A sedimentological study of the conglomerates in the Elsburg stage on the Welkom and Western holdings gold mines
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Date
1970-12
Authors
Kleynhans, Jacob Johannes
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
A sedimentological description of the layers of conglomerate
in the Elsburg Stage of the Witwatersrand System, as disclosed
by 23 boreholes and underground development on the Welkom and
Western Holdings Gold Mines in the Orange Free State Goldfield,
is given.
The palaeocurrents in the Elsburg Stage as inferred from
pebble-size distribution and preferred pebble orientation, were
from two different directions. On Western Holdings Limited and
the Welkom Mine area west of the Arrarat Fault, the layers of
conglomerate were derived from the north-west. On the Welkom
Mine area east of the Arrarat Fault, the direction of transport was
from the south-west.
These two different palaeocurrent directions can be explained
by lateral movement along the Arrarat Fault. Thus, the eastern
block of the lease area of the Welkom Gold Mining Company, which
was formerly situated on the north-eastern flank of a delta fan,
was displaced along the strike of the Arrarat Fault for a distance
of approximately 6 000 m towards the south, while the western
block (Welkom No.3 Shaft and Western Holdings Limited), was
displaced towards the north.
A detailed analysis regarding the composition, roundness,
shape, orientation and sorting of the pebbles in the layers of
conglomerate was undertaken. The sorting and roundness of the
pebbles increase towards the centre of the basin, while the
majority are orientated with their long axes parallel to the
palaeocurrent direction. The percentage of non-durabIe pebble
types also decreases in a down-current direction, while the
durable types remain constant. The pebbles are mostly
spheroidal, although certain types show a strong tendency to
disc shaped. These features indicate that the layers of
conglomerate were probably deposited on an alluvial fan
bordering an inland lake or sea.
Description
Keywords
Gold mines and mining -- South Africa -- Free State -- Welkom, Sedimentology, Dissertation (M.Sc. (Geology))--University of the Free State, 1970