﻿Bonk Noficfs. 201 



interesting papers are also to be found among the proceedings of 

 the different sections. 



Speaking of the disruption and elevation of strata in the 

 Permo-Carboniferous age (Gympic beds) when the more important 

 Auriferous deposits of both the eastern and western parts of the 

 continent were formed, Mr. Gregory says in his inaugural address : — 

 There was not only great disruption of the strata, but igneous rocks 

 forced themselves into the fissures of the sedimentary beds, and the 

 resulting metamorphism of the adjacent rocks increased the confusion, 

 as beds of slate may be traced through the transformation of their 

 sedimentary character by the recrystallisation of their component 

 elements into diorites, having that peculiar structure of radiating 

 crystals which usually characterises rocks of volcanic origin. As 

 regards the Auriferous deposits in these lodes, it appears that the 

 simple fissures were filled with water from the ocean or deep-seated 

 sources ; but in either case the powerful electric currents which 

 continually traverse the earth's surface east and west met resistance at 

 the lines of disruption, and electric action being developed the 

 mineral and metallic salts in the water in the fissure and the adjacent 

 rocks would be decomposed, and the constituents deposited as bases, 

 such as gold and silver, or as compounds, such as quartz, calcspar, and 

 sulphide of iron, all which were in course of deposit at the same time, 

 as the angles of the crystals cut into each other. The theory of 

 thermal springs is contra-indicated as the lime appears as calcspar, 

 a form occurring in cold solutions and not in the form of Aragonite as 

 in hot solutions. There have been many speculations as to the 

 sources from which the gold was derived, but that which best accords 

 with the actual conditions is that the metal exists in very minute 

 quantities in the mass of the adjacent rocks, from which it has been 

 transferred through the agency of electric currents and the solvent 

 action of Alkaline Chlorides, which dissolve small quantities of 

 the precious metals, and would l)e subject to decomposition at the 

 places where fissures caused greater resistance to the electric current. 

 One remarkable circumstance is that the character of the rocks 

 forming the sides of the fissures has an evident influence on the 

 richness of the ores in metal, where lime, magnesia, or other alkaline 

 compounds or graphite enter into their composition, the gold especially 

 is more abundant than where the rocks contain silica and alumina only. 



In Queensland, Gympic affords some instructive examples of fissure 

 lodes. In some large masses of rock have fallen into the fissure before 

 the ore was deposited, and have formed what miners term " horses," 

 where the lode splits into two thin sheets to again unite below 

 the fallen mass. . . . The ore was originally an auriferous pyrites, 

 but the sulphide of iron was largely decomposed, leaving the gold 

 disseminated through the oxide of iron. 



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