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THE BERRINGA GOLD-FIELD.
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The
Berringa Gold-field is situated about twenty miles to the south-west of
Ballarat city, and extends from Rokewood Junction on the south, for
about twelve miles north, to the old alluvial diggings near Scarsdale.
It includes mining •centres known as Newtown,. Staffordshire Reef,
Kangaroo (now known as Berringa), Moonlight, Misery Ranges, and
Rokewood Junction. Sixteen months ago I examined and reported on the
gold-bearing features of a strip of country east of, adjoining, and
parallel to this area.* The whole district is composed of ranges cut in
the southern part of the Ballarat plateau by water action. Its highest
altitude above sea-level is about 2,000 feet, while the volcanic plain
seven miles to the south of the town of Berringa has an altitude above
sea-level of about 600 feet. Its country is composed of the usual
sedimentary rock peculiar to most of our gold-fields. This is classed
by geologists as ordovician (lower silurian). Its layers of sandstone
and slate, originally nearly horizontal in their bedding, have been
corrugated, and have the lines of (he arches and troughs running
generally about 10 deg. west of north. In places they run as much as 30
deg. west of north. The arches lean a little to the west in parts of
the field, and in others a little to the east. They appear to zig-zag
down somewhat as in Fig. 1.
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There
seems to have been great pressure applied to the field from the north
and south, which is responsible, no doubt, for the irregularity in the
stratification of the rock layers. As noticed on the other gold-fields,
the whole of the country has been much fractured. This fracturing was
produced as the corrugation of the field was in progress, and, of
course, it followed along lines of least resistance to the forces that
caused it.
Much
of the vertical irregularity in the arches appears to have been brought
about as the mass settled down after its corrugation. The fracturing of
the rock lavsrs could only occur where they were sufficiently cool to
be crisp enough to be fractured. At depths, the intense heat would
render them liable to be bent rather than cracked. In this zone of the
earth's crust, water would exist as we know it. Below it, it would
exist as vapour or dry gas. It is reasonable to suppose that the heat
of the mass in its lower portions diminished the influence of the
gravity " pull" on watery liquids as they moved down. Water will be
water as long as heat allows it to be so; but water could not exist as
such in a region having a temperature sufficiently high to render the
rock mass pliable, or below, it is estimated, about 35,000 feet from
the surface. The depth of this
* Geol. Survey of Victoria, Bull. No. 4 (1903), The Enfield Gold-field.
[Report sent in 7th November, 1903.] 1179.
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