Lopo Vasconcelos
Dept. Geology
Eduardo Mondlane University
Maputo, Mozambique
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
1. INTRODUCTION
Located in Southern Africa;
+800.000 km2
Complex geo-tectonic framework, ageing from Meso-Archaean (2907 My) to Quaternary.
Karoo Supergroup (KSG) ð significant coal deposits.
KSG presents generally 2 main episodes:
sedimentary formations: U. Carboniferous – L. Jurassic
– graben & half-graben basins
igneous formations: simultaneous with topmost
Upper Karoo sediments – L. Jurassic
Irregular distribution of KSG:
Only igneous episode:
Libombos monoclinal and Angoche Basalts
Only sedimentary formations:
Metangula and other Niassa and Cabo Delgado grabens
Areas where both exist
Tete and Center
Main coal occurrences
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2. GEOLOGY OF THE MAIN MOZAMBICAN KAROO BASINS
Geology of coal basins very diverse:
Widespread geographical locations
Different geologic/tectonic
frameworks
Different sedimentation environments
Different evolution histories
Different coal types/qualities
Age: Upper Carboniferous – Lower Jurassic
Thick sedimentary sequences deposited in continental basins
KAROO:
Strata unconformably overlying the Precambrian basement
followed by bimodal igneous formations of Lower Jurassic age
and/or unconformably overlain by Middle Jurassic or younger
strata.
Bimodal Igneous formations
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2. GEOLOGY OF THE MAIN MOZAMBICAN COAL (KAROO) BASINS
SEDIMENTARY
IGNEOUS
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2. GEOLOGY OF THE MAIN MOZAMBICAN KAROO BASINS
Karoo basins geodynamically subdivided into (Hobday 1986 in Cairncross 1989):
Foredeep basins
Intracratonic sag basins
Rifts
Mozambique: Grabens/Half-grabens
In general:
more arid and warm conditions
fluvial/lacustrine clastic sediments
(COAL)
sediments of glaciogenic/
/temperate and deltaic origin
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2. GEOLOGY OF THE MAIN MOZAMBICAN KAROO BASINS
Zambezi Valley: divided into W and E areas, separated by Precambrian rocks in Songo area.
Western: E-W trend;
Eastern: NW-SE trend;
correspond to the Zambezi Mobile Belt between the Zimbabwe & Congo Cratons.
Each of these areas: subdivided into structurally controlled smaller sub-basins.
Three main basins:
Chicôa-Mecúcoè
Sanângoè-Mefídezi
Moatize-Minjova (NW and SE
extensions to Nkondezi and Mutarara)
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.1. KAROO IN METANGULA BASIN (Niassa)
No evidence of basal conglomerates of glacial origin (Dwyka);
Outcrops of Ecca (coal)(Permian) and Beaufort (Permo-Triassic)
restricted to the southern tip of the basin
Oriented NE-SE, border faults
NW-SE faults: Rio Moola and Txiune Faults
Verniers et al (1989) – Beaufort up to 600 m thick
Upper Karoo up to 6 km thick
Ecca: - subdivided into 3 horizons: K2, K3 and K4.
K2
local basal conglomerates, coarse grained gritty
sandstones, siltstones, mudstones and thin coal beds.
343 m
Coal beds avg. 20 cm in a sequence 17-26 m thick.
K3
no coal, cross-bedded sandstones with intercalations of
siltstones and mudstones.
K4
coal present amidst cross-bedded sandstones.
two coal-bearing series
Ø1-4 m thick
Upper
Øcoal seams 67-100 cm thick
Ø1-4 m thick
Lower
Øcoal seams 110-272 cm thick
Beaufort: argillaceous siltstones & reddish silty argillites,
several levels of reptile fossils.
Upper Karoo (Triassic-Jurassic): sedimentary rocks
forming fluvial cyclic sequences, contemporary with the
graben subsidence.
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.1. KAROO IN METANGULA BASIN (Niassa)
VPDM (2012)
There are seams with small coal proportion (N1C1: 29% coal).
Total thickness: 96.2 m
Sterile layers: 65.4 m
(68%)
Coal 30.8m
(32%)
Sterile
16.4 m
Coal
14.4m
15%
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.2. KAROO IN TETE
Border faults parallel to Zambezi Mobile Belt
Faults filled with dolerite dykes (igneous
episode
Dip of strata: 13°-17° (45° near the
border faults)
Lower Jurassic Rift
General Sequence of Formations
LOWER KAROO
Vúzi Formation (base – Upper Carboniferous)
Fluvial-glaciogenic characteristics
Basal conglomerates, sandstones, coally argillites and siltites.
Isolated patches, lowest depressions of Pre-Karoo landscape
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
André seam, w/ Matinde series
above, Moatize
2.2. KAROO IN TETE
Moatize Formation (Permian)
Occurrence of thick coal deposits (Nr seams 6-8).
Lays unconformably either on Precambrian rocks or on the Vúzi Formation.
Moatize area – 340 m
Other areas: from some to hundreds of meters
White to gray arkosic sandstones, micaceous sandstones with fossil flora of Glossopteris
and Gangamopteris, amongst others, and black argillites with coal seams.
Moatize – 6 seams
Mucanha-Vuzi – 6 seams
Thicknesses
Benga area – 4 seams(?)
Lateral extension
Great variation
Sanangoe – 8 seams
Matinde Formation
(Mid.-U. Permian)
White sandstones, sometimes arkosic and conglomeratic, with cross bedding.
In some areas, Matinde Fm. can present some coal seams.
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.2. KAROO IN TETE
LOWER-UPPER KAROO
Cádzi Formation
Transition from Lower-Upper Karoo - Permian/Triassic.
Composed of medium to coarse grained arkosic sandstones with cross-bedding, with
some limestones and carbonates sandstones
UPPER KAROO
Middle Triassic/Upper Jurassic
2 sedimentary formations, different types of sandstones.
Igneous Formations
Large scale cross-bedding
in Cádzi Formation
Basalts, rhyolites, andesites, etc.
Several igneous formations
Dolerite dykes which burn coal.
Zumbo Formation
Lualádzi Formation
Carumacáfuè Mountains consisting of
Zumbo Formation
Red dunes resulting from the
weathering of the Lualádzi sandstones
Great Dyke in Moatize River
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.2. KAROO IN TETE
1. MUCANHA-VÚZI AREA (Chicôa-Mecúcoè)
Several borehole programs: thickness of the Karoo
sequence in the Chicôa-Mecúcoè area, especially in
Mucanha-Vúzi sub-basin varies a lot.
Cross sections: half-graben structure evident,
Deepening of the basin to the west and to the south,
as a consequence of the complicated faulting affecting
this basin _ Seams dipping southwards and
westwards.
S
N
W
E
6 Coal zones named M1-M6 (CPRM, 1983) or B0-B5
(Lächelt, 2004)
SW
NE
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.2. KAROO IN TETE
2. SANÂNGOÈ AREA
NW-SE oriented syncline, SE plunging and obliterated by a border fault,
Precambrian rocks to the North.
Coal outcrops are well visible.
Dolerite dykes and sills (have little influence on coal).
Basin cut by faults perpendicular to the synclinal axis
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.2. KAROO IN TETE
3. MOATIZE AREA
VALE CONCESSION
(Moatize)
RIO TINTO CONCESSION
(Benga)
Chipanga Seam - Moatize River
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.2. KAROO IN TETE
3. MOATIZE AREA
Basin divided into several sections defined either by natural boundaries or tectonic structures
Graben oriented NW-SE and limiting faults, the biggest being Border Fault
Sediments somewhat folded, with anticline and syncline axes with a prevalent NW-SE direction
Several faults cut the basin, provoking vertical throws reaching 100 m.
Doleritic dykes (“Great
Dyke” cuts the NW part
of the basin).
Outcrops of several coal
seams:
Great
Dyke
1. Sousa Pinto
2. Chipanga
3. Bananeiras
4. Intermédia
5. Grande Falésia
6. André
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.2. KAROO IN TETE
3. MOATIZE AREA
VALE (2009)
Lachelt (2004)
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2.3. COAL-BEARING FORMATION
Metangula
~100 m
Moatize
~340 m
Sanângoè
~200 m
230-300 m
Mucanha-Vúzi
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3. PROPERTIES OF MOZAMBICAN COALS
In general, the Mozambican Permian coals are:
Bituminous, with rank varying from high to low volatile bituminous coals, occasionally
anthracitic
Richer in Vitrinite than in Inertinite,
Very low Liptinite content,
In general ash yield is high,
Minerals are finely intergrown with the organic matrix, thereby posing difficulties in
liberation during beneficiation
3.1. PETROGRAPHY
Dominance of vitrinite;
Moatize with somewhat more inertinitic coals;
Low content of liptinite (Mucanha-Vúzi) or almost absence (Moatize-Minjova-Mutarara).
References to the petrography of coals from other regions were found only for Metangula coals:
Mineral-rich (28% - 48%);
Vitrinite varying from 36% to 51%;
Liptinite in the range 1.9% to 2.5%.
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3.1. PETROGRAPHY
Fluorescence of Moatize coals
Fusinite with clay
minerals
Left: natural light; right: blue light. All: 600 x
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3.1. PETROGRAPHY
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3.2. RANK
Moatize: increase in rank with depth: from 1,28% in Grande Falésia (Bituminous B) to 1,51% in S. Pinto (bituminous A).
Minjova: %VR ranging between 1,36-1,43% - MVB (or bituminous B) to these coals
Mucanha-Vúzi: lower rank than Moatize, %VR that varies between 1,00-1,10%, approximate border between HVB-MVB
(bituminous B).
Benga are MVB (bituminous B).
%VR(max) varies from 1,16% in Top Chipanga Seam to 1,27-1,29% in Middle Chipanga and 1,27-1,37 in Bottom Chipanga,
i.e., increases with depth.
Mutarara: Rr between 1,93-3,86%, showing an anthracitic stage, some coal in LVB (many dolerite intrusions)
No information was found concerning reflectance of coals from the Metangula Basin. Reports refer to Bituminous C-D
Moatize
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
H2O
(%, ad)
Ash
(%, ad)
Volatile
Matter
(%, ad)
1,8-2,6
31,6-85,2
n.d.
14,78-26,48 0,30-3,50
Mucangádzi R. range of 27 samples (trench)
5,9-11,5
16,4-45,1
19,7-28,4
14.61-23.91 0.49-3.90
Vúzi R.
range of 28 samples (trench)
2,4-15,9
9,4-34,8
24,0-33,0
16.08-29.64 0.58-2.66
range of 36 samples (trench)
Chicôa- Bohozi R.
Mecúcoè Massínduè R. range of 18 samples (trench)
1,3-14,2
12,7-35,2
21,0-28,6
11.26-29.35 0.77-5.93
2,7-16,0
11,0-30,8
21,3-28,0
13.36-25.50 0.47-1.29
Basin
3.3.
PROXIMATE
ANALYSIS,
CALORIF IC
VALUE & TOTAL
SULFUR
Locality
Metangula unknown
Less – ChicoaMecucoe
Max – Metangula
& Mutarara
Sulfur – Varies
significantly;
Higher:
Metangula,
Mucangadzi,
Bohozi and some
Moatize coals
range of 27 samples
GCV
(MJ/kg, ad)
Sulfur
(%, ad)
Mucanha R.
range of 5 samples (trench)
1,0-1,8
13,8-33,0
19,5-26,1
21.77-30.60 0.74-1.82
Luângua R.
range of 56 samples (trench)
0,8-11,2
13,8-37,7
14,9-28,2
16.04-30.44 0.42-2.88
Zone 8 (drilling)
4,2
52,9
14,9
13,25
1,06
Zone 7 (drilling)
Zone 6 Upper (drilling)
4,0
3,7
42,5
35,1
21,9
25,1
17,30
20,28
1,24
1,06
Zone 6 Lower (drilling)
3,2
41,6
23,5
18,25
1,23
Zone 5 (drilling)
3,2
45,7
21,5
16,16
1,01
Zone 4 Upper (drilling)
3,9
34,5
25,6
22,07
1,25
Zone 4 Lower (drilling)
2,6
48,6
21,7
17,30
1,28
Chipanga/Chi. 3 Mine (undg./chan.)
0,9
13,7
17,2
29,98
0,74
Chipanga/Chi. 8 Mine (undg./chan.)
0,6
17,6
17,1
29,66
0,50
Sousa Pinto (avg., drilling)
0,84
56,07
12,15
13,80
1,10
Chipanga L. (avg., drilling)
0,83
32,86
16,92
19,31
4,42
0,85
42,84
15,51
15,83
3,83
0,87
38,11
16,38
17,73
4,11
0,92
38,09
16,74
17,57
4,03
1,04
41,76
16,30
16,45
3,77
Grande Falésia (avg., drilling)
1,04
43,74
16,75
15,62
3,80
André (avg., drilling)
1,20
36,18
18,68
21,37
3,81
RAW Coal
Ash – generally
high;
Sample
Sanângoè License 871L
Moatize
Section 6
Chipanga M. (avg., drilling)
Moatize- Moatize
Chipanga U. (avg., drilling)
Mutarara- Central Section
Bananeiras U. (avg., drilling)
N’condézi
Intermédia (avg., drilling)
Mutarara
Boreholes (range 171 samples)
0,2-1,4
33,5-89,8
4,1-35,5
2,78-22,8
0,03-2,53
Ncondédzi
Potential exp. thermal products
+8 (ar)
+22
n.a.
+25.12 (ar)
+1
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3.3. PROXIMATE ANALYSIS, CALORIF IC VALUE & TOTAL SULFUR
QUALITY OF SIZED FRACTIONS AND WASHED PRODUCTS
Comparisons not always possible given the different sampling techniques and objectives of each investigation.
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3.3. PROXIMATE ANALYSIS, CALORIF IC VALUE & TOTAL SULFUR
QUALITY OF SIZED FRACTIONS AND WASHED PRODUCTS
MINJOVA – sized fractions
Parameter
(air dry)
Parameters
(air dry)
ROM 20 x 5 ROM 10 x 0,5 ROM 5 x 0,5
ROM -0,5
Moisture, %
1,3
1,3
1,2
1,5
Ash, %
27,2
18,5
23.4
16,7
Volatiles, %
18,5
20,5
18,9
20,6
Fixed Carbon, %
53
59,7
56,5
61,2
Gross CV, MJ/kg
n.a.
n.a.
n.a.
n.a.
Total Sulfur, %
n.a.
n.a.
n.a.
n.a.
METANGULA
Parameter
Moisture, %
Ash, % (air dry)
Volatiles, % (air
dry)
Gross CV, MJ/kg
Sulfur, %
Ministry of
Geology, 1981
Washed (19
samples)
Wash Yield
(%)
Moisture (%)
Ash (%)
Volatiles (%)
Fixed
Carbon (%)
GCV (MJ/kg)
Total S (%)
Primary and Middlings Products for the
-25mm +10mm
-10mm+0.5mm fraction
fraction
Primary
Middlings
Primary
Middlings
product
product
product
product
composite of composite of
composite of composite of
all zones
all zones
all zones F1,40 all zones F1,60
F1,40
F1,60
29.7
36.3
12.8
30.6
5.6
8.9
32.3
3.6
36.4
24.6
4.4
17.5
31.6
3.7
31.3
26.6
53.2
35.4
46.5
38.4
30.03
1.31
19.86
1.20
26.91
1.25
21.8
1.18
BENGA
VPDM (2012)
Drill core samples of seams N3, N23,
N2, N12, N1C1, N1C2, N1C3, N1C4
(cut-off density not
known)
F 1.50
F 1.90
1,8 – 3,0
6,28-7,90
4,99-6,40
15,4 – 26,8
12,30-14,88
28,18-35,29
27,2 – 32,2
32,80-34,55
27,21-29,58
30,19 -33,20
25,46-26,50
18,25-21,28
1,30 – 1,40
1,20-2,72
0,98-3,99
SANÂNGOÈ
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
4. RESOURCES
Lack of reliable numbers that illustrate the real situation.
The Mining Directorate of Mozambique (DNM, 2013) compiled a table of coal resources(JORC) with the information
provided by the coal companies :
TOTAL of 25,439 million tonnes;
Inferred - 11,348 million tonnes;
Indicated - 10,496 million tonnes
Measured – 3,585 million tonnes
Numbers apply to 16 licenses:
10 from Moatize-NcondéziMutarara
2 from Sanângoè-Mefidézi
3 from Mucanha-Vuzi
1 from Metangula
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
6. CONCLUSIONS
Much work is still required, especially of scientific nature, and most especially in the remote areas such as western
Tete and Niassa Provinces to which access remains a challenge .
In general, Mozambican Permian coals are medium to low volatile bituminous, with some areas having high volatile
bituminous, and a few others reaching the anthracite stage.
Petrographically speaking, these coals are mainly vitrinitic.
Total sulfur content of sized and washed products typically around 1%, with some horizons having higher contents.
Almost all basins/sub-basins coals can be beneficiated to yield both coking coals and thermal coal fractions.
Resources and Reserves still do be evaluated with more studies and exploration works.