western
gold-fields of the State, and described in previous reports. Here, on
the Egerton-Gordon run of gold-bearing sedimentary rocks, the dyke
feature is very pronounced, and it may be said that the whole of the
lode systems within the 17 by 5 miles traversed are associated with
pronounced dyke occurrences, classed variously as elvanite, basalt,
diorite, and felsite. The main lines of drainage are as usual between
the arches, which strike about 10° west of north and lean a little to
the west, that is, underlay to the east. Considerable twist strain has
been applied in producing the corrugation of the mass of slate and
sandstone country, and this has resulted in a system of cracks, having,
as usual, almost vertical passages, associated with which are great and
small wing and fin-like cracks, all of which contain quartz or dyke
material, often both. The greatest intensity of the twist strain to the
corrugated strata appears to be in the locality of Egerton itself, and
thence south to and over Mount Doran. North from Egerton there appears
to be a a lesser twist effect in the lode structure, while in Gordon
and for miles to the north the twist effect to be seen in the lodes is
still less. As we get further north, through Bolwarrah, and on towards
Korweingnboora, the main lodes are, as a rule, void of wing and fin
appendices, but the dyke material is present on all formations
throughout the line.
In
describing past and present mining within the area under notice. I will
commence at the southern end and run through the line north to the area
described in the Rocky Lead report. Mount Doran is situated from 6 to 8
miles to the south of Mount Egerton, and some 4 or 5 miles to the north
of the gold-field of Elaine. It is composed of high ranges of
gold-bearing sedimentary rock, and is bounded on the west by the town
of Lai Lai, on the south by the Elaine and Dolly's Creek gold-fields,
on the east by the Little Forest and the Moorabool (known locally as
Bungeeltap and Bun gal), and on the north by Mount Egerton itself. At
Lai Lai are immense deposits of granite clay, suitable for the
manufacture of ornamental white bricks, tire bricks, gas retorts, and
all kinds of assay utensils. There is also a large deposit of white
clay used extensively in the manufacture of domestic delf. and in
giving a body to certain kinds of paper. The well-known deposit of
lignite is associated with a heavy blue fire-clay suitable for the
manufacture of bricks to be used in furnaces of changing temperature,
and near at hand there is a deposit of blue clay which fluxes at a low
heat, and is suitable for the manufacture of stoneware of all
descriptions. North of Lai Lai, and near the Falls, is an outcrop of
felspathic rock, south-east of which, on Mount Doran itself, is a large
deposit of iron ore. The Mount Doran range is really a continuation
south of the Egerton-Gordon range, and its lode structure is. as
mentioned, due to much twist strain imparted during the corrugation of
the rock beds. Mount Doran has many systems of quartz lodes running, as
usual, a little west of north, encased in gold-slate having many lines
of drainage, and all are associated, more or less, with dyke material.
There has been no mining on any of their lines, with the exception of
surface " rooting," here and there, at points where surface wear had
exposed favoured situations in which the gold could be seen. The latest
of these attempts at mining was made on a lode known as the Mount
Doran. Here a wide formation, of low value in gold, was found to have a
layer of quartz, a foot in width, on its hanging-wall side. This narrow
stone proved to be payable in parts. It represents the original
drainage passage of the lode, the wide footwall stone being apparently
a secondary deposit—an enlargement, such as would be produced if we
were to run boiling sugar through cracked biscuit. The biscuit on the
sides of the cracks would flake off and become incorporated in the
sugar, and thus a gradual enlargement would take place. All quartz
lodes appear to have been enlarged in this manner.
