Grant Land and results obtained, 

 Including collections, testify to the value of the geological observations made 

 in connection with the Crocker Land Expedition. 



In his reply the author emphasized the desirability of establishing a scien- 

 tific station in Labrador. 



GEXESIS OF MISSOURI LEAD AND ZINC DEPOSITS 

 BY W. A. TARR^ 



( Ah s tract) 



A review is made of the current views that the lead and zinc deposits owe 

 their origin to circulating ground waters which obtained the metals from the 

 dolomites and limestones of the Ozark area or from once overlying, but now 

 removed, beds. 



There are serious objections to these views, among which are the amounts 

 of the metals in the original rocks, their distribution in them, their relation- 

 ship to the solution channels, and the character of the circulation of the 

 ground waters and its quantitative possibilities. Results of recent studies in 

 related subjects offer new evidence which favors the view that they were de- 

 posited by rising thermal solutions. 



Eead in full from manuscript. 



Discission 



Dr. A. R. Crook : Has the author not underestimated the permeability of 

 rocks, illustrated by the treatment of agate in commercial manufactures? 



Dr. W. H. Emmons stated that he had proved the considerable permeability 

 of some igneous rocks by soaking them in red ink. Does pyrrliotite occur as 

 reported by Winslow? 



The author replied that linnseite occurs and has been mistaken for pyrrlio- 

 tite. Hydrothermal action has been noted. Permeability has been studied. 



Dr. F. R. Van Horn : Doctor Tarr seems very certain that the Missouri zinc 

 and lead deposits were derived from igneous rocks and brought to their present 

 position by ascending waters. This non-argentiferous type of deposit is found 

 in three different parts of Missouri, from the upper Mississippi Valley in Illi- 

 nois, Wisconsin, and Iowa, from Belgium and western Germany, and from 

 Silesia, Galicia, and Poland. At all of these places the ores are associated 

 with dolomitic limestones of Cambrian, Ordovician, Mississippian, and Triassic 

 age. Small amounts of sphalerite are found in the Niagara limestone in Ohio, 

 and galena occurs in the Lockport dolomite in Ontario, these rocks being of 



Introduced by E. B. Branson. 



