Potential of Tin and tantalum/niobium in Rondônia, Brazil and the optimization of the processing methods

Transcription

1 Potential of Tin and tantalum/niobium in Rondônia, Brazil and the optimization of the processing methods German-Brazilian Mining and Raw Materials Conference Nova Lima, 21 st June 2018 Dr. Herwig Marbler (BGR-DERA) Tiago Buch (CPRM) Dr. Simon Goldmann (BGR-DERA) 1

2 BGR-CPRM cooperation project according to a 5 years agreement (MoU), signed in Oct Rondônia tin ores and their potential of Sn, Ta/Nb Aim of the project: Mineralogical and geochemical characterization of the Sn and Ta/Nb mineralizations Optimization of the gravimetric, magnetic (and chemical) separation of cassiterite, columbite and other economically important minerals Enhancement of the recovery of Sn and Ta/Nb 2

3 Agenda Introduction on the Rondônia Tin Province and economic background Geological, mineralogical and geochemical characteristics of the primary (hard rocks), secondary (alluvium and tailings) ores Used processing techniques and challenges Preliminary results of processing test works: density separation, magnetic separation, identification of radioactive minerals Summary 3

4 The Amazonian Craton and its mineral provinces Mineral provinces: CMP: Carajás Mineral Province Manaus TP: Transamazonian Province AFGP: Alta Floresta Gold Province TMP: PTP: RTP: Tapajós Mineral Province Pitinga Tin Province Rondônia Tin Province Bettencourt et al

5 The Rondônia tin province Bettencourt et al

6 US$ / tonne Tonne Tin market: development of tin prices vs. warehouse stocks 22,000 21,000 tin price: LME, min % Sn 14,000 12,000 20,000 10,000 19,000 18,000 8,000 6,000 4,000 17,000 2,000 16,000 0 SHFE Stocks LME Stocks LME Tin Price [US$/t] source: BGR 2018; Asian Metalls

7 Tin production (metric tonnes) World tin production 390,000 Refined tin production 2017: 370,300 t* % China % Indonesia % Malaysia % Perú % Bolivia % Brazil (14,500 t) Mine production 2017: 290,000 t** % China % Indonesia % Myanmar % Bolivia % Perú - 4,8 % Brazil (13,900 t) 370, , , ,000 Rondônian mine production (2017): 6,616 t Sn** in concentrate (45-50 % Sn) 290, , , refined mining prod. source: BGR 2018, *Metal Market Mag., **USGS 2018, ***ANM

8 US$/kg Tantalum price development 220 World tantalum production (2016): 1730 t (1582 t mining t from tin slags) % Great Lake Region (Ruanda, DR Congo) % Brazil (208 t) % China Concentrate, 30 % Ta 2 O 5, cif China CIF Cost, Insurance, Freight source: BGR

9 CPRM-BGR Rondônia Sn-Ta project BF MS SB CA Four mines and garimpos (cooperatives) nearby the city of Ariquemes were chosen for investigations and further processing testworks: Massangana (CEMAL cooperative) - MS Bom Futuro (COOPERSANTA cooperative, Meridien Mining Ltd.) - BF Cachoeirinha (Metalmig Ltda.) - CA Santa Bárbara (Estanho de Rondônia SA ERSA-CSN) - SB 9

10 Bom Futuro (Cooper Santa) Mining and processing of alluvium und tailings as well as ~10 % primary ore Reserves + resources: % Sn (up to >1% Sn) + 15,000 t Sn in primary ore Production: approx. 10 t cassiterite conc./day (1,775 t Sn in 2016) 10

11 Bom Futuro primary ore (pegmatites and greisens) 11

12 Sampling of placer and tailings 12

13 Conventional processing method for cassiterite and columbite concentrates Gravimetric and magnetic separation of the cassiterite ore are traditionally used sampling crushed prim. ore Mobile jiggs used by the garimpeiros for secondary ore (placers and tailings) in the mining areas (MS, CA) Crushing of primary ore in BF sampling Sieving Sieving of the ore and the preconcentrate is carried out only in SB and BF Processing plant: spiral separators (BF, SB), shaking tables and magnetic separation to produce the final concentrates 13

14 Conventional processing method for cassiterite and columbite concentrates mobile jiggs, MS 14

15 Conventional processing method for cassiterite and columbite concentrates spiral separator; SB 15

16 Conventional processing method for cassiterite and columbite concentrates shaking tables and magnetic separator (MS, BF) 16

17 Development of advanced processing methods Gravimetric and magnetic separation on pre-concentrates and placer/tailings Different grain size fractions (GSF) are devided into weight fractions (4x) with optical determination as well as MLA analytics benchmark experiments with high density liquids for density separation Magnetic separation into three fractions: ferro-, dia- and paramagnetic minerals Processing tests are carried out at GEOS Ingenieur-Gesellschaft mbh Freiberg; analytical works at BGR and GEOS 17

18 Development of advanced processing methods Shaking table: Separation of minerals as a function of different grain fractions Fraction µm: Sharp separation of heavy fractions (SM1 and SM2), middlings (MD) and light fraction (LF) almost free of heavy minerals Fraction µm: Sharp separation of SM1, parts of the heavy fraction still in SM2, MD and LF almost free of heavy minerals Fraction µm: No clear separation of the heavy minerals in SM1, parts of the heavy fraction still in SM2, MD and LF almost free of heavy minerals Fraction µm: Barely visible separation of heavy minerals - no heavy minerals present or too strong intergrowths? 18

19 Development of advanced processing methods Liberation of ore minerals: Initial indications for mineral intergrowth are shown by MLA. Intergrowth of ore minerals are visible in particular within the coarse fractions. content: ~ 16 % cassiterite content: ~ 54 % cassiterite 19

20 Development of advanced processing methods Optical assessments: mineral intergrowth and coatings on polished sections Kl Cs Col Gt Cs 100 µm 100 µm Intergrowth of cassiterite (Cs) and Mn-columbite (Col); goethite (Gt), kaoline (Kl) 20

21 Development of advanced processing methods Results from density separation: percentage shares of valuable elements (mass %) per size fraction: Size Mass P 2 O 5 TiO 2 Fe 2 O 3 Zr Nb Sn Ce Ta Th U [µm] [%] percent Sum of fractions Grain size fraction µm contains more than 91% of valuable elements Sn, Nb, Ta - Decrease of Th and reject of Monazite by grain size regulation and magnetic separation - Zircon contains most of Uranium; U decreases with separation of the fraction >500 µm 21

22 Development of advanced processing methods Separation of radioactive minerals: zircon, monazite, xenotime and euxenite Magnetic separation of ferro- para- and dia-magentic mineral fractions zircon monazite density (g/cm³): quartz, feldspar ( ) < xenotime (4.3) < zircon (4.7) < monazite (5.2) columbite (5.4) < cassiterite (7.2) magnetic properties: ferro (magnetite, ilmenite, etc.), para: (monazite, columbite), dia: (cassiterite, xenotime) 22

23 Development of advanced processing methods Radioactive minerals Mon Cs Rt Cs Mon Eux Ilm 200 µm 500 µm REE phosphate monazite (Mon) and euxenite (Eux) Ilm: ilmenite; Rt: rutile; Cs: cassiterite 23

24 Development of advanced processing methods Magnetic separation a) Belt magnetic separator: Separation para-diamagnetic materials at 1.1 Tesla (big output but poor direct adjustment) b) Frantz magnetic separator: para-diamagnetic materials/minerals (accurate adjustment, low output of material) c) Ferro magnetic separator: Separation ferromagnetic materials (0.1 Tesla) (low proportion of ferromagnetic minerals) 24

25 Development of advanced processing methods Separation of MS sample: µm, SM1, Para1 stepwise on Frantz-Magnetic-Separator: radiation element content mineral content Ferro to strongly paramagnetic: Ilmenite, (Magnetite) Medium paramagnetic: Columbite, (Monazite) Medium to low paramagnetic: Monazite, Xenotime Low paramagnetic to diamagnetic: Fe-rich Cassiterite and Cassiterite 25

26 Summary and conclusions Great potential of tin (and niobium/tantalum) in the Rondônian Tin Province Recovery of cassiterite (columbite) with current methods/techniques could be optimized (and separation of monazite, zircon, xenotime) Mineralogical (and geochemical) investigations as well as investments in processing techniques are required Mineralogical results reveal that the grain size (>90% of valuable minerals within µm fraction), mineral intergrowth (>1000µm) and slight differences magnetic properties are critical factors for the ore processing At least three radioactive minerals are identified; the radioactivity of some of the ore concentrates (and slags) is often too high for the transport (shipping) 26

27 Thank you for your attention! CETEM (RJ) 27