ORE DEPOSIT THEORIES. 205 
SOME MODERN THEORIES CONCERNING ORE 
DEPOSITS. 
Ls 
By G. A. Water, Assistant Government Geologist, 
Tasmania. 
THERE is perhaps no branch of geological science upon which 
more difference of opinion exists, than upon the origin of 
ore deposits and the various phenomena connected there- 
with. Nevertheless, our knowledge has advanced very rapidly 
during the last ten years, probably more so than during any 
like period of the past. Many new and brilliant theories have 
been evolved, and older maxims have had to adjust themselves 
to our extended knowledge. In the present paper I pro- 
pose to discuss some of the modern theories of the origin of 
ore deposits, and in doing so will base my arguments as 
much as possible on the occurrences of ore deposits in Tas- 
mania, than which, I venture to say, there exists no more 
fertile field for the investigations of the mining geologist. 
The condition of the science of the origin of ore deposits 
at the present day may be fitly compared to a region under- 
going intense metamorphism; new facts are being added 
to our store of knowledge, and old ones are acquiring a new 
and more significant aspect. Matter which for years has 
lain m a clastic condition is gradually undergoing recon- 
struction, and crystallising into definite forms. 
The most prominent feature in the progress of the science 
during the past decade is the advance made by the new 
school of geologists who, following de Launay and Vogt, 
attribute a plutonic origin to the majority of ore deposits. 
During the heated discussions which took place in the pre- 
vious decade, when Sandberger championed the cause of 
lateral secretion, and Stelzner and Posepny so vigorously 
defended the old ascension theory, it would have been diff- 
cult to realise the complete change of position which the 
two schools were to occupy at the present day. The lateral 
secretionists abandoned the main positions occupied by Sand 
berger, and eventually evolved a theory which differs not very 
greatly from the old ascension theory. We may describe this 
school as the ‘‘ meteoric school,” since it attributes the con- 
centration of ores to the action of circulating meteoric waters. 
Many, perhaps the majority, of the old ascensionists joined 
the ranks of the meteoric school, but not all—the remnant 
adopted a new line of enquiry. Basing their investigations 
upon the almost universal association of ore deposits with 
eruptive rocks, and aided by the rapid advance made in the 
