Proposed Limpopo West Mine Concept Study ... - SRK Consulting

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SRK Consulting: 447493: Limpopo West Geochem Page 35Table 5-5: Summary of Findings – Acid Rock Drainage Assessment by IGSAreasNorthWesternSouthEasternNorthernAreaGeologyFull succession of geology and coalFull succession of geology and coalWeathered Area down to Middle EccaWeathered Area down to Middle EccaARDpotentialPAFNAFPAFNAFPAFPAFNAFBelow Coal Zone 2 PAF SandstoneGrootegeluk Discard from Grootegeluk Plant PAF DiscardPotential ProblematicLayers/MaterialAlternating layers of Mudstoneand Shale interbedded with coalAlternating layers of Mudstoneand Shale interbedded with coalAdditional Sampling to identifyspecific layerAdditional Sampling to identifyspecific layerGenerally this study concluded that the samples from the full succession of geology (NW and SEareas) and coal indicated acid and neutral generating potential, with the PAF material limited to adepth of between 50 m and 80 m. This depth corresponds to the pyrite bearing lithologies. Thesamples collected from the weathered areas (SE and N) are both PAF and NAF. Additional samplingis required to confirm specific PAF lithologies. The sandstone collected coal zone 2 and the discardsamples have both been classified as PAF.5.4.2 Sasol Mafutha (SRK, 2011)As part of the Environmental Impact Assessment (EIA) undertaken by SRK, an assessment wascarried out to determine the geochemical characteristics of geological materials that will be exposed,disturbed and/or deposited by mining operations at Sasol Mafutha.During this assessment, a total of 15 composites were analysed. These samples were collected fromboreholes spread across the Northern (Ringbult) and Southern (Grootwater and Groenfontein) areasof the overall lease area, and included coal exposed in the pit walls of the Bulk Sample pit in thecentral area. The samples were composited as shown in Table 5-6.Table 5-6: Summary of Mafutha geochemical samplesSample ID Sasol Lithocodes DescriptionSRK-01 CON ConglomerateSRK-02MST-SID- CSHSiderite, 10% bright coal, coal shale, mudstone,40% bright coal, Mudstone, Bright StrippedBanded coal, mudstoneSRK-03 PIR-CSH Pyrite & Coal shaleSRK-04 SST SandstoneSRK-05 SAN SandSRK-06 MST-C Mudstone & CoalSRK-07 CSH Coal ShaleSRK-08 MST MudstoneSRK-09 SST SandstoneSRK-10 MST-C-CS Mudstone, Coal, Coal ShaleSRK-11 MST-C Mudstone & CoalSRK-12 SID-C-MST Siderite, Coal and MudstoneSRK13 MST MudstoneSRK-14 C CoalSRK-15 C (Pit Wall) Coal seamGOGP/LAKJ Report_April2013_19April2013 (1)_Final_Ludi_22052013 April 2013
SRK Consulting: 447493: Limpopo West Geochem Page 36Laboratory analysis undertaken on the core samples included the following:Elemental Composition by total digestion (Aqua Regia);Distilled Water Extract analysed for pH, EC, cations, anions and metals and metalloids by ICP;Acid Base Accounting (ABA) with sulfur speciation;Net Acid Generation;XRD for mineralogical determination;XRF for major elements; andTrace metals / metalloids by quantitative ICP scans.The water sample collected from the Bulk sample test pit located in the central are, taken torepresent shallow aquifer groundwater seepage across the pit, was analysed for the following :Physico-chemical parameters - pH, TDS;Major anions – HCO3, SO 4, Cl; F NO3; and Major cations – Ca, Mg; Na, K.The results of the study can be summarised as follows:The mineralogy results indicated that the samples are dominated by quartz, clay mineralskaolinite and smectite, mica muscovite with the ratio of the minerals being variable in thedifferent lithologies.Acid generating pyrite (FeS 2 ) was observed in the mudstone sample of the overburden and coalseam material with trace amounts detected in the sandstone sample.Acid neutralising minerals are present in all the lithologies analysed with the dominant carbonatemineral being calcite (CaCO 3 ) found in trace amounts in all samples, except sandstone in theinterburden where ankerite (Ca(Fe, Mg, Mn)(CO 3 ) 2 ) was dominant.The ABA results indicated that most of the samples contain low sulfide resulting in low AP, withthe exception of mudstone from the overburden and the coal seam samples. The NPR indicatedthat the mudstone, sandstone and coal lithologies are potentially acid generating, the rest of thelithologies are non acid generating.The NAG test is generally used to confirm ABA results. Table 5-7 presents a summary of theABA and NAG test results. NAG results indicate that the lithologies associated with coal (MST-C, SST, and C) have the potential to generate acidity.The 1:4 solid to liquid ratio distilled water leach test results indicated that the overburdenlithologies seem to mobilise higher concentrations of metals than the interburden lithologies, withaluminium and iron being the only metals that are consistently mobilised at elevatedconcentrations from most of the overburden and interburden lithologies.The Bulk Pit water quality was slightly alkaline. the quality was characterised by high alkalinity,low sulfate concentrations and low concentrations of metals indicating that the water quality ofthe pit lake has not been significantly affected by acid ARD. The ratio of the sum of calcium andmagnesium to sulfate is above 1, indicating that carbonate dissolution is controlling pH.Table 5-7: ABA and NAG test results for the Sasol Mafutha Geochemical AssessmentWaste TypeOverburdenInterburdenLithologyCONSANMST-CMSTMST-CMSTMST-SID- CSHPIR-CSHSSTCSHABAassessmentNAGassessmentCommentHi pH/ S’fide ND/ Hi NPRS’fide ND/ Lo NPRLo S’fide/ Hi NPRS’fide dominates/ Lo NPRLo S’fide but NP NDRelatively Hi S’fide / Hi NPRHi pH/ Lo Sulfide/ Hi NPRHi pH/ Lo S’fide/ Hi NPRHi pH/ S’fide ND/ Hi NPRLo pH/ S’fide present/Marginal NPRDecisionGOGP/LAKJ Report_April2013_19April2013 (1)_Final_Ludi_22052013 April 2013
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Proposed Limpopo West Mine Concept Study ... - SRK Consulting

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