308 H. I. JENSEN. 
and perhaps also the cause of the dislocations may be a 
great laccolite of quartz diorite intruded at a great depth. 
In the Endrick River I have seen quartz-diorite traversed 
by veinlets of mispickel and blende. The cooling ofa huge 
mass of such rock might well have given rise to large ore 
deposits in overlying strata into which hot solutions rose 
from the shrinking mass. Certain it is that the Kttrema 
deposits are not contact deposits, nor are they segregation 
veins, for no rocks occur anywhere in the vicinity which 
contain their mineral contents. The only igneous rocks 
which I have seen cutting the Devonian rocks in the 
Ettrema gorge are a thin dyke of decomposed (chloritic) 
andesite, less than a foot wide, and a couple of diorite dykes. 
The solutions which brought the minerals to the surface 
must have consisted of alkaline sulphides, sulphuretted 
hydrogen, silicic acid solutions, for they strongly interacted 
with the limestone with the result that great thicknesses 
of what was originally limestone has been turned partially 
or wholly into chert. 
The entire geological surroundings indicate that the two 
fissure lodes will widen and meet at depth, their joint pipe 
still widening until the base of the limestone is reached, 
inasmuch as in the limestone solution and replacement have 
taken place on the walls. The base of the limestone will 
be about 600 feet below the bed of the creek at the mine. 
After that in the subjacent slaty and schistose rocks the 
lode will become somewhat narrower and probably richer 
in the more valuable metals (Ag., Au., Cu. and Pb.) and 
arsenic until the source isreached. Whether an ore deposit. 
of such a complex character and situated in so awkward 
a place will pay to work in our time is a question which 
must be left to time and to mining engineers to solve. 
Results:—1. It has been shown that the country between 
the upper Shoalhaven and the sea is a raised plain of 
marine sediments and probably not a raised peneplain. 
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