|
|
| ::
Home
/ Info /
History
/ The Barberton Mining District |
* The following passage is a written
account of the area in 1951
:: Minerals and Mining
The Barberton mining district covers the magisterial districts of Barberton, portions of Carolina and Nelspruit and the northern part of
Swaziland.
:: Geology
The formations of the Barberton mining district are divided into four main groups, viz:-
1. The Swaziland System, composed essentially of a group of highly altered basic and acidic volcanic rocks and a thick succession of
fine-grained clastic sediments;
2. The Moodies System, an alternation of medium-grained and fine-grained sediments;
3. The Jamestown Igneous Complex of basic and ultrabasic rocks, which is intrusive into the Swaziland and Moodies Systems; and
4. The Archean Granite, which is intrusive into the Swaziland and Moodies Systems and the Jamestown Complex.
The rocks of the Swaziland and Moodies Systems have been intensively folded, faulted and fractured in places, as a result of the emplacement
of the Archean Granite. The rocks of the Jamestown Complex have not yielded so much to folding but they are intensely sheared.
The Swaziland System is divided into two series:-
a) The Onverwacht Series is the older and consists of basic lava, followed by some acid lava and porphyry. The basic lava has been
extensively altered to amphibole schists and the acid lava to some extent to quartz schists. The volcanic rocks are best developed in the
southern part of the area, i.e. in the valley of the Komati River and also in the Three Sisters Hills.
b) The Fig-tree Series, the younger member of the Swaziland System, consists of a thick succession of shale, slate, graywacke and banded
ferruginous and siliceous rocks, characterised by numerous thin bands of banded ferruginous chert. It is typically developed in the catchment
area of the Fig Tree Creeek.
The Moodies System is characterised by thick beds of quartzite and conglomerate which form some of the most prominent mountain ranges to the
south and east of Barberton, e.g. the Saddleback and Makonjwa Ranges. Thick beds of sandy shale separate the beds of quartzite from one
another.
The Jamestown Complex consists essentially of green and blue serpentine and a great variety of schists composed mainly of amphibole and talc.
Included in it are often found bodies of banded chert, quartzite, altered to quartz schist, and dolomite. The rocks of this Complex are
normally in close proximity to the Archean Granite and form a narrow strip between the latter and the rocks of the Swaziland and Moodies
Systems. They have without doubt been derived from a series of basic and ultrabasic igneous rocks of gabbroic, pyroxenitic and peridotitic
composition.
The granite covers most of De Kaap Valley, the area north of the Consort Mine, the upper Komati Valley and the greater part of Swaziland,
thus virtually enclosing the rocks belonging to the older groups.
In the past, gold was practically the only mineral to be exploited in this area. A study of the distribution of the existing and abandoned
gold-mines indicates clearly that the gold is not confined to any particular formation. This the Rosetta and Great Scott mines occur in the
rocks of the Jamestown Complex; Sheba, Barbrook, French Bobs and Daylight, etc., are in the Fig-tree Series, and Agnes, Alpine, Sheba, Golden
Quarry, etc., are in the Moodies System. Smaller mines have been worked in, or in the vicinity of the granite, e.g. Wyldsdale, Forbes Reef
and Oshoek. On the other hand, it had been consistently proved during actual mining that geological features such as fractures , faults,
contact zones, zones of weakness in formations, intersections of faults and fractures, and intersections of faults and fractures with
contact-zones have been of greater importance in providing suitable channels for ascending mineralizing agents than the difference in
geological formations. Thus the successful development of the Gold-mining industry in this area requires an intimate understanding, not only
of small-scale structures at each locality, but also of the broader structures of the Mountain Land as a whole. Further, in the zone of
oxidation towards the surface there occurs free gold which can be comparatively easily recovered. At depth, however, the ore turns refractory and special treatment is required to separate it from its accompanying refractory minerals.
:: Gold
After the discovery of the original Sheba Mine in 1886, mines sprang into being throughout the district. Fortunes were made and lost, but
this initial period of prosperity terminated with the discovery of gold on the Witwatersrand in the same year. The "eyes", however, had been
picked and exposed lenses were soon worked out, resulting in more difficult conditions of mining and the closing down of many mines. In fact,
of approximately 70 known gold-bearing localities only 10 to 15 mines have been in production at any one time during the past 50 years.
The life of a mine depended on a variety of factors:
1. The discontinuity and unpredictability of the ore bodies.
2. The partially or wholly refractory nature of much of the ore below the zone of oxidation.
3. The division of properties into relatively small claim areas belonging to private individuals who lacked adequate capital and technical
knowledge to exploit the properties.
4. The climatic conditions and the presence of malaria which in the early days of mining seriously reduced the habitability of the area.
... more>>
|
|
| ::
Add This
Button |
|
Are you on LowveldInfo?
Then get the code to place this button on your site here
|
|
