Lopo VasconcelosDept. Geology
Eduardo Mondlane UniversityMaputo, Mozambique
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 topmostUpper 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 existTete 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 basementfollowed by bimodal igneous formations of Lower Jurassic ageand/or unconformably overlain by Middle Jurassic or youngerstrata.
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
Bimodal Igneous formations
2. GEOLOGY OF THE MAIN MOZAMBICAN COAL (KAROO) BASINS
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SEDIMENTARY IGNEOUS
Karoo basins geodynamically subdivided into (Hobday 1986 in Cairncross 1989):
Foredeep basins
Intracratonic sag basins
Rifts
In general:
sediments of glaciogenic//temperate and deltaic origin
fluvial/lacustrine clastic sediments(COAL)
more arid and warm conditions
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2. GEOLOGY OF THE MAIN MOZAMBICAN KAROO BASINS
Mozambique: Grabens/Half-grabens
Zambezi Valley: divided into W and E areas, separated by Precambrian rocks in Songo area.
Western: E-W trend;
Eastern: NW-SE trend;
Each of these areas: subdivided into structurally controlled smaller sub-basins.
Three main basins:
correspond to the Zambezi Mobile Belt between the Zimbabwe & Congo Cratons.
Chicôa-Mecúcoè
Sanângoè-Mefídezi
Moatize-Minjova (NW and SE extensions to Nkondezi and Mutarara)
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
2. GEOLOGY OF THE MAIN MOZAMBICAN KAROO BASINS
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 thickUpper Karoo up to 6 km thick
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
K2 local basal conglomerates, coarse grained gritty sandstones, siltstones, mudstones and thin coal beds.
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
Lower
Upper
ÿ1-4 m thickÿcoal seams 110-272 cm thick
ÿ1-4 m thickÿcoal seams 67-100 cm thick
343
m
Ecca: - subdivided into 3 horizons: K2, K3 and K4.
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%)
Sterile16.4 m
Coal 14.4m
15%
Border faults parallel to Zambezi Mobile Belt
Faults filled with dolerite dykes (igneousepisode
Dip of strata: 13°-17° (45° near the border faults)
2.2. KAROO IN TETE
Lower Jurassic Rift
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Fluvial-glaciogenic characteristics
Basal conglomerates, sandstones, coally argillites and siltites.
Isolated patches, lowest depressions of Pre-Karoo landscape
General Sequence of Formations
Vúzi Formation (base – Upper Carboniferous)
LOWER KAROO
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
Benga area – 4 seams(?)
Sanangoe – 8 seams
André seam, w/ Matinde series above, Moatize
White sandstones, sometimes arkosic and conglomeratic, with cross bedding.
In some areas, Matinde Fm. can present some coal seams.
Matinde Formation (Mid.-U. Permian)
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2.2. KAROO IN TETE
Thicknesses
Lateral extensionGreat variation
Transition from Lower-Upper Karoo - Permian/Triassic.
Composed of medium to coarse grained arkosic sandstones with cross-bedding, with some limestones and carbonates sandstones
Cádzi Formation
Large scale cross-beddingin Cádzi Formation
LOWER-UPPER KAROO
Middle Triassic/Upper Jurassic
2 sedimentary formations, different types of sandstones.
Several igneous formations
UPPER KAROO
Zumbo Formation
Carumacáfuè Mountains consisting ofZumbo Formation
Lualádzi Formation
Red dunes resulting from the weathering of the Lualádzi sandstones
Igneous FormationsBasalts, rhyolites, andesites, etc.Dolerite dykes which burn coal.
Great Dyke in Moatize River
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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.
6 Coal zones named M1-M6 (CPRM, 1983) or B0-B5 (Lächelt, 2004)
S N
W
SW
E
NE
2.2. KAROO IN TETE
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
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
2. SANÂNGOÈ AREA
NW-SE oriented syncline, SE plunging2.2. KAROO IN TETE
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VALE CONCESSION(Moatize)
RIO TINTO CONCESSION(Benga)
3. MOATIZE AREA
2.2. KAROO IN TETE
Chipanga Seam - Moatize River
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GreatDyke
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.
3. MOATIZE AREA
2.2. KAROO IN TETE
Doleritic dykes (“Great Dyke” cuts the NW part of the basin).
Outcrops of several coal seams:
1. Sousa Pinto
2.Chipanga3. Bananeiras
4. Intermédia
5. Grande Falésia
6. André
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3. MOATIZE AREA
2.2. KAROO IN TETE
Lachelt (2004)
VALE (2009)
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2.3. COAL-BEARING FORMATION
Metangula
230-
300
m
Mucanha-Vúzi Sanângoè Moatize
~340
m
~200
m
~100
m
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. PETROGRAPHYDominance 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
Left: natural light; right: blue light. All: 600 x
Fusinite with clay minerals
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
3.1. PETROGRAPHY
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
Moatize
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
3.2. RANK
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa
Mozambique Coal Conference, 02.10.2013, Johannesburg, South AfricaBasin Locality Sample H2O(%, ad)
Ash(%, ad)
VolatileMatter(%, ad)
GCV(MJ/kg, ad)
Sulfur(%, ad)
Metangula unknown range of 27 samples 1,8-2,6 31,6-85,2 n.d. 14,78-26,48 0,30-3,50
Chicôa-Mecúcoè
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
Bohozi R. range of 36 samples (trench) 1,3-14,2 12,7-35,2 21,0-28,6 11.26-29.35 0.77-5.93
Massínduè R. range of 18 samples (trench) 2,7-16,0 11,0-30,8 21,3-28,0 13.36-25.50 0.47-1.29
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
Sanângoè License 871L
Zone 8 (drilling) 4,2 52,9 14,9 13,25 1,06Zone 7 (drilling) 4,0 42,5 21,9 17,30 1,24Zone 6 Upper (drilling) 3,7 35,1 25,1 20,28 1,06Zone 6 Lower (drilling) 3,2 41,6 23,5 18,25 1,23Zone 5 (drilling) 3,2 45,7 21,5 16,16 1,01Zone 4 Upper (drilling) 3,9 34,5 25,6 22,07 1,25Zone 4 Lower (drilling) 2,6 48,6 21,7 17,30 1,28
Moatize-Mutarara-N’condézi
MoatizeSection 6
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
MoatizeCentral Section
Sousa Pinto (avg., drilling) 0,84 56,07 12,15 13,80 1,10Chipanga L. (avg., drilling) 0,83 32,86 16,92 19,31 4,42Chipanga M. (avg., drilling) 0,85 42,84 15,51 15,83 3,83Chipanga U. (avg., drilling) 0,87 38,11 16,38 17,73 4,11Bananeiras U. (avg., drilling) 0,92 38,09 16,74 17,57 4,03Intermédia (avg., drilling) 1,04 41,76 16,30 16,45 3,77Grande Falésia (avg., drilling) 1,04 43,74 16,75 15,62 3,80André (avg., drilling) 1,20 36,18 18,68 21,37 3,81
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
3.3. PROXIMATE ANALYSIS, CALORIF IC VALUE & TOTAL SULFUR
Ash – generally high;
Less – Chicoa-Mecucoe
Max – Metangula& Mutarara
Sulfur – Varies significantly;
Higher: Metangula, Mucangadzi, Bohozi and some Moatize coals
RAW Coal
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
MINJOVA – sized fractionsParameter
(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 1,5Ash, % 27,2 18,5 23.4 16,7Volatiles, % 18,5 20,5 18,9 20,6Fixed Carbon, % 53 59,7 56,5 61,2Gross CV, MJ/kg n.a. n.a. n.a. n.a.Total Sulfur, % n.a. n.a. n.a. n.a.
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3.3. PROXIMATE ANALYSIS, CALORIF IC VALUE & TOTAL SULFURQUALITY OF SIZED FRACTIONS AND WASHED PRODUCTS
METANGULA
Parameter
Ministry of Geology, 1981 VPDM (2012)
Washed (19 samples)
(cut-off density not known)
Drill core samples of seams N3, N23, N2, N12, N1C1, N1C2, N1C3, N1C4
F 1.50 F 1.90
Moisture, % 1,8 – 3,0 6,28-7,90 4,99-6,40Ash, % (air dry) 15,4 – 26,8 12,30-14,88 28,18-35,29Volatiles, % (air dry) 27,2 – 32,2 32,80-34,55 27,21-29,58
Gross CV, MJ/kg 30,19 -33,20 25,46-26,50 18,25-21,28Sulfur, % 1,30 – 1,40 1,20-2,72 0,98-3,99
SANÂNGOÈ
Parameters(air dry)
Primary and Middlings Products for the
-10mm+0.5mm fraction -25mm +10mm fractionPrimary product
composite of all zones F1,40
Middlingsproduct
composite of all zones F1,60
Primary product
composite of all zones
F1,40
Middlingsproduct
composite of all zones
F1,60Wash Yield (%) 29.7 36.3 12.8 30.6
Moisture (%) 5.6 3.6 4.4 3.7Ash (%) 8.9 36.4 17.5 31.3Volatiles (%) 32.3 24.6 31.6 26.6Fixed Carbon (%) 53.2 35.4 46.5 38.4
GCV (MJ/kg) 30.03 19.86 26.91 21.8Total S (%) 1.31 1.20 1.25 1.18
BENGA
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-Ncondézi-Mutarara
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.
Mozambique Coal Conference, 02.10.2013, Johannesburg, South Africa