PRESENTATION ON MANGANESE ORE DEPOSITS OF SMIORE FOR THE WORK SHOP ON REVISION OF THRESHOLD VALUES OF MINERALS AT GOA

Transcription

1 PRESENTATION ON MANGANESE ORE DEPOSITS OF SMIORE FOR THE WORK SHOP ON REVISION OF THRESHOLD VALUES OF MINERALS AT GOA

2 INTRODUCTION The Sandur Manganese & Iron Ores Ltd. (SMIORE) are operating Two leases ML 2678 & 2679 over an area of 2,000 hectares (1750 Ha Forest and 250 Ha Revenue) in Ramanadurg & Swamimalai Blocks, Sandur Taluk, Ballari District, Karnataka State. Mining operations in the area are going on since 1907 (110 years ). SMIORE is operating the mines from 1954 (63 years). Total employs as on date is about As per CEC, both the leases of SMIORE are in Category A. The permitted production limits are 1.60 MTPA of Iron Ore and MTPA of Manganese ore. Manganese Ore occurs in pockets and pods with a size range of few metres to about 40 metres. Mining requires huge excavations of over- burden. Average ratio of ore to over-burden is 1:25. There are 14 active and 26 inactive pits. 2

3 LOCATION Manganese ore deposits of the area are a part of Late Archaean Sandur schist belt in the Dharwar craton of South India (Long E; Lat N). The Sandur schist belt consists of Eastern and Western meta-sedimentary belts and a central meta-volcanic belt. GOOGLE IMAGES SHOWING LOCATION OF STUDY AREA SANDUR SCHIST BELT 3

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5 Geology and Occurrence: The Manganese ore deposits are limited to the western meta-sedimentary belt. Manganese Ore occurs as discrete lenticular bodies (pockets, pods and lenses) of varying magnitude in mangano-phyllite host rock, otherwise called as ore zone. General strike direction of ore zones is NNW-SSE and average dip angle is about 50 O due NNE. Lateritization and weathering have played an important role in the enrichment of the Manganese in ore zones. Some ore pockets are formed by the process of residual concentration and some by supergene enrichment. Manganese ore is an in-homogeneous mixture of Pyrolusite, Psilomelane, Cryptomelane, and ferruginous minerals like Limonite, Goethite, Hematite, and shows a wide range of variation from high ferruginous ore to low ferruginous types. In general, the thickness of ore bodies ranges from few centimeters to about 10m whereas length ranges from few meters to about 40m. The Manganese metal content in ore bodies is not homogeneous. Lot of interstitial waste is found in between concentrated Manganese portions. 5

6 TYPICAL CROSS-SECTION THROUGH A MANGENESE ORE PIT 6

7 EARLY EXPLORATION The pioneers like Brucefoot, & B.Ramarao who have identified the Manganese deposits in this area have done so by observing outcrops of lateritized ore with a distinct jet black colour. Using this as ground clue, few trenches used to be opened on the identified Manganeferous laterite zone in the virgin area to expose the ore body or bodies. Once the ore body is touched, one or two exploratory benches used to be developed on the ore body. Based on the quality and quantity of the ore body, the benches used to be extended both horizontally and vertically, eventually developing it into a systematic mine pit. During the course of this mining activity, other unexposed ore bodies used to be exposed and those were also exploited in the same manner. The method followed had an advantage, in that, it produced ore on regular basis and also added new resources to be exploited in future. Thus the method of exploration followed throughout the history was by way of trenching, pitting and exploratory mining which yielded about 14 million tonnes of Manganese ore from 40 individual pits during about 100 years of mining. 7

8 EXPLORATION AND RESOURCE ESTIMATION AS PER UNFC Because of the unpredictable nature of Manganese ore bodies, no exploratory drilling was carried out in the past, though some drilling was done by Geological Survey of India without any fruitful results. From , systematic grid pattern drilling was carried out to assess the resources. Taking into consideration the geology and the ore behavior, 50m grid based core drilling covering the entire lease area was carried out. In total, about 50000m of drilling is carried out in about 800 holes. The average depth covered is 60m from exposed surface. This drilling is carried out to achieve the following objectives: To know the depth continuity of exposed ore bodies in the working pits. To intersect hidden ore bodies inside the pits. To explore virgin plateau area for new ore bodies. To estimate reserves and resources using data obtained by drilling. 8

9 Reserves and Resources of Mn ore: Manganese ore reserves and Resources as on are as under: ML-2678 UNFC Code Quantity (million tons) Grade (Mn %) A. Total Mineral Reserve Proved Mineral Reserve Probable mineral Reserve B. Total Remaining resources 0.99 Feasibility mineral Resource Total Reserves + Resources ML 2679 UNFC Code Quantity (million tons) Grade (Mn %) A. Total Mineral Reserve Proved Mineral Reserve Probable mineral Reserve B. Total Remaining resources 0.10 Feasibility mineral Resource Total Reserves + Resources

10 Open cast Mining method is followed. METHOD OF MINING AND PRODUCTION: Deep hole drilling & blasting is done in waste rock and jack hammer drilling & blasting is done in ore body. Waste material & Mineral rejects (10 to 24%Mn) are dumped/stacked separately in designated places and ore is segregated manually at sorting yard. Working mine pits are in various shapes and sizes with depths ranging from 20 m to 150m. There are 40 number of pits in the lease area, which are formed over the years, but today only fourteen major pits are being worked. The blasted material from the face is transported to sorting yard where the hand sorting is carried out to segregate different grade ores. The grades of these stacks range from 24 to 44 % Mn. with two percentage units of Mn grade range. The quality of Mn ore is depleting as compared to earlier operations which is depicted below. Year PRODUCTION (t) Mn% Total Avg.M > <28 n%

11 MANGANESE ORE BENEFICIATION : The mineral assemblage of Manganese ore consists of 50 to 55 % total metal content made up of Manganese and Iron. The rest of the ore material contains Silica, Allumina, base metal oxides and other minor constituents. The Iron and Manganese are in chemical bonding, posing a challenge for beneficiation. The following is the chemical analysis of a typical Manganese ore sample(values are in weight %). Mn Fe SiO2 Al2O3 P S MgO TiO2 Na2O K2O L.O.I To improve Mn grades, screening is carried out to separate different sized Lumpy ores and fines. During this process, the screened concentrates of mm size show 1 to 2 % units improvement in Mn grades. Apart from simple screening, a combined process of crushing, wet scrubbing, screening and wet jigging is being carried out on a pilot plant scale which improves the grade by 5-6 % units in concentrate and the recovery(quantity-wise) will be about 32%. 11

12 FLOW CHART OF CRUSHING, SCRUBBING AND JIGGING (WET PROCESS) Jaw Crusher mm + 40 mm ROM of Specified Grade Screen Concentrate (40 mm) Middling Jig - 40 mm Tails Drum Scrubber Hutch Wet Screen mm mm - 5 mm mm -5 mm stock 12

13 RESULTS OF WET PROCESS OF MANGANESE ORE BENEFICIATION Feed/product detail Qty, Wt% Mn% Fe% Received from Mines Feed to crushing, scrubbing and screening Crushing, scrubbing and screeningproducts mm mm mm mm mm (100 #) mm (-100#+325#) mm (-325#) not retrievable Total Jigging Feed (5-40 mm sizes from the above process) Jigging products Concentrate mm Middling mm Tailing mm Hutch not retrievable -1 mm Total

14 Experiment of pneumatic jigging used for upgradation of -10mm size material was carried out for the sizes 1-3mm, 3-6mm and 6-10mm (laboratory/pilot scale) showed improvement in Mn grades up to 3-4% units. 14

15 RESULTS OF PNEUMATIC JIGGING Size Wt% Mn% Fe% Feed mm Concentrate Middling/Tailing Size Wt% Mn% Fe% Feed mm Concentrate Middling/Tailing Size Wt% Mn% Fe% Feed mm Concentrate Middling/Tailing

16 The experiment of reduction roasting was carried out for -10mm size Mn ore, using 1-3mm, 1-6mm, 6-10mm and 1-10mm was carried out on a laboratory scale which showed encouraging results. RESULTS OF REDUCTION ROASTING EXPERIMENT FOR MANGANESE ORE Size 1-3 MM 1-6MM 6-10MM 1-10MM Feed Mn ore 100% 100% 100% 100% Feed Sample Mn:Fe 33.93: : : :22.08 Products MAG N-MAG MAG N-MAG MAG N-MAG MAG N-MAG Percentage Mn% Fe%

17 MARKET SCENERIO Prior to stoppage of Mines in the year 2011, nearly 50% of Mn ore used to be exported and remaining 50% used to be sold domestically. After the reopening of mines in 2013, the ore produced is sold domestically through e- auction and partially used for captive consumption. SMIORE Mn ore is being sold throughout India starting from Kerala to Meghalaya. The major buyers are in Andhra Pradesh, Chattisgarh, Tamil Nadu, Goa, Karnataka, West Bengal. In general, Lumpy Ore with +26% Mn has demand in the market & is being sold regularly. Though the ore having less than 26% Mn has no market demand, last year Mn Ore fines of 20% grade have been sold in a small quantity. CONCLUSIONS AND RECOMMENDATIONS The present threshold value for Manganese ore has to be continued as 10%Mn. 17

18 THANK YOU 18