PRECAMBRIAN MANGANESE DEPOSITS: GEOLOGICAL SETTING, METALLOGENESIS AND PALEOENVIRONMENTAL IMPLICATIONS NIC BEUKES AND JENS GUTZMER * Paleoproterozoic Mineralization.

PRECAMBRIAN MANGANESE DEPOSITS: GEOLOGICAL SETTING,

METALLOGENESIS AND PALEOENVIRONMENTAL

IMPLICATIONS

NIC BEUKES AND JENS GUTZMER*

Paleoproterozoic Mineralization Research GroupDepartment of GeologyUniversity of Johannesburg

8 Department of Mineralogy, TU Bergakademie Freiberg, Freiberg, Germany.

UNESP, Brazil, 2011

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

Manganese Deposits 3

Geographic Distribution of important deposits

KMF

PMF

Urucum

Azul

Serra do Navio

Imini

Molango

Nsuta

Tambao

KisengeMoanda

Goa

IOGSausar

Chiatura

NikopolMangyshlak

Groote Eylandt

Sinian

Woodie Woodie

4

MINERALOGICAL CLASSIFICATION

• Mn-carbonate ± Mn-oxide

Kutnahorite Ca(Mn2+, Mg)(CO3)2 Rhodochrosite

(Mn,Ca)CO3

Mn-calcite (Ca, Mn)CO3

• Mn-oxide ± carbonate

Braunite Mn2+Mn3+6SiO12

Hausmannite Mn2+Mn3+2O4

Bixbyite

HematiteFe2O3

• 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

1. BIF-associated deposits

• Kalahari Manganese Field

• Rooinekke

• Urucum, Otjosondu, Malyi Khingan

2. Shallow marine oolitic/oncolitic deposits

• Nikopol, Bol’se Tokmak, Chiatura, Mangyshlak

• Groote Eylandt

• Bronkhorstfontein (Tolwe, South Africa)

3. Black shale-hosted deposits

• Azul

• Moanda, Nsuta, Tambao, Serro do Navio, Kisenge

• Goa, Sausar, IOG, Sinian, Woodie-Woodie

• Molango, Cambrian in China (Taojiang etc.)

4. Karst-associated deposits

• Imini

• Postmasburg manganese field, Woodie Woodie

Manganese Deposits 6

Geographic Distribution of important deposits

R-KMF

PMF

Urucum

Azul

Serra do Navio

Imini

Molango

Nsuta

Tambao

KisengeMoanda

Goa

IOGSausar

Chiatura

NikopolMangyshlak

Groote Eylandt

Sinian

Malyi Khingan

Otjosondu

Woodie Woodie

Manganese Deposits 7

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

Manganese Deposits 10

SA manganese mining in global context

Concentration of Mn in Precambrian vs Phanerozoic

Manganese Deposits 11

Manganese Deposits 12

Mn in sediments - a tale of three oxidation states

Mobile

Immobile

Immobile

Inorganic Precipitation of Mn-oxides

Manganese Deposits 13

Microbial Catalization of Mn-oxide Precipitation

Manganese Deposits 14

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 15

Manganese Respiration

Manganese and Timing of Oxygenic Photosynthesis

GOE

Anoxygenic vs Oxygenic Photosynthesis

• Anoxygenic

CO2 + 2H2S CH2O + 2S +H2O

• Oxygenic

CO2 + 2H2O CH2O + O2

Sunlight

Sunlight

When did the latter develop?

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

Microbial Catalization of Mn-oxide Precipitation

Manganese Deposits 21

Mn oxidation requires free oxygen: Oxygen = oxygenic photosynthesis

Manganese Deposits 22

Precambrian Mn Deposits

Temporal Litho- and Chemofacies Distribution

Manganese Deposits 23

GOE