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

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Presentation on theme: "PRECAMBRIAN MANGANESE DEPOSITS: GEOLOGICAL SETTING, METALLOGENESIS AND PALEOENVIRONMENTAL IMPLICATIONS NIC BEUKES AND JENS GUTZMER * Paleoproterozoic Mineralization."— Presentation transcript:

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

4 4 MINERALOGICAL CLASSIFICATION Mn-carbonate ± Mn-oxide Kutnahorite Ca(Mn 2+, Mg)(CO 3 ) 2 Rhodochrosite (Mn,Ca)CO 3 Mn-calcite(Ca, Mn)CO 3 Mn-oxide ± carbonate BrauniteMn 2+ Mn 3+ 6 SiO 12 HausmanniteMn 2+ Mn 3+ 2 O 4 Bixbyite HematiteFe 2 O 3 Supergene altered Mn 4+ oxyhydroxide Todorokite(Na, Ca)Mg 2+ Mn 2+ l Mn 4+ 6-l O 12 * xH 2 O Manganomelane (K, Na, Ba)Mn 4+ 8 O 16 * xH 2 O Pyrolusite Mn 4+ O 2

5 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, Bolse 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

6 Manganese Deposits6 Geographic Distribution of important deposits R-KMF PMF Urucum Azul Serra do Navio Imini Molango Nsuta Tambao Kisenge Moanda Goa IOG Sausar Chiatura Nikopol Mangyshlak Groote Eylandt Sinian Malyi Khinga n Otjosondu Woodie

7 Manganese Deposits7 Temporal Distribution Total mineral resource: ca. 5 Gt

8 Manganese Deposits8 Global Mn ore production Total production: ~ 12 Mt

9 Manganese Deposits9 South Africas manganese wealth (resources) The KMF: ~ 4billion tons of mineable resource ~ 80% of worlds resource

10 Manganese Deposits10 SA manganese mining in global context

11 Concentration of Mn in Precambrian vs Phanerozoic Manganese Deposits11

12 Manganese Deposits12 Mn in sediments - a tale of three oxidation states Mobile Immobile

13 Inorganic Precipitation of Mn-oxides Manganese Deposits13

14 Microbial Catalization of Mn-oxide Precipitation Manganese Deposits14

15 Microbial catalization process Bacteria first enzymatically oxidize Mn 2+ to Mn 3+ 2Mn 2+ + 0,5O 2 + 2H + = 2Mn 3+ + H 2 O This Mn 3+ remains bound to manganese oxidizing enzyme The same enzyme then catalyzes the oxidation of bound Mn 3+ to MnO 2 via reaction 2Mn 3+ +0,5O 2 + 3H 2 O = 2MnO 2 + 6H + These reactions not only accelerates transformation of Mn 3+ to Mn 4+ but also ensures that more Mn 3+ is converted to MnO 2 than the only about 50% in case of disproportionation of hausmannite Manganese Deposits15

16 Manganese Respiration

17 Manganese and Timing of Oxygenic Photosynthesis GOE

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19 Anoxygenic vs Oxygenic Photosynthesis Anoxygenic CO 2 + 2H 2 S CH 2 O + 2S +H 2 O Oxygenic CO 2 + 2H 2 O CH 2 O + O 2 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 Manganese Deposits21 Mn oxidation requires free oxygen: Oxygen = oxygenic photosynthesis

22 Manganese Deposits22 Precambrian Mn Deposits Temporal Litho- and Chemofacies Distribution

23 Manganese Deposits23 GOE


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