Wingayongo Epithermal Prospect.
Introduction.
Wingayongo is best
known as the site of a core hole drilled by British Petroleum - Shell in
1954 to a depth of 762 m to test tstratigraphy and structure associated
with altered, bituminous, sulphur - bearing sandstones and nearby
sulphurous hot springs. Wingayongo Hill is an isolated hill rising 20 m
above featureless flats north of the lower Rufiji River and northeast of
the town of Utete (Fig.38) at 38 degree 24'E, 7 degree 49'S. Abundant
signs of hydrothermal alteration were noted in portions of the core, which
were described by Mclean (1955). Carter (1961) reported on the
mineralisation.
Geology and Mineralisation.
Wingayongo Hill is
made up of Cretaceous or Jurassic Fluvial sandstones. Boulders on the
slopes of the hill show various types of alteration: fracture coatings,
impregnations, vugs filled with sulphur and bitumen, silicified boxwork
texture fracturing and possibly kaolinisation.
The Nyangoni hot
springs a few kilometres to the southwest emit gas and hot saline water.
Tufa cones of calcium carbonate, possibly with some sulphur, are built up
around some of the springs.
It is surmised
that the hot springs and Wingayongo Hill occur along northeast - trending
faults, which are otherwise obscured, by young sediments and sheet wash.
The drill hole
(Wingoyongo No.1) showed a water temperature of 61 degree C at 64 m depth,
and encountered sporadic signs of hydrothermal alteration, especially
between 47 and 125 m.
Signs of
alteration included:
● bitumen above 47
m depth;
● cinnabar at 47
57m;
● fluorite at 99 m
and below;
● silification,
pyrite, arsenopyrite, chalcopyrite, barite, and pyrrhotite at various
depths;
● pyrite cubes up
to 5 cm across;
● steep fractures
in some of the core;
● clay coatings on
fractures
Carter (1961)
concluded that the fractures in outcrop, in the core and at the hot
springs were strongly indicative of former hot spring activity. He
recommended drilling the area as a mercury prospect, but this was never
done. There is no record of any chemical analysis.
Exploration
Opportunity.
The Wingayongo
alteration and mineralisation (Fig.39) fit the classic description of
shallow epithermal and hot - spring precious metal deposits (Cox and
Singer, 1986, model 25a).
Wingayongo is a
project for hot spring or shallow epithermal gold - silver mineralization.
Surface sampling and shallow drilling would be the logical first steps in
evaluating the prospect. James (1967) describes hot springs in Tanzania.
IN 1995, Patrician Gold Mines, in a joint venture with Sampo Resources,
drilled an inclined core hole beneath the Siliceous Cap at Wingayongo.
Pyrrhotite and various forms of alteration were encountered.