2. lopo vasconcelos - fossil fuellopo vasconcelos dept. geology eduardo mondlane university maputo,...

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.


Bimodal Igneous formations

2. GEOLOGY OF THE MAIN MOZAMBICAN COAL (KAROO) BASINS


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: 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)



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


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.


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


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)


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


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


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


VALE CONCESSION(Moatize)

RIO TINTO CONCESSION(Benga)

3. MOATIZE AREA

2.2. KAROO IN TETE

Chipanga Seam - Moatize River


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


3. MOATIZE AREA

2.2. KAROO IN TETE

Lachelt (2004)

VALE (2009)


2.3. COAL-BEARING FORMATION

Metangula

230-

300

m

Mucanha-Vúzi Sanângoè Moatize

~340

m

~200

m

~100

m


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%.


3.1. PETROGRAPHY

Fluorescence of Moatize coals

Left: natural light; right: blue light. All: 600 x

Fusinite with clay minerals


3.1. PETROGRAPHY


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 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.


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.


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


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.


2. lopo vasconcelos - fossil fuellopo vasconcelos dept. geology eduardo mondlane university maputo,...

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