1. PRECAMBRIAN MANGANESE DEPOSITS: GEOLOGICAL SETTING, METALLOGENESIS AND PALEOENVIRONMENTAL IMPLICATIONS
NIC BEUKES AND JENS GUTZMER*
Paleoproterozoic Mineralization Research Group Department of Geology
University of Johannesburg
8 Department of Mineralogy, TU Bergakademie Freiberg, Freiberg, Germany.
UNESP, Brazil, 2011

2. PRECAMBRIAN MANGANESE DEPOSITS: GEOLOGICAL SETTING, METALLOGENESIS AND PALEOENVIRONMENTAL IMPLICATIONS
OUTLINE
PART 1; DISTRIBUTION, CLASSIFICATION, RESERVES, TEMPORAL VARIATIONS, CHEMICAL AND BIOGEOCHEMICAL CONTROLS ON DEPOSITION
PART 2: DEPOSITS PREDATING GOE
PART 3: DEPOSITS IMMEDIATELY POSTDATING GOE
PART4: MESOPROTEROZOIC DEPOSITS
PART 5; NEOPROTEROZOIC DEPOSITS AND CONCLUSION

3. Geographic Distribution of important deposits
Mangyshlak
Nikopol
Chiatura
Imini
Sinian
Sausar
Molango
Tambao
IOG
Goa
Nsuta
Serra do Navio
Moanda
Azul
Kisenge
Groote Eylandt
Urucum
Woodie Woodie
KMF
PMF
Manganese Deposits

4. MINERALOGICAL CLASSIFICATION
Mn-carbonate ± Mn-oxide
Kutnahorite Ca(Mn2+, Mg)(CO3) Rhodochrosite (Mn,Ca)CO3 Mn-calcite (Ca, Mn)CO3
Mn-oxide ± carbonate
Braunite Mn2+Mn3+6SiO12 Hausmannite Mn2+Mn3+2O Bixbyite Hematite Fe2O3
Supergene altered Mn4+ oxyhydroxide
Todorokite (Na, Ca)Mg2+Mn2+lMn4+6-lO12 * xH2O Manganomelane (K, Na, Ba)Mn4+8O16 * xH2O Pyrolusite Mn4+O2

5. Genetic subdivision of important Mn deposits
BIF-associated deposits
Kalahari Manganese Field
Rooinekke
Urucum, Otjosondu, Malyi Khingan
Shallow marine oolitic/oncolitic deposits
Nikopol, Bol’se Tokmak, Chiatura, Mangyshlak
Groote Eylandt
Bronkhorstfontein (Tolwe, South Africa)
Black shale-hosted deposits
Azul
Moanda, Nsuta, Tambao, Serro do Navio, Kisenge
Goa, Sausar, IOG, Sinian, Woodie-Woodie
Molango, Cambrian in China (Taojiang etc.)
Karst-associated deposits
Imini
Postmasburg manganese field, Woodie Woodie

6. Geographic Distribution of important deposits
Malyi Khingan
Mangyshlak
Nikopol
Chiatura
Sinian
Imini
Sausar
Molango
Tambao
IOG
Goa
Nsuta
Serra do Navio
Moanda
Azul
Kisenge
Groote Eylandt
Otjosondu
Urucum
Bronkhorstfontein
R-KMF
Woodie Woodie
PMF
Manganese Deposits

7. Total mineral resource: ca. 5 Gt
Temporal Distribution
Total mineral resource: ca. 5 Gt
Manganese Deposits

8. Global Mn ore production
Total production: ~ 12 Mt
Manganese Deposits

9. South Africa’s manganese wealth (resources)
The KMF:
~ 4billion tons of mineable resource
~ 80% of world’s resource
Mineral Reserve position of South Africa, 2003 (from DME 21st edition of South Africa’s Mineral Industry Report, 2004)
Manganese Deposits

10. SA manganese mining in global context
South Africa’s Role in World Mineral Production, 2003 (from DME 21st edition of South Africa’s Mineral Industry Report, 2004)
Manganese Deposits

11. Concentration of Mn in Precambrian vs Phanerozoic
Manganese Deposits

12. Mn in sediments - a tale of three oxidation states
Immobile
Mobile
Immobile
Manganese Deposits

13. Inorganic Precipitation of Mn-oxides
Experimental studies (Hem and Lind, 1983) showed:
Mn2+ is oxidized to either metastable Mn3+ oxyhydroxide (manganite) or mixed valency state mineral like hausmannite.
Manganite subsequently transforms to MnO2; hausmannite transforms to Mn2+ and MnO2
These steps limits rate of formation of MnO2
Reaction rates enhanced by Mn-oxidizing microbes
Manganese Deposits

14. Microbial Catalization of Mn-oxide Precipitation
Precipitation by Mn-oxidizing Chemolithoautotrophs
13Mn2+ + 6CO O2 + 19H2O = C6H12O6 + 13MnO2 + 26H+ (1)
12Mn2+ + 6CO2 + H2O = C6H12O6 + 12MnO2 + 24H+ (2)
Overall Reaction:
Mn2+ + 0,5O2 + H2O = MnO2 + 2H+
(0,5 autotrophy and 0,5 chemolithotrophy)
Manganese Deposits

15. Microbial catalization process
Bacteria first enzymatically oxidize Mn2+ to Mn3+
2Mn2+ + 0,5O2 + 2H+ = 2Mn3+ + H2O
This Mn3+ remains bound to manganese oxidizing enzyme
The same enzyme then catalyzes the oxidation of bound Mn3+ to MnO2 via reaction
2Mn3+ +0,5O2 + 3H2O = 2MnO2 + 6H+
These reactions not only accelerates transformation of Mn3+ to Mn4+ but also ensures that more Mn3+ is converted to MnO2 than the only about 50% in case of disproportionation of hausmannite
Manganese Deposits

16. Manganese Respiration

17. Manganese and Timing of Oxygenic Photosynthesis
GOE

19. Anoxygenic vs Oxygenic Photosynthesis
CO2 + 2H2S CH2O + 2S +H2O
Oxygenic
CO2 + 2H2O CH2O + O2
Sunlight
Sunlight
When did the latter develop?

20. Unlike iron no anaerobic oxidation of Mn known:
Mn oxidation implies presence of free oxygen

21. Microbial Catalization of Mn-oxide Precipitation
Mn oxidation requires free oxygen: Oxygen = oxygenic photosynthesis
Precipitation by Mn-oxidizing Chemolithoautotrophs
13Mn2+ + 6CO O2 + 19H2O = C6H12O6 + 13MnO2 + 26H+ (1)
12Mn2+ + 6CO2 + H2O = C6H12O6 + 12MnO2 + 24H+ (2)
Overall Reaction:
Mn2+ + 0,5O2 + H2O = MnO2 + 2H+
(0,5 autotrophy and 0,5 chemolithotrophy)
Manganese Deposits

22. Precambrian Mn Deposits
Temporal Litho- and Chemofacies Distribution
Manganese Deposits

23. GOE
Manganese Deposits