ESTABLISHES SOLID GROWTH FOUNDATION IN WORLD-CLASS SOUTHERN CROSS DOMAIN
- Total Maiden JORC 2012 Inferred Mineral Resource Estimate for the Mt Dimer Gold and Silver Project includes 722kt @ 10 g/t Au for 48,545 ounces of gold and 3.84 g/t Ag for 89,011 ounces of Silver
- Resource includes the low-grade near surface laterite component, as well as the vein hosted Resource
- Resource split into above and below 380mRL (surface approx. 500mRL) using two different cut offs to take into account higher potential mining costs (Figure 7)
- Resource remains open to the south and down dip, with strong potential to extend the mineralisation along strike to the south
- Maiden Resource solidifies TSC’s position in the highly prospective Southern Cross Goldfields District in WA and provides strong base for future growth
- TSC remains confident additional mineralisation may be defined outside of drilling completed to date either on the mining lease or the exploration license to the west
- Planning for follow up work programs is underway on the exploration license which equals approximately 87% of the overall land package at Mt Dimer
Twenty Seven Co. Limited (ASX: TSC) (“TSC” or “the Company”) is pleased to report a maiden JORC 2012 Inferred Mineral Resource Estimate at its 100% owned Mt Dimer Gold Project, located in the world‐class Marda-Diemals Greenstone Belt WA (refer Figure 1).
The Total Maiden JORC 2012 Inferred Mineral Resource Estimate for the Mt Dimer Gold and Silver Project includes 722kt @ 2.10 g/t Au for 48,545 ounces of gold and 3.84 g/t Ag for 89,011 ounces of Silver.
The Mt Dimer Gold Resource is the maiden JORC classified mineral resource to be reported at the Mt Dimer Gold Project, and highlights the potential for further gold and silver resources to be identified along the mineralised corridor within Mt Dimer and the surrounding tenements. The Inferred Mineral Resource is summarised in Table 1 below.
Further, recent soil geochemical sampling undertaken (see ASX release dated 13 May 2021) over the exploration licenses to the west of the Mt Dimer Ming Lease (“MDML”) shows the potential for further mineralisation to be defined within the greater project area.
Table 1:Inferred Resource Classification using a 0.5g/t and 1g/t Au cut-off grades
As displayed in the above table, most of the Mineral Resource is contained within the vein system and not the laterite portion.
A cut off 1.0g/t Au has been applied to the Resource below the 380mRL. In doing this, the author recognises that mining costs increase with depth and as such the cut-off grade has been increased, which takes in to account the Reasonable Prospects of Eventual Economic Evaluation (“RPEEE”) criteria under the JORC code, see Figure 7.
Figure 1: Mt Dimer Gold Project Location Plan
- The current in‐situ, drill defined Mineral Resource has been reported a cut‐off of 0.5g/t and 1.0g/t Au.
- The mineralised zones that form the basis of the Inferred Resource show good lateral continuity and are based on data from 2 x diamond drill holes (308m) and 90 x reverse circulation drill holes (10,787m). The total meterage includes holes that have been drilled historically as well as holes that were drilled by Cadre Resources in 2017 and TSC in 2021.
- The mineralisation at Mt Dimer has been interpreted as a series of 7 x discrete mineralised domains with 5 x striking 150 degrees and dipping approximately 75-80 degrees west, a sixth domain also strikes at 150 degrees but has a shallower dip of 47 degrees west, and the final domain encompasses near surface laterite mineralisation, which is sub-horizontal and generally follows the strike of the underlying vein related mineralisation (see figure 2 for the 7 x domain locations).
- The total mineralisation has been delineated over a strike length of approximately 740m with a down dip extent of approximately 190m and an average thickness of anywhere from 1m up to 30m.
- No high-grade mineralising plunge was identified within the Mt Dimer Gold-Silver deposit
- The Mineral Resource has been defined on the following search ellipse parameters:
Table 2: Search ellipse parameters
- Block model was rotated using the WF1-5 search parameters
- Block sizes were 2m E x 10m N and 1m RL
- Gold grades were top cut to 21 ppm and the silver grades were top cut to 35 ppm
- Any grades within the 1 meter composite file that were less than the detection limit were assigned as half the detection limit
- Any intervals that were not assayed but were within a mineralised wireframe were assigned half the detection limit of the corresponding element
- Discretisation was 1E x 4N x 2RL
- Two search passes were undertaken and includes using a maximum of 20 x informing points and a minimum of 3 for both passes
- A lower cut-off grade for the laterite and resource above the 380mRL was set at 0.5g/t Au giving consideration to the spatial distribution of various grade rages and potential future economic parameters.
- A lower cut-off of 1g/t Au for the resource below the 380mRL level was used to take into account the increased mining costs at deeper levels.
- Most of the Resource at Mt Dimer has been classified as Inferred due to the reliance on predominantly historical drilling and inability to fully validate all of the associated data.
Overview Notes on the Inferred Mineral Resource
- Discrepancy in summation may occur due to rounding.
- Ordinary Kriging has been utilised as the interpolation method for the mineralised domains.
- Modelling and estimations were undertaken using Micromine
- Refer to the JORC 2012 Table attached to this announcement and the Summary of Mineral Resource Estimate process for further details.
Figure 2: Mt Dimer Wireframes coloured by code – Looking North East
Figure 3: Mt Dimer Wireframes coloured by code with the open pit shell – Looking North East
Figure 4: Block model coloured by Au_ppm grade – Looking North East
Figure 5: Mt Dimer oblique BM coloured by Au_ppm – Looking North East
Figure 6: Mt Dimer cross Section with the block model coloured by Au_ppm
Figure 7: Block coloured by grade. The blue line represents the 380mRL line whereby the Resource has been split to take in to account higher mining costs at depth
Summary of Mt Dimer Mineral Resource Estimate
Geology, Geological Interpretation and Mineralisation
The Mt Dimer Gold Project is hosted within quartz veins which are themselves hosted within a sheared ultramafic which is heavily talc ± Chlorite ± actinolite altered and which is all contained within the Marda Greenstone Belt.
Gold mineralisation is interpreted as steep westerly‐dipping quartz veins which to date has been delineated over a strike length of approximately 740m, a down dip extent of approximately 190m and an average thickness of between 5 to 30m.
Gold (Au) mineralisation is also associated with elevated Silver (Ag), Lead (Pb), Arsenic (As), Sulphide (S) and Zinc (Zn). Only the Gold and Silver has been interpolated within the resource.
Drill Hole Database
The drillhole database created for the Mt Dimer region contains data for 656 individual drillholes. A Subset has been applied to the database for the estimation of Mt Dimer, whereby only drill holes with data that can be verified against historical records have been used. The most recent drill holes by a previous explorer in 2017 and the 2021 reverse circulation holes drilled by TSC have also been used in the interpolation of the Resource.
In total, 2 x diamond drill holes for 308m, and 90 x reverse circulation drill holes for 10,787m have been used in the Resource Estimation. The total meterage includes holes that have been drilled historically as well as holes that were drilled by a recent previous explorer in 2017 and TSC in 2021.
Drillhole sections have been predominately drilled on an azimuth of ~062 degrees, with a general dip of ‐60 degrees, with 2 x holes being drilled in the opposite direction but still at -60 degrees.
Sampling for the 2021 drilling was predominantly taken on 1m intervals using a cone splitter and assayed for a full 33 multi-element suite plus Au within the mineralised zone and 4m composites when outside the mineralised zone which was only assayed for Au. All samples were weighed when they were received at the lab. If any 4m composites came back with >0.5ppm Au then the secondary corresponding samples were picked-up and sent to the lab for Au+48 elements, (see JORC table 1 for full explanation on sampling).
The 2017 drilling was selectively assayed in zones of interest and only for Au. The method of sampling is unknown.
The historical drilling was routinely assayed on either 1m intervals in areas of interest and 4m or 5m in the rest of the hole. The samples were sampled via Riffle Split.
Sampling and logging during 2021 was supervised by a qualified geologist who was competent in the style of mineralisation, it is unknown what level of supervision was used for the logging of the historical holes.
The 2021 samples have been analysed via a 50g fire assay with AAS finish and a 33-multi element suite using ICP-AES. The 2017 samples were assayed using 50g fire assay with AAS finish. The historical holes were assayed using the lab technique Au (313) (30g fire assay with AAS finish) and 4 other elements Ag, Cu, Pb and Zn, using an unknown assay technique.
(a) Geological Modelling
Twenty Seven Co has undertaken a Mineral Resource of the Mt Dimer Deposit by importing the most recent and the historical drilling data from MS access into Micromine 3D geological software. The data was then validated for major errors such as, but not limited to; overlapping intervals, intervals beyond hole depth and erroneous survey details. Mineralisation wireframes have been generated by creating lithology and gold grade wireframes and applying a cut-off grade of 0.1 g/t Au.
Table 3: Block model dimensions
|Block Mode Dimensions|
|Parent Block size||2||10||1|
Table 4: Wireframe vs Block model volumes
|Wireframe Name||Volume in M3 of the Wireframes||Volume in m3 of the BM||Difference in M3|
The reason for the difference in the wireframes vs the block model volumes is that the vein gets thin towards the periphery of the deposit and at depth.
Laterite, completely/highly weathered, transitional and fresh oxidation surfaces have been created using weathering data contained within the drillhole lithology table.
Each of the 7 x domains (Figure 2) were independently flagged within the assay data file and each of the domains had variography undertaken separately to see if any grade continuity could be seen. It was noticed that 5 of the domains were comparable (Veins 1-5) to each other, whereas vein 6, due to its differing dip had separate variography parameters. The laterite domain utilizing the same variography as veins 1-5. The variograms parameters that were used were nugget of zero, range of 140 and partial sill of 24.7.
Determining the optimal block size is the first step in the Kriging process. A block sizes of 2m E x 10m N x 1m RL was used.
Various search ellipse distances have been tested for each of the 7 x domains at the various proportions in order to determine the optimal search. A search ellipse of each of the domains is as follows:
|Search distance (m)||Search ellipse|
|WF Name||Along Strike||Down dip||Down hole||Strike||Dip||Plunge|
Figure 8: Search ellipse parameters
The final block model included discretisation parameters of 1E x 4N x 2RL.
(d) Block Model Construction
A block model has been created encompassing the Mt Dimer mineralisation. The block model has been constructed using a parent block size of 2m E by 10m N by 1m RL with sub‐blocking down to 2m E by 5m N by 0.5m RL for effective boundary definition. All sub‐cells have been estimated at the scale of the parent block and therefore have the same estimated grade.
Ordinary Kriging has been utilised as the interpolation method for the mineralised domains. The interpolations have been undertaken using hard boundaries.
Mining by Taipan Resources was undertaken at the Mt Dimer Deposit in the mid 1990s. Blocks that are contained within the open pit, and hence have already been mined were flagged within the block model and interpolated along with the rest of the block model.
On completion of the model the “mined” blocks were flagged within the block model and then reported out.
Visual comparison of composite sample grade and block grade has been conducted in cross section and in plan. Results show the majority of domains display a good comparison between the input composites and corresponding block grades.
No density data was supplied within the drill hole database, although the density applied to the Resource estimate is within an acceptable range, 2.1cm3 for Laterite, 2.0 cm3 for Oxide material, 2.5 cm3 for Transitional material and 2.7 cm3 for Fresh material, is it strongly recommended that any future drilling or site visit undertake density measurements to better define the true density nature of the Mt Dimer deposit.
(e) Resource Classification
Classification of the Inferred Mineral Resource Estimate at Mt Dimer has been completed in accordance with the Australasian Code for Reporting of Mineral Resources and Ore Reserves (the JORC Code), as prepared by the Joint Ore Reserve Committee of the AusIMM, and AIG.
All classifications and terminologies have been adhered to. All directions and recommendations have been followed, in keeping with the spirit of the code. The categories of Mineral Resource as outlined by the code are as follows:
- Measured ‐ tonnage, densities, shape, physical characteristics, grade and mineral content can be estimated with a high level of
- Indicated ‐ tonnage, densities, shape, physical characteristics, grade and mineral content can be estimated with a reasonable level of
- Inferred ‐ tonnage, grade, and mineral content can be estimated with a reduced level of
- Exploration Target – an Exploration Target is a statement or estimate of the exploration potential of a mineral deposit in a defined geological setting where the statement or estimate, quoted as a range of tonnes and a tonnage of grade (or quality), relates to mineralisation for which there has been insufficient exploration to estimate a Mineral Resource.
The Resource Classification of Inferred has been applied to the Mineral Resource Estimate based primarily on the number of informing points for each block however the drilling data spacing, grade and geological continuity, data integrity, and lack of reliable density date has also been taken into account. Only the Inferred Resource has been reported here.
The method to generate the classification within the block model is as follows:
- Pass priorities – ‘first pass’ is prioritised over ‘Second pass’.
- Class 1 – a block with a minimum of 10 informing sample points in the first pass estimation.
- Class 2 – a block with less than 10 informing sample points in the first pass estimation and a minimum of 10 informing sample points in the second pass estimation.
- Class 3 – a block with less than 10 informing sample points in the first pass estimation and less than 10 informing sample points in the second pass estimation.
A class is assigned independently for Au and for Ag due to the fact that a proportion of drilling has Au but not Ag assay data. In some instances, a block will have a classification of 3 but will not have grade this effectively represents any block that had no informing sample points in the second pass estimation.
Figure 9: Classification of each block