really
is the northern continuation of the channel of golden drainage, and
when one notes the nature of the lode structure hack south down this
line of gold, when one considers how the twist strain applied to the
field generated a lengthy series of wing cracks (as in Fig. 4), it
seems remarkable that attention was not directed south on this
gold-slate line of drainage at the 1,700-ft. level, that the floor now
being driven for at the 1,108-ft. level might be cut, or, if not that,
another of the same series. Just about here, in the neighbourhood of
the main shaft, a break, filled with dyke material, said to be
decomposed basalt, is to be seen. It outcrops a little to the north of
the shaft, dips to the north at an angle of about 22° from the
vertical, and runs north-east by east. It is one of the later breaks in
the corrugated rock beds, those that contain quartz known as vertical
"makes" and "wings'" being the earliest, the series of breaks running
north-east and underlying south-east coming next, and this last, almost
east and west, one being the latest. They are all due to the
application of tangential thrust, and each has been brought about, in
relative order, as the dying spasms of a great movement adjusted the
rocks in these parts. There is no telling how much of the earth's crust
containing part of this system of cracking, with its lode and dyke
material, has been washed or worn away during the ages since the first
series (the dykes and lodes) were originated. How far the wear of ages
has brought surfaces down into a favoured situation of golden " filter
packs " of quartz it is hard to say.
Observation
in this direction leads me to suppose that at Egerton not more than
1,000 feet in height in some parts, and considerably less than that
height in others, of the favoured situation opened here, has been
removed. The mining works of the past have been taken in more than one
place to the lower part, of the main gold situation, and on to the top
of another situation, which will be found to have a more nearly
vertical structure of lode, and a less width of quartz, in " makes"
more continuous in length and depth, and having their wealth in gold
more evenly distributed. This change in lode-structure is due to the
difference in the direction of the thrust of the force relative to" its
resisting point as a greater depth was reached from the surface at the
time the cracking in the earth's crust was brought about. Such
alterations in lode-structure do not always show a change from thick
bunchy occurrences to long thin occurrences. In Ballarat West the
reverse change in structural arrangements of its lode bodies is to be
seen. In the present Band and Loch mine, Ballarat West, the lode that
came down in the late Loch Company's area as a narrow well-defined
formation of, for the most part, book-like quartz, containing gold
fairly evenly distributed down its full extent, I found to be
associated with many lines of nearly vertical drainage in the slate of
its country. This was so down to the 1,800-ft. level, below which
further sinking by the Band and Loch, after the amalgamation of the
companies, brought to light a different lode-structure altogether, the
narrow stone giving place to great, bulging widths of stone, which are
evidently the top of a series of such formations that will be found, no
doubt, to extend for another 1,000 feet or more in further depth. At
the Birthday mine, Berringa, a similar state of affairs is to be seen,
the structure showing a change from long narrow lines of quartz to
comparatively short and wide formations of quartz. Here in Egerton the
works have been taken down to the lower part in the " bulge-make"
structure, and, in some parts, into the higher section of one of the
comparatively thin " makes " of lode structure which follow in
alternate order with the systems of wider " makes " to great depths.
Remaining
below the Sister Rose and Rose workings are great extents of the wing
series of quartz formations, not only of the one mined down to
