The
area examined, and herein described, of the Egerton-Gordon Gold-field,
extends from the southern boundary of the field inspected for the Rocky
Lead report,* for about 17 miles south through Bolwarrah, Summer Hill,
Gordon, Egerton, the Moorabool and Mount Doran, and has a width, east
and west, of about 5 miles. There has never been much mining on its
extensive systems of lodes, excepting at Egerton itself, and at Gordon,
in which places works were opened in the early fifties on outcrops of
quartz rich in gold, and taken to depths from which, in all, more than
2o tons of gold have been won.
As
usual in the gold-fields of this State, the quartz lode systems are in
sedimentary rock, the original layers of which have been much crumpled
and corrugated. This rock is composed of the usual fine-grained
gold-slate, and fine-grained sandstone, up through the cracks in which
have been forced various kinds of hot fluid dyke material.
The
region examined is really a north-and-south range of sedimentary rock
resting on granite, which outcrops through the former on its western
side. This granite appears to have had much to do in the crumpling and
corrugating of the sedimentary rock layers, and in sending up a "
perspiration" through the latter's cracks in the form of the hot fluid
material above mentioned. The granite outcrop appears to be on the
eastern slope of a great wave of this rock, the western slope of which
descends towards Ballarat from Warrenheip, 8 miles to the west of the
line traversed.
Along the line of the area under notice are several volcanic mounts, and thousands of acres of. rich volcanic soil.
Most
of the 4 or 5 miles thick of sedimentary rock, which the granite
appears, as it came slowly upwards, to have displaced and crumpled, has
been removed by the wear of ages from this 5 miles in width of country.
In fact, this width represents a pre-historic valley with several minor
valleys whose streams cut through terraces of bouldery wash-dirt down
to the granite. Dividing these valleys were remnants of the crumpled
and corrugated beds of sedimentary rock, in the form of ranges similar
to, but smaller than, the Egerton-Gordon range.
In
due course there came the later volcanic eruptions, and the whole of
this valley, from Warrenheip to Egerton, was made a dumping ground for
the "run" of molten and muddy material ejected from deep cracks in the
earth. This volcanic activity appears to have been very general all
over this region on more than one occasion, and really prepared the
region of Egerton, Gordon, and Bungaree for the farmer.
The
aqueous circulation in the crust of the earth to which we trace the
origin of our lode formations, has been described in previous reports,
if in which it was explained, inter alia, that, as deposits of
dyke material and lode material are from liquids circulating in the
same systems of cracking, all lode systems are dyke systems and all
dyke systems are lode systems. This applies, at least, to all the
formations met with in my inspections of the
* Bulletin Geol. Survey Vict., No. 3 (1903). t Bulletins Geol. Survey Vict., Nos. 2-7. .
[lleport sent in 28tk March, 1903.]
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