Manono Project Geology

Thought I might start a separate thread for those wanting  share what they have  found on the geology on Manono.

Recently came across this in my wandering on the net.

Haplo


Tin Resources Of The World


Important amounts of tin are won from both lode and placer mines
in the Democratic Repu:blic of the Congo. Tin deposits are found in
the provinces of ~{aniema, Katanga, and IGvu, and the former Territory
of Ruanda-Urundi (now the countries of Rwanda and Burundi).
The deposits are tin-bearing pegmatites, some of which are large, and
tin-bearing greisens and quartz veins; the pegmatites are more important
in l{atanga.

The basement rocks consist of a group of quartzites, schists, and
gneisses of Precambrian age, locally intruded hy mafic rocks and by
biotite granite of younger age. The tin deposits are genetically related
to the biotite granite. Columbite and tantalite are found in deeper
parts of the granites and in some placers.

The lode deposits exploited by one company ( Symetian) in Maniema
have been described in detail by Varlamoff (1948); his descriptions
are largely applicable to most of the area.

A large granite intrusion has a border of coarse-grained microcline-quartz-muscovite rock, and
an interior of medium-grained microcline-quartz-muscovite-biotitealbite
granite. Following injection of the granite, several systems of
veins and dikes formed in the following sequence: (1) Aplite-pegmatite,
(2) early quartz veins containing colmnbite and tantalite, (3)
greisen that contains columbite-tantalite and nonlithia mica, and ( 4)
greisen that contains lithia mica, wolframite, and cassiterite. Later
quartz veins contain ferberite, native his1nuth, pyrite, and arsenopyrite.
Veins are comn1onest above cupolas of granite intrusive rocks, where
tourmalinization is often intense.

V arlamo.ff considered the differing n1ineralogy of various veins
mined in the Congo to be largely a function of regional mineral zoning
com.bined with the depth of erosion. In upper (or outer) zones, greisen
deposits that contain cassiterite and sulfide minerals are important. In
deep zones within granite, veins contain important amounts of columbite-
tantalite in addition to cassiterite.

In Katanga, large pegmatites are mined by open-pit methods. The
~Ianono pegmatite is about 10 km long, as much as 400 m wide, and
contains cassiterite throughout (Geomines Co., 1967, p. 3). Cassiterite,
which is present in amounts averaging about 2.2 kg of tin per cubic
meter, is accompanied by thoreaulite ( SnTa20 7), in the ratio one part
thoreaulite to 20 parts cassiterite. Ore minerals recovered are cassiterite,
tantalite, columbite, and thoreaulite.

Spodumene is an important constituent of the pegmatite, but it is not routinely recovered.
The Manono pegmatite produced 127,500 metric tons of cassiterite
from about 1928 to 1967 (Geomines Co., 1967, p. 4). Other pegn1atites
in the Congo are worked on a smaller scale.
Placer deposits of cassiterite in the Congo are mainly small but
rich. The deposits are localized near biotite granites, or where streams
cross tin-bearing greisens or pegmatites.
Reserves.-The Democratic Republic of the Congo government estimated
reserves for Robertson's report ( 1965, p. 84), and these figures
are presented in table 10.
Robertson presented evidence to show that these reserve figures are
extremely conservative; the writer agrees. For instance, measured and
inferred reserves in the Manono pegmatite (Manono and IGtololo
mines, to a depth of 125 ft) 'are estimated by the writer to be about
900,000 short tons of tin metal.

Total reserves in the Democratic Republic
of the Congo therefore are estimated to be at least 1 million long
tons of tin1netal, most of which is in the Manono pegmatite.

Resources.-As emphasized by Ahlfeld (1958, p. 52), the Congo
tin fields were not discovered until 1933, and tin-bearing granites and
pegmatites are widespread over many thousand square miles. The tin
fields therefore are not yet considered to be completely explored. For
the present report, the writer assumes that tin resources in submarginal
and undiscovered deposits amount to another 1 million long tons of
tin metal. This estimate probably is conservative. Thus, the Democratic
Republic of the Congo contains one of the major tin reserves of the
world.