Oulmes Sector (Sn-W)

KINGDOM OF MOROCCO
OULMES SECTOR (Sn-W)
(Central Hercynian Massif, Morocco)
February 2016
KEY POINTS :
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Mineralization related to the Oulmes Hercynian granite in the Central Massif.
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Mineralization as Sn and W in quartz veins and placers.
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Interesting average contents of Sn and W.
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Easy access near the road linking Oulmes to Rabat and Khénifra.
GEOGRAPHICAL FRAMEWORK:
The Oulmès prospect is located about 10 kilometers west to the Oulmes city (Fig. 1 and 2).
Access from Rabat can be done through road Tiflet, Mâaziz Tiddas over 150 km.
The Oulmès sector depends administratively of the Khemisset province. It is covered by seven
licenses on the 1/100,000 topographic sheet of Moulay Bou Azza Oulmes.
Figure 1- Map location of the Oulmès sector
Figure 2: Location of the Oulmès sector's licenses
REGIONAL GEOLOGY AND MINERALIZATION :
The Oulmès Granite, of Hercynian age, outcrop as a dome (9 km x 4km) in the schists, quartzites and
sandstones of Ordovician age and is part of the khouribga - Oulmes anticlinorium (Fig. 2).
Figure 2: Mining licenses and known shows location in the Oulmes sector
Extracted from the 1/50000 Oulmes's geological map
This granite is known for its tin and tungsten mineralization. The mineralization consists of
cassiterite and wolframite, generally confined to quartz veins.
The main vein fields that have been the subject of exploitation in the middle of the last century are
those of El Karit (Sn) and Zguit (W). But other veins or placers shows are known in the granite.
In the vein field El Karit, a program of work was carried out by ONHYM in the 1980s and 2000s
with trenches, core drilling and galleries.
The Tafer El Haj show is in the form of a swarm of quartz veins hosted in the northern part of the
granite. The Tarmilat show is also in the form of a swarm of veins and veinlets with varied
mineralization that stretches from the village of Tarmiat to Oued Boulahmail at the south.
The land is covered generally by topsoil and granitic sand dotted by millimetric fragments of
cassiterite. The work done by ONHYM in 2006 and 2011 has outlined some tin-bearing placers in the
northern part of the Oulmes granite.
ONHYM'S WORKS ON THE OULMES SECTOR :
El Karit tin deposit
The El Karit tin deposit is represented by quartz veins in the west contact of Oulmes granite over an
area of 200 to 300 m wide and 2 km of extension (fig.3).
The tin mineralization related to Oulmes granite, is represented of cassiterite localized in the wall rocks
of the veins that have undergone a kind of greisenisation with mostly muscovite, feldspar and beryl.
Cassiterite crystals are observed as inclusions in quartz mass in the middle of the vein. On wall rock
schist veins, there is a tourmaline development that is characteristic of the metasomatism in the
schists.
Figure 3: Quartz vein field of El Kari deposit (Termier, 1950)
Research work by trenches, small galleries and drilleholes were carried out especially in the two old
workings sites called Marsouin II and Hirondelle I. A total of 15.3 m3 of trenches, 118.4 m of galleries
and 5 diamond drilling totaling 710.3 m were performed, with the collection of 243 samples from
surface and 357 from cores.
At Marsouin II , three vein structures oriented NE and named M1, M2 and M3 were followed by
galleries respectively on 20, 50 and 20 m. Their average thiknesses are 0.73, 0.49 and 0.46 m, and
their respective average grades are 0.54, 0.33 and 0.35% Sn. The three structures, considered
together, have an average thikness of 0.53 m and an average grade of 0.40% Sn.
At Hirondelle I, two vein structures oriented ESE and named H1 and H2 were followed by galleries
respectively on 24.4 and 4.0 m. H1 structure has an average thickness of 0.98 m and an average
grade of 0.96% Sn; for H2 structure, the respective averages of these parameters are 0.39 m and
1.90% Sn. On this site, 15.3 m3 of trenches were performed, showing veins witch thicknesses and
average grade are respectively 0.74 m and 0.88% Sn.
At Hirondelle I, 3 diamond drilling totaling 440.80m were performed (Figure 4 and 5). They intersected
a vein field over a width of 52.7 m. The cumulative thickness of the quartz veins in this field is
estimated at 4.7 m, representing 9% of the thickness of the vein field. The average grade of impacts in
the drillholes is around 0.25% Sn.
Two other diamond drilling, EKS.3 (154.60m) and EKS4 (114.90m), were executed respectively at
Marsouin II and Hirondelle II. They gave intersected two exceptional grades of 20.7% Sn over 10 cm
and 8.7% over 10 cm.
Figure 4: Location of drillholes in the Hirondelle I site
The resource assessment concerns only and Hirondelle I because it presents the best results in
surface and sub-surface and on which the most drillholes were executed.
Evaluation of Hirondelle I resources gave 622 750 t at 0.6043% Sn. This assessment is made on the
basis of data of mining works and drilleholes.
Figure 5: Interpretative section of the drillhole EKS.1 performed at Hirondelle I
Zguit tungsten deposit
The plateau of Zguit is located south-west of the Oulmès Hercynian granite (Figure 2). It consists
of the formation of "flagstone schists" of the Ordovician. This formation is composed of alternating
argillaceous siltstones, mudstones with silty laminas and sandstones. It contains multi metric bars of
quartz sandstone (Figure 6). A bundle of quartz veins mineralized with wolfram with northwest general
direction, intersects the shale and sandstone formation. Veins trend along faults which sometimes shift
vertically the granite.
The vein 5 has been the subject of a great amount of work. It consists of two distinct parts:
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The first part in the southeast has an extension of 300 m with a thickness of 40 cm and a
grade of 0.25% WO3. Mineralization consists of wolframite and a little scheelite.
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The second part or "west lode" is the most important. It follows discontinuously south-east to
north-west over 850 meters and has a thickness of approximately 40 cm and a dip of 70-80°
toward the southwest. Mineralization is characterized by the appearance of more and more
scheelite to north-west.
Figure 6: Geological map of the Zguit vein field
The history of research work carried out on Zguit can be summarized as follows:
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From 1949 to 1959, the company Wolfram Zguit exploited a panel between the level 1002 and
the surface corresponding to the zone of maximum mineralization representing a vein cube of
460 m3 where it was removed 7.3 tonnes of WO3, which corresponds to a recovered grade of
0.6% WO3.
From 1961 to 1962, ONHYM rehabilitated the shaft n°3 and made an underground and
surface sampling, results were positive.
In 1969, ONHYM performed the sinking of the shaft n°3 from 50m to 90m and tracing in the
level - 80.
In 1980, ONHYM performed 4 drill holes in order to reach the vein leached below the water
table at a depth of 140m. These drill holes have highlighted the vertical discontinuity of veins.
Only work done in 1961-1962 and 1969 show some resources on the "west lode" section of the
vein N° 5, evaluated to 13 680t with an average grade of 0.76% WO3.
PERSPECTIVES :
For further research, exploration has to be continued especially in the vein field of Zguit where
several veins favorable to the tungsten mineralization require further work.
To the north, other placers could be developed, as well as quartz veins with cassiterite
detected in the wadis.
For further information, please contact:
Mme Amina BENKHADRA
General Director
5, Avenue Moulay Hassan- BP 99 - Rabat, Morocco
Tel. : + 212 5 37 23 98 98 – Fax : + 212 5 37 70 94 11
E-mail : [email protected]
Site web : www.onhym.com