Exploration Targets for the South Braemar Project, South Australia

Transcription

1 Exploration Targets for the South Braemar Project, South Australia 25 th November 2013 H&S Consultants ( H&SC ) was requested by Carpentaria Exploration Limited ( CAP ) to complete an assessment of the Exploration Targets for its South Braemar Iron project in South Australia. The project is located 250km north north east of Adelaide and 170km east of Port Pirie. The project lies within two contiguous Exploration Licences (EL) granted to CAP and Maosen Australia Pty Limited. EL 4395 South Dam is 100% owned by CAP while EL 3998, now EL 5181, is under a joint venture agreement with Maosen (Braemar JV). CAP manages exploration for the project. The aim of the assessment is to evaluate the project area for magnetite Exploration Targets in the Braemar Iron Fm. H&SC has completed similar tasks for CAP s Hawsons Project in NSW and for Minotaur s Mutooroo Project in SA. The Braemar basin is believed to occur over an area of 7,000 to 8,000km 2. Mineralisation consists of stratabound, disseminated fine grained magnetite in siltstones and diamictites of the Neoproterozoic-aged Adelaide Fold Belt that locally have been complexly folded, including isoclinal folding, with offset faulting. Metamorphic grade is lower greenschist with the host units relatively soft unlike typical Banded Iron Formation (BIF). The Braemar Ironstone Formation is the host stratigraphic unit and comprises a series of narrow, strike extensive magnetite-bearing sediments with variable dips. Large areas of the prospective stratigraphy are concealed by transported ferricrete and other younger cover. The base of oxidation due to weathering over the prospective unit is estimated to average between 60 and 80m in depth. The airborne magnetic data clearly indicates the magnetite sediments as a folded, narrow, high amplitude magnetic response. Exploration work completed by CAP in 2012 includes modelling of airborne and ground magnetic data, and limited RC drilling, 3 holes for 500m. The drilling has tested two different sections of a single magnetic anomaly within the sedimentary sequence and has identified a m thick (true thickness), magnetite-bearing package of siltstone and diamictite. The drilling results were announced to the ASX on the 29th January Initial sampling of the RC drilling consisted of 500 1m samples subsequently reduced to 87 composite samples, mostly 6m in length, using the spear sampling method. All 1m samples were subject to magnetic susceptibility and hand held XRF measurements, whilst the composites were subject to multielement analysis by ICP. A subsequent suite of 59 samples (75 samples including QAQC samples) were tested for magnetite using the Davis Tube Recovery ( DTR ) method. Analysis of the magnetic fraction for each of the 59 DTR composite samples yielded variable iron grades for the concentrate of between 56-68% Fe with between 6-10% SiO 2, Al 2 O 3, to 0.039% P, to 0.017% S and to LOI. 5 samples had insufficient material for concentrate analysis. Multielement analyses of the drilled material indicated some localised variation in sediment composition for the magnetite bearing sediments. Petrographic analysis using transmitted and reflected light microscopy concluded that the samples had considerable affinity with other iron mineralisation within the Braemar basin and are considered of the same type.

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3 Appendix 1 Figure 1 shows the extent of the Braemar sedimentary basin and the location of CAP s South Braemar Project. Figure 1 CAP s South Braemar Iron Project Location Map Table 1 shows the current resource estimates for magnetite deposits in the Braemar basin. Table 1 Iron/Magnetite Resource Estimates for the Braemar Basin Company Deposit Licence Status Havilah Grants 3895 Inferred Resource of 24% Fe applying an 18% Fe cut off grade. (No DTR results available) Havilah Maldorky Indicated Resource 30% Fe with pit design (no DTR 3895 results available) Minotaur Muster Dam 3745 Inferred 1.5Bt at 15.2% DTR; 69-70% in Fe concentrate Carpentaria Hawsons 6979/7841 Inferred 1.4Bt at 15.5% DTR; 69-70% Fe in concentrate Royal Razorback 4267 Indicated & Inferred Resources of 21% Fe (no DTR Ridge results available) Royal Ironback Hill 3927 Inferred Resources of 21% Fe (no DTR results available) Figure 2 shows the regional scale airborne magnetic data for the area under consideration, indicating the high amplitude magnetic responses associated with the Braemar Iron Formation. The 3

4 nearest known resource is Ironback Hill located 10km to the north of the northern boundary of EL 5181 with a published Inferred Resource estimate of 21% Fe (no DTR grades available). The anomaly within CAP s South Braemar Project has been split into 4 sub-sections with the South Dam section in EL 4395 separated from the others on EL 5181 i.e. Braemar JV West (W), Central (C) and East (E); see Figure 2 below. Figure 2 Regional Airborne Magnetic Image of CAP s South Braemar Iron Project Ironback Hill Deposit W C E 4

5 MAGNETIC MODELLING Forward 2.5D magnetic modelling of high resolution, 100m line spaced, 30m nominal sensor clearance, aeromagnetic data over South Dam sub-section has indicated an 80 o W dip (consistent with field measurements) to the host siltstone unit (Figure 3). This dip is interpreted to be similar going northwards along strike into EL 5181 (Braemar W) towards the fold hinge (see Figure 2). Figure 3 Magnetic Modelling of the South Dam Aeromagnetic response Flight lines and first vertical derivative image of high resolution aeromagnetic survey, South Dam (black is flight line L10870) L D Magnetic Model of Aeromagnetic 1 st VD Profile ( mN) 5

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7 Figure 4 Braemar JV (EL5181) W, C & E Target Areas W C E Interpreted Fault 7

8 Figure 5 shows a north-south cross section through CAP s 3D magnetic inversion model for the fold nose area in the Braemar C area, identified by CAP as Area B. The model is rather inconclusive as to the geometry of the magnetic source. Figure 5 Braemar C 3D Magnetic Model Cross Section (Area B) 8

9 Ground magnetic data acquired over the Braemar E anomaly, identified by CAP as Area D, (Figure 6) indicates potential for greater structural complexity. A cursory interpretation completed by H&SC, shows faults controlling the distribution of the magnetite siltstone, including a possible NE striking offset fault and a N-S truncating fault. The interpreted structural complexity may serve to indicate that the optimal drillhole spacing for resource definition might be considerably shorter than used elsewhere in the Braemar basin. Figure 6 Braemar E RTP Ground Magnetic Image & Interpretation Map (Area D) Interpreted Fault Figure 7 shows the magnetic model for line L N (refer Figure 6) of the ground magnetic data with the CAP RC drilling as black traces and magnetic susceptibility amplitudes plotted along the drill trace. The model indicates a thick sequence of steep east dipping magnetic units with the top of the unit/base of oxidation estimated from the model to be between 40 to 90 m below surface and 40 m deeper than subsequent drilling indications. CAP has identified a remanent magnetic field component of unknown direction and amplitude at Braemar and the model in Figure 7 assumes no remanent magnetic component in the model calculation. Subsequently dip directions and other parameters like depth estimation cannot be accurately resolved in this model. Two additional magnetic features of lower amplitude, to the east of the main anomaly, remain unexplained and are not considered in the current Exploration Target size estimations. This is due to the lower magnetic intensity associated with their TMI responses. Appendix 2 contains a representation of the 3D model for Area D which accounts for the remanent magnetic component discussed above. 9

10 Figure 7 Braemar E 2.5D Ground Magnetic Model Line N Figure 8 shows the magnetic model of the ground magnetic data collected 400 m north of line L N and also indicates a thick sequence of magnetic units dipping moderately to steeply eastwards with the top of the unit/base of oxidation about 60m below surface (consistent with the model to the south). There is also indication of a reduction in the intensity of magnetite within the target unit on this section (cf model susceptibilities and TMI amplitudes L N). The model in Figure 8 also assumes no remanent component to the magnetic field in the calculations Figure 8 Braemar E 2.5D Ground Magnetic Model Line N 10

11 DRILLING RESULTS Drilling on the Braemar JV consisted of three RC holes for a total of 500m using a Schram drill rig. Bulk samples were captured via a rig-mounted cyclone in large plastic bags on 1 m intervals. A smaller reference sample for each 1 m was split from the cyclone and stored in a calico bag. The bulk sample was subject to a magnetic susceptibility measurement using a magrock digital magnetic susceptibility meter. A single 30 second XRF determination was also taken for each bulk sample using an Olympus Delta hand held XRF analyser. Sub-sampling of the RC material consisted of mostly 6 m composites using a 50 mm diameter spear sampler. Geological/magnetic susceptibility control was locally used to determine the composite interval. Sample weights varied between 3 and 5 kg. A QAQC sampling programme consisted of 1 in 20 composite duplicates for a total of 10 samples, insertion of a magnetite standard (1 per batch for a total of 3) and 6 blank gravels. Appendix 3 has more details of the QAQC results. 106 samples as composites, including QAQC samples, were sent to ALS for multi-element analysis (33 elements - ME-ICP61), 4 acid digest with ICP-OES finish. Gold analysis was by Au-AA23, 30g fire assay with AA finish. 75 samples, including QAQC samples, were sent for DTR analysis with a standard 38um grind (ME-XRF21c & ME-XRF21h), using wet magnetic separation Geological logging consisted of hardcopy recording of lithology, mineralisation and alteration from chip trays for individual 1m samples. Data was entered into an Excel spreadsheet. The drilling provided confirmation of magnetite as the source of the magnetism along with information on depth of cover, likely minimum thickness of the magnetite-bearing units and host lithotypes. Magnetite-bearing siltstones and diamictites typical of the Braemar Iron Formation were recorded. Drilling typically intersected 3-4 m of transported cover followed by m of oxidised residual clays and then oxidised siltstone for m. A reasonable correlation between magnetic susceptibility and handheld XRF measured iron grade is evident. Figure 9 shows the correlation of downhole handheld magnetic susceptibility measurements with handheld XRF iron values from two holes drilled at the Braemar E area. High XRF iron values at the top of the holes (left hand side of the figure) indicate oxidised magnetic siltstone rather than any barren/low grade hanging wall sequence. 11

12 Figure 9 Braemar E Correlation of Handheld XRF Fe readings & Mag Sus in Drillholes (red trace = magnetic susceptibility SI; black trace = XRF iron value %) Figure 10 shows the reasonably good correlation between the DTR grade and handheld magnetic susceptibility values with the latter composited to the same intervals as the DTR data. The relationship is not linear but the correlation coefficient is sufficiently high enough to allow for handheld magnetic susceptibility determination to be used as a strong indicator of potentially economic magnetite mineralisation. The correlation is not sufficiently strong enough for handheld magnetic susceptibility to act as a proxy for estimation of recovered magnetic fraction grades for resource modelling except for peripheral samples or low grade DTR samples within the mineralisation that do not have concentrate assays. Figure 10 Braemar E Correlation of Composites for DTR Grades & Mag Sus in Drillholes 12

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14 Braemar E Drilling Discussion Drillholes RC12BM001 & 002 (EL 5181) tested the high magnetic amplitude anomaly in the east of the Braemar JV area referred to by CAP as Area D. A mixed sequence of siltstones and diamictites was encountered typical of the Braemar Iron Formation. An interpreted cross section of the drillholes is included as Figure 11. Both holes stopped in magnetite mineralisation and did not necessarily pass into the footwall of the deposit. Figure 11 Braemar E Drillhole Section Line 21100N Magnetic correlation of individual units between the two holes is difficult but CAP has made an attempt relying on both handheld XRF iron grade and magnetic susceptibility (Figure 12) concluding the beds are vertically dipping. 14

15 Figure 12 Braemar E Area D Drillhole Section Line 21100N Correlation of Lithologies If the beds are dipping vertically then there is very little overlap between holes and thus stratigraphic correlation is very difficult. However logging has identified a 9 m downhole thickness sandstone in Hole 002 with low DTR and mag sus. Towards the base of Hole 001 there is a fine grained sandstone diamictite (the dia5 logging code) of a similar downhole thickness with a similar drop in magnetic susceptibility to the sandstone in Hole 002. If the two are the same unit then the implication is a 45 o dip to the east for the magnetite units. A further complication is that a second diamictite dia5 zone has been identified in Hole 001 which has similar properties to the unit in Hole 002. If they are the same unit then the implication is that the beds dip 30 o to the west. The width of the unit in Figures 11 and 12 varies between 100 and 200m, although H&SC would suggest that in Figure 12 the high iron assay values in the oxide zone of drillhole RC12BRP002 would suggest that the eastern boundary of the interpreted magnetic siltstone could be extended eastwards another 50 m making it 150 m thick. The flatter dipping interpretations would imply something between 100 and 150m true thickness. Alternative interpretations to the steep east - vertical dip can exist, for example the 45 o dip to east mentioned above or a flattish (30 o ) dip perhaps to the west. Regardless, it still leaves the mineralisation units having a true width in the order of 100 to 150m. 15

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18 Appendix 2-3D mag model Braemar E (Area D) 18

19 Appendix 3 - QAQC Results Magnetic Sus meter vs CSIRO Standard. Magnetic Susceptibility (SI) CSIRO Std Magrock 0.08 SI SI SI

20 Duplicates for Head & Con Grade XRF Assays 20

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