Sydney, Australia--(Newsfile Corp. - July 23, 2024) - Established gold producer Austral Gold Limited's (ASX: AGD) (TSXV: AGLD) (OTCQB: AGLDF) (Austral, AGL or the Company) is pleased to announce the filing on SEDAR+ and the ASX of a Technical Report, prepared in accordance with National Instrument 43-101 and Joint Ore Reserves Committee Code (JORC 2012), on the Casposo-Manantiales Mine Complex, dated 19 July 2024 (with an effective date of 30 April 2024).
Highlights of the Technical Report were disclosed in the Company's announcement dated 17 July 2024. The Technical Report is available on the Company's website at www.australgold.com and has been filed on SEDAR+ under the Company's profile at www.sedarplus.ca and on the ASX at www.asx.com.au. The Company confirms that the material highlights of the Technical Report as disclosed in the Company's announcement dated 17 July 2024 remains unchanged.
In addition, the Company wishes to provide further information as an addendum for the purposes of ASX Listing Rule 5.8.1 (set out below) and an updated JORC Table 1 (to its 17 July 2024) which inadvertently did not include sections 1 and 2, which is attached to this release.
COMPETENT PERSON'S STATEMENT
For the purposes of Listing Rule 5.22, the Company confirms that the updated Mineral Resource estimate for the Casposo Mine was based on work reviewed or compiled by Marcos Valencia, an independent "Qualified Person" as defined by NI 43-101 and a "Competent Person" as defined in the JORC (2012) Code, either as a Member of the Australian Institute of Geoscientists, or members in good standing of Recognised Professional Organisations in Canada and the United States.
The Competent Person is a consultant of Wampeso Holdings Inc.
The Competent Person consents to the inclusion in this announcement of the matters based on his information in the form and context in which it appears.
The Competent Person has sufficient experience which is relevant to the style of mineralisation and types of deposits under consideration and to the activities undertaken to qualify as a Competent Person as defined in the JORC (2012) Code.
Further information provided for the purposes of ASX Listing Rule 5.8.1 (to be read together with the release on 17 July 2024)
Geology and Geological Interpretation
The deposits exposed in the Casposo-Manantiales Property are typical Epithermal Low Sulphidation and they are multi-stage, open space filling events resulting in mineralized veins, breccias, stockworks and or veinlets.
This deposit type is characterized by quartz veins, hydrothermal breccia, stockworks, and veinlets units that contain gold, silver, electrum, and variable silver and iron sulphides. Alteration has been identified by Terraspec spectrometry and is typical of the Low-Sulphidation model, with broad haloes of white mica and less common kaolinite alteration around the mineralized veins, see figure 8.1.1 showing haloes formed around the mineralised structures. Silicification is the most common alteration type with multiple generations of quartz and chalcedony, which are typically accompanied by adularia and calcite. Pervasive silicification in the vein envelope is flanked by sericite-Illite-kaolinite assemblages. Kaolinite Illite-montmorillonite ± smectite (intermediate argillic alteration) can form adjacent to veins; kaolinite-alunite (advanced argillic alteration) may form along the tops of mineralised zones. Propylitic alteration dominates at depth and along the deposit margins.
Four main deposits have been geologically modelled by the team of the Casposo Mine. These structures are Manantiales, Mercado, Julieta and B-Vein and subsequently geostatistic was performed to determine the metal contents.
The mineralization frame occurs along a 10 km long WNW-ESE structural corridor. All the structures are the continuity of the main and previously exploited deposits called Kamila and from south to the north are B-Vein, Mercado, Julieta and Manantiales.
Casposo Mine is a prolific district where the mineralisation is still open and further exploration works will help to advance several targets identified by the AGL Exploration team.
Stockpiles: No geological models were constructed for the heaps' Mineral Resource estimate, as they are artificial deposits.
Sampling and Sub-Sampling Techniques
Sampling of core drilling was performed under geological criteria in which geological and geotechnical logging was performed on the core. The former was carried out by geologists for lithological, structural and mineralogical information, while the latter was done by trained personnel for recovery and RQD information.
Core recoveries were consistently high, averaging over 90%. Mineralized intervals were selected for assaying for gold and silver content. In cases where the holes were aimed for a specific target, sampling is carried out only in selected intervals of geological interest (veins, veinlets or stockworks), as well as in the adjacent footwall and hanging-wall host rock.
Sub-sampling interval size varies from a minimum of 0.3 meter to a maximum of 1.0 meters.
Diamond Saw half core splitting was conducted on HQ and NQ core holes.
Digital photographs were taken of the core to keep a permanent record. Intervals that were not assayed are in storage at the mine site.
Historic drill hole collars were surveyed with industry standard equipment, total station or Differential GPS survey instruments by internal personnel or third-party contractors.
Austral Gold undertook numerous random field checks on historic collar locations. Historic collar locations were generally found to be within ±0.5m of the expected position in the chosen datum.
The database of historical data was validated and compiled by the AGL geology department and reviewed by an Argentina based Database administrator who reconciled a representative amount of available hardcopy drill logs and assay results against the digital drill hole database.
Drilling Techniques
The Mineral Resource Estimate (MRE) was based on significant historical drilling data undertaken and collected by previous owners including Battle Mountain, Newmont, Intrepid and Troy, plus drilling conducted by AGL.
Sampling was comprised of Diamond Drilling, Reverse Circulation (RC), and Surface and Underground channels, all of which were included in the MRE.
Approximately 95% of the information was obtained from DDH (Diamond Drill Hole) type drill holes, providing a solid foundation for the MRE totaling 122,290 meters (m). Total meters drilled were 125,242 m including 2,952 m of RC drilling.
All the drilling procedures adhered to the industry standards defined by the CIM (Canadian Institute of Mining, Metallurgy, and Petroleum).
Classification
In general, classification of Mineral Resources at Casposo uses criteria based on the risk associated with the distribution of the information as follows:
- Confidence in the Au and Ag estimate.
- Reasonable prospects for eventual economic extraction.
Assessment of confidence in the estimate of grades included guidelines as outlined in NI 43-101:
- Drill data quality and quantity.
- Geological interpretation and mineralised domaining.
- The spatial continuity of mineralisation.
Quantitative criteria relating to these guidelines include data density and the kriging search distances used.
More interpretative criteria include the extent of mine depletion and to a lesser extent the rock weathering condition and in situ bulk density of the mineralised and waste material.
While Austral Gold have undertaken recent industry standard quality-controlled diamond drilling, the majority of this MRE has been based on drilling data following industry standard documentation of QA/QC protocols, drilling and sampling methodologies and assay determination methods.
The overall confidence in the geological and mineralised interpretation and domaining is considered high, due in part to the existing mine openings and surface mapping undertaken by AGL employees.
The spatial continuity of mineralisation consistently demonstrated validity and geostatistical coherence across all geological and stationary domains.
The risk assessment was properly addressed using several sources of information to configure a drill grid pattern that can assure a risk level, which aligns with AGL's expectations.
- A benchmarking study was carried out to compare similar Epithermal Low Sulphidation deposits in well-known mines like El Peñon, Cerro Bayo and Amancaya in Chile, Cerro Vanguardia, some structures in Cerro Moro and Cerro Negro in Argentina, and Mercedes in Mexico. Most cases are between 20 m to 35 m arrangement and the variability of the gold and silver distributions are key to defining a minor or major drill pattern.
- Key information was the pattern that was used in the past by AGL and previous owners of the Casposo Mine. As stated by the AGL geology team, reliable reconciliations were obtained when was used a 25 m drill hole pattern to declare and define a resource as indicated.
Finally, this information, the benchmarking inputs and the expert criteria of the Qualified Person were relevant to define the same drill grid pattern 25 m x 25 m to define indicated resources for Manantiales, Julieta, Mercado and B-Vein deposits.
Formal studies of the optimal grid distance are strongly recommended to develop these new deposits in the Casposo Mine. The main goal is to determine the optimal distance between drill holes to ensure the desired level of confidence and minimize error for a year of ore production which AGL expects to be approximately 400Kton/year.
Low-Grade Stockpiles were classified as Indicated according to their origin, operational control process, mass determination and sampling.
Sample Analysis Method
All the respective drill and channel samples were analyzed at the Casposo Mine assay laboratory located at the mine site. The Casposo laboratory lab contains all the facilities for sample preparation, fire, wet and atomic absorption assays, as well as offices, washrooms, reagents and general storage.
The sample preparation and assay procedures for the historic data comprised:
- Each drill and/or channel sample was identified with a unique sample number that is tracked throughout the assaying process. The as-received samples follow the next process of preparation:
- Weighing: ranging between 0.5 and 5.0 kg.
- Primary Crushing: jaw crushed to produce a 9.5 mm product,
- Secondary Crushing: jaw crushed to achieve 90% passing 2.00 mm (10 mesh ASTM) product,
- Splitting: a 1-in rifle to approximately 0.50 kg.
- Drying: this 0.50 kg sample was dried for 2 hours at 102° C.
- Pulverizing: 100% passing 0.15 mm (100 mesh ASTM). After pulverizing each sample, the bowl, ring, and puck assembly were disassembled with the pulverized sample and placed on a rolling cloth. The pulveriser assembly was placed back in the bowl with another sample. Two assemblies were used in an alternating fashion. The pulverized sample was rolled and transferred to a numbered envelope. Silica sand was pulverized at the end of the entire sample run in order to minimize possible contamination for the next run.
- Assaying was done by fire assaying methods (30 g charge) with a gravimetric finish. Each sample was fire-assayed using a traditional lead oxide flux as well as a known addition of silver, called in inquart. The samples are placed in gas fired assay furnaces. The fusion of the flux and inquarted sample produces a molten mixture that is poured into conical molds and cooled. The lead button formed during the fusion process is separated from the cooled slag and pounded to remove any adhering slag. The lead button is then cupelled using a magnesium oxide cupel. The remaining doré bead is flattened and weighed. The weighed doré is placed in a test tube and concentrated nitric acid added. The button is then rinsed, ammonia added, and rinsed again. The button is dried and then roasted for 5 minutes. After cooling, the gold is weighed, and gold to silver ratios are checked. If the ratio is greater than 0.40 additional silver and lead is added, and the sample is re-analyzed.
- The gold and silver present in the sample are expressed according to the following formula:
- Au (g/t) = Au (mg) / sample weight (g); and
- Ag (g/t) = (Au + Ag) (mg) - Au (mg) / sample weight (g)
External Laboratory: The AGL drill core was generated, collected and the core was analyzed by the independent and certified ALEX STEWART International, Mendoza, Argentina. The sample preparation and assay procedure for the analysis comprised:
- Senior AGL field technicians frequently visited and reviewed the drilling process and transport of the core from the hole collar to the Casposo mine logging and sampling facility. All core and samples were maintained in the enclosed and locked logging facility from where batches of bagged half core samples were subsequently transported to San Juan by vehicle directly to the ALEX STEWART Laboratory in Mendoza.
- Each drill sample was identified with a unique sample number.
- Gold analysis: The samples were assayed by method Fire Assay Fusion, AAS Finish by ALEX STEWART Laboratories Mendoza, Argentina in which sample decomposition by Fire Assay Fusion in which a 30g sample is fused with a mixture of lead oxide, sodium carbonate, borax, silica and other reagents as required, and inquarted with 6 mg of gold-free silver and then cupelled to yield a precious metal bead.
- The bead is then digested in 0.5 mL dilute nitric acid in a microwave oven, 0.5 mL concentrated hydrochloric acid is then added, and the bead is further digested in the microwave at a lower power setting. The digested solution is cooled, diluted to a total volume of 4 mL with de- mineralized water, and analyzed by atomic absorption spectroscopy against matrix-matched standards (lower limit of 0.01 g/t Au and upper Limit 10 g/t Au).
- For samples > 10 g/t Au and < 1000 g/t Au the method was implemented using Fire Assay Fusion sample decomposition and gravimetric analysis whereby a prepared 30 g sample is fused with a mixture of lead oxide, sodium carbonate, borax, silica and other reagents in order to produce a lead button. The lead button containing the precious metals is cupelled to remove the lead. The remaining gold and silver bead are parted in dilute nitric acid, annealed and weighed as gold.
- Silver analysis: The sample is assayed by ALEX STEWART Laboratories Mendoza, Argentina in which sample decomposition is via HNO3-HClO4-HF-HCl digestion (ASY 4ACID) and analysis by AAS.
- The method involves the preparation of a (0.4) g sample combined with nitric, perchloric, and hydrofluoric acids, and then evaporated to dry. Hydrochloric acid is added for further digestion, and the sample is dried again. The residue is dissolved in nitric and hydrochloric acids and transferred to a volumetric flask (100 or 250) mL. The resulting solution is diluted to volume with de-mineralized water, mixed and then analyzed by atomic absorption spectrometry against matrix-matched standards (lower limit of 2 g/t Ag and upper Limit 200 g/t Ag).
- For samples between >200 g/t Ag and < 10,000 g/t Ag the method was implemented using Fire Assay Fusion sample decomposition and gravimetric analysis whereby a prepared 30g sample is fused with a mixture of lead oxide, sodium carbonate, borax, silica and other reagents in order to produce a lead button. The lead button containing the precious metals is cupelled to remove the lead. The remaining gold and silver bead are parted in dilute nitric acid, annealed and weighed as gold. Silver is then determined by the difference in weights.
Quality Assurance and Quality Control
- A proper QAQC program was implemented by AGL following the industry standards defined by the CIM.
Internal Laboratory
Several CRM were implemented like standards, blanks and duplicates.
For the drill hole data, an internal quality control program was implemented by AGL which comprised:
- Duplicate assay pulps on 5% of volume;
- Duplicate assay splits on 5% of volume; and
- Standards inserted every 20th sample.
AGL utilized two mineral standards for the drilling:
- Casposo Lab. STD BT: Au: 2.48 ± 0.1Ag: 51.9 ± 3.61
- Casposo Lab. STD AT: Au: 68.2 ± 4.15 Ag: 943 ± 20.98
For the AGL infill drilling diamond core and Channel Sampling analysis results were obtained for standards and blanks. Accuracy is monitored by certified standards which have an accepted value plus 2 standard deviations. Additionally, precision is monitored within a percentile relative variation range of 2 standard deviations.
External Laboratory
Several CRM were implemented like standards, blanks and duplicates.
For the AGL diamond drill core, quality control procedures adopted include the insertion of a range of certified geochemical standards and blanks that were inserted methodically on a one for every 20- sample basis (5%).
AGL utilized ten mineral standards for the drilling:
- Oreas 251b: Au: 0.51 ± 0.017 Ag: 0.1 ± 0.017
- Oreas 607: Au: 0.67 ± 0.024 Ag: 5.9 ± 0.189
- Oreas 601c: Au: 0.97 ± 0.048 Ag: 50.3 ± 2.31
- Oreas 624: Au: 1.16 ± 0.053 Ag: 45.3 ± 1.26
- Oreas 603c: Au: 4.96 ± 0.186 Ag: 294 ± 13
- Oreas 609c: Au: 4.97 ± 0.260 Ag: 24.6 ± 1.03
- Oreas 610: Au: 9.83 ± 0.254 Ag: 49.4 ± 1.79
- Rock Labs SP49: Au: 18.34 ± 0.34 Ag: 60.2 ± 2.5
- Rock Labs SP47: Au: 39.88 ± 0.85 Ag: 122.3 ± 5.7
- Rock Labs OxQ75: Au: 50.3 ± 1.100 Ag: 153.9 ± 7.3
For the AGL diamond drill core, RC drilling and Channel Sampling analysis were conducted for the results for the standards and blanks. Accuracy is monitored by certified standards which have an accepted value plus 2 standard deviations and additionally precision is monitored in a percentile relative variation range within 2 standard deviations.
Estimation methodology
Stationary domains were estimated for Au and Ag were made using ordinary kriging (OK) via a three- dimensional (3D) estimation methodology. The 3D method utilises regularized composites to create an additive variable.
Drilling Database
Drill hole data was provided in MS Excel format and represents a compilation of all drilling conducted by the AGL geology team. This data was imported and reviewed in a 3D Vulcan drill hole database. The main files containing the imported fields and their descriptions are found in Table 14.1.
The grid datum used for collar and survey files is Gauss Kruger, Datum Campo Inchauspe 1969 Zone 2.
The assay table contained single fields for Au and Ag. No validation or check re-assay data were available in the data supplied. However, in the central data base managed by the AGL corporate data base administrator, the information is accessible.
An additional MS Excel table was provided by Austral Gold that contains the interpreted intercepts defining the stationary domains. Given the nature of these type of deposits, they primarily consist of veins.
These interpretations can provide a basis for the interpreted domains that were used as a guide to validate the model in 3D.
The database structure is a typical relational database to compile the information of the collar like coordinates and some descriptors of the project and type of drilling, the drill hole topography, the assay table record the information related to the grades and geological units and the lito table record geological information. Table 14.1 describes the tables and fields in the database. The holeid field serves as the key field to relate the tables.
Table 14.1: Database structure for all project.
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The QP has only undertaken basic data validation.
Geological Modelling, Stationary Domains and Composites
Weathering Surfaces: No oxidation/weathering surfaces have been provided for the MRE.
Geological Interpretation
The mineralised domains evaluated for the MRE were interpreted by the AGL geology team using a model in Leapfrog and a set of cross vertical sections. They were used to guide the 3D modelling for veins, breccias, stockwork or veinlets mineralization domains developed in Vulcan software.
For Manantiales deposit, a 3D model was developed using 3 main geological features that are mineralized Veins or hydrothermal Breccias, for both hangingwall and footwall a body of tectonic breccia was modelled and, in some cases, can bearing low grade mineralization. Also, a final envelope that include veinlets or waste rock was modelled to constrain the internal domains of mineralization.
For the remaining ore bodies, a single domain was modelled, consisting of veins or hydrothermal breccias which contain the gold and silver mineralization. This domain was defined as the main domain and an external envelope identified as a veinlet envelope was defined to constrain the main ore body.
Table 14.2: Domain codes.
| Geological Domain | Code |
| Vein and Hydrothermal Breccia | MQV |
| Hangingwall and Footwall Tectonic Breccia | BX* |
| Veinlet developed on the wall rock | VLT |
* only developed in Manantiales Deposit
Once the modelling was finished, all the drill holes considered in the estimation were flagged in a field called flag and ug into the Assay table to mark every single sample with the corresponding stationary domain (see Table 14.2). This method is developed to use the real length of the samples when the process of compositing is developed.
When the regularized composites are built, they are broken down using the physical limits of every stationary domain defined in the flag field. The regularized length choose is 0.5 m due to the high variability of the grades in the width direction and also the selected block size was0.5 m*0.5 m*0.5 m, for the main stationary domains.
When the composites are created, a regular length is selected which is related to the block size, and start in the first geological limit. Once the routine is completed, the first composite to the length is defined, and the routine will create the following until the end of the geological limit in every geological unit. It is important to note that when the routine is building the last composite, each stationary domain can create the last using a length minor or equal to the regular length defined. No compensation in length is defined in this routine. Figure 14.1 illustrates the Stationary Domains in the Casposo Low Sulfidation Epithermal Mineralization System. Grey dot lines define the VLT domain and the magenta line define the MQV domain figures 14.2, 14.3 and 14.4 shows the 3D stationary domains modeled for Manantiales, Julieta, Mercado and B-Vein.
Figure 14.1 Stationary Domains (Cross Section view) AuEq in ppm.
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Figure 14.2 Manantiales (left) and Julieta (right) mineralisation domains (plan view)
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Figure 14.3 Mercado mineralization domains (plan view).
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Figure 14.4 B-Vein domain (Plan View).
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Composites are the information that will be used in the estimation process and statistics are performed to all the units considered. Table 14.4 shows the codes defined for the Stationary Domains for the four deposits and the Table 14.5 are the statistics performed.
Geological and Estimation Domains
The geological domains were developed based on the interpretation of the AGL geology team for each deposit. Detailed logging was performed and compiled to define the main geological units which are the main mineralized structure composed of veins or hydrothermal breccias that were coded and interpreted in every cross section. An envelope of waste rock or in some cases low grade mineralization was interpreted to constrain the main geological unit that bearing gold and silver mineralization.
To define the Estimation Domains, we relied on the geological domains as long as the structural continuity was present. Parallel, secondary or tensional structures, define different geological domains and consequently different estimation domains.
In these types of deposits, it is typical to find parallel or tensional structures in an arrangement that is known as extensional jogs or bends.
Explicit domains were defined and the main mineralized estimation domain that was called Massive Quartz Vein [MQV], outer domains were identified as Veinlet [VLT] alluding to waste and in some cases low grade estimation domain and geologically present veinlets described in the log and in some cases when the mineralization style was not described the gold and silver grade can be used to define the outer domain. Only in the case of Manantiales deposit was another domain defined as breccia [BX] identified, whereby the estimation domains formed by the tectonic breccia in both hanging wall and footwall rocks.
3D Estimation: A typical process of 3D estimation was performed in every project. Volume is defined based on the drill holes intersections for both mineralized or waste geological domain, which will be used as Estimation Domain as long as the structural 3D continuity was verified. Sampling was transformed to regular composite and used to develop the geostatistical estimation.
Domain Coding: Compositing of the drill hole assay data was carried out using the run length method, that is defined according to the features of the population analyzed. The process is explained in more detail in section 14.7. The method is controlled by the unique numeric coding within the MRE database.
Bulk Density: A comprehensive program of systematic bulk density measurement was implemented and developed by AGL, and Bulk density, a compilation of 310 samples was provided detailed by rock type and was assigned an average value for each one, were calculated using accumulated and average values which show coherent values.
For the MRE, 2.5 ton/m3 was assumed based on the information provided and defined by the mine planning department. As the mineralization styles are mainly bearing in veins, hydrothermal breccias, stockworks and veinlets, it is recommended to perform intensified measurements in the mineralized units.
Currently, the amount of information that was collected in waste units is sufficient. However, the QP recommends continuing with this program and focusing on intensifying the measurements in mineralized units rather than waste rocks. Only 7 measurements were taken in veins or any other type of mineralized rock and the author agreed with the use of a constant value of 2.5 ton/m3 for all rock types.
Table 14.3: Assigned Bulk density.
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Mining Depletion
The project has been subject to both open pit and underground mining. Historic mining voids have been precisely quantified. Recent surface surveys undertaken by AGL have provided for all the deposits. The resulting wireframe of open pit voids is considered a reasonable representation of the base of surface mined volumes. The block models were properly built and blocks were created above the surface and declared as air.
Underground mining voids have been declared as mined-out material. For these voids, underground sampling and 3D tunnel wireframes were used to define the area exploited in each vein area.
Exploratory Data Analysis and Outliers
Complete global statistics of composite tabulations of Au, Ag on the MQV, BX and VLT Stationary Domains are presented. Tables within this section present the relevant statistics for each deposit and their respective domains.
Raw statistics for the calculated regularized 0.5 m composite are shown in Table 14.5.
Table 14.4: Stationary Domains and Codes for Manantiales, Julieta, Mercado and B-Vein Deposits.
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Table 14.5: Calculated Regularized composite at 0.5m stats.
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The generally high variance characteristics and material outliers within the composite's distribution indicates the need to limit high-grade values.
Outliers can be addressed using the following actions to limit their influence:
- Thresholds are detected and defined using lognormal probability plot, then its consistency of the definition is checked in the table calculating the relative differences between composites, when the relative difference is greater than 5% it could be possible to consider as an outlier. Both definitions must be geologically consistent and coherent and relevant experience in this matter is needed to define the threshold in a relevant stationary domain.
- Capping means all the composites major or equal to the threshold defined will be cutting and be replaced for this value. This action is not performed for the Casposo deposits because the metal content involved can be seriously affected due to the nature of this type of deposit's high grade variability and less geological continuity.
- Rather than capping, a high yield restriction is performed and is defined in the kriging plans. This means the treatment of the grades above the threshold will be restricted to an inner and smaller ellipsoid which define a very restricted and small influence, into the main search that were defined in every estimation pass and only when the samples above the top-cut or threshold is in this smaller search they will be used to estimate a block. If the outliers are out of the small and inner search never will be used to estimate a block.
Table 8-5 exhibits the threshold defined in the Stationary Domains. All distributions were analyzed and the defined thresholds were applied in the estimation plans.
Table 14.6: Outliers Definition for deposits and Stationary Domains.
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The main Massive Quartz Vein (MQV) domains exhibit grade ranges and variabilities considered large for robust linear interpolation. Visual inspection clearly shows the domains consist of mineralized and non-mineralized regions. Minor structures were estimated considering a linear interpolation, although the amount of information can be small, it is enough to develop the process.
Spatial Variability
One of the main parameters to define in a resource estimation is the spatial variability and the definition of a valid function to solve the Kriging equations. Variograms provide the information to solve an equation system with a unique and valid solution.
On the other hand, for this type of deposits a proper definition of anisotropy or the way that grades are distributed in the space is key to ensure an accurate process of estimation. In the early days and due to the limitation of the estimation software was usual to use fixed directions of the search ellipsoid but now is possible to use some routines to mimic the spatial distribution of geological variables like grades called local variable anisotropy that are fully conditioned by geological constrains. In all the Casposo Deposits was used a routine of variable ellipsoid to mimic the 3D distribution of grades and avoid some artifacts.
3D Variograms were performed using operational sampling to define a function to be applied in the deposits. The aim of production channels was to obtain information about the shortest distances rather than the longest distances. A semi-empirical model is provided to use in the estimation process and provide a coherent solution related to the optimal grid drilling.
Table 14.7: Semi-variogram defined as a semi-empirical model.
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Local Variable Anisotropy is an important feature of a geological domain and therefore for the stationary domain, it is important to know which are the directions of best continuity of mineralization called anisotropy. It is usual to define the local variable anisotropy to mimic the continuity of relevant geological features. In that way, was build an Anisotropy field based on the geological and stationary domains characteristics in specific the 3D orientation. Vulcan can build an Anisotropy Field based on surfaces and the information of this surface was recorded in the variables defined as bearing, plunge and dip.
Geological information is the base in the case of Epithermal Low Sulfidation deposits because they are structurally controlled and it is normal to follow a tabular shape of the ore bodies.
Cut-Off Grades and other parameters
Mineral Resources
Reasonable Prospect Assessment
The project is located on Mining Leases granted and has been historically mined. Grades and geometry are amenable to open pit and underground mining. The current (April 2024) Au price is ~US$2,250 per ounce and given probable credits from Ag, an average positive revenue per tonne (after recoveries) would be achievable. Therefore, there is no apparent reason the Casposo Au-Ag deposits could not be mined economically.
The reported open pit MRE has been confined above an optimisation shell and underground stopes modelled on the criteria tabulated in Table 14.12 and Table 14.13. The shell selected for a base of reasonable expectations for reporting the MRE assumed a gold price of USD $2,000/ounce and a silver price of USD $20/ounce.
Table 14.13: Parameters used in the optimisation process.
| Mining | Cost | ||||||||||
| Type | Cut-Off Grade | Dilution | Recovery | Slope | Density | Mining | Procesing | G&A | Selling | Operating | Cash |
| AuEq ppm | % | % | ° | ton/m3 | USD/ton | USD/ton | USD/ton | USD/ton | USD/ton | USD/ton | |
| Open Pit | 1.5 | - | 95 | 50 | 2.5 | 6 | 65 | 15 | 38.7 | 71 | 124.7 |
| Underground | 2.0 | 15 | 93 | 40/140 | 2.5 | 60 | 65 | 15 | 38.7 | 125 | 178.7 |
| Stockpile * | 1.0 | - | - | - | 1.8 | 1.5 | 45 | 10 | 38.7 | 46.5 | 95.2 |
* only variable costs was considered
Other parameters considered in the underground optimization are as follow:
- Distance between levels: 15 m [Bench 11 m, Drift 4 m]
- Minimum and maximum width: Bench 2.08 to 6 and drift 4 to 6
Minimum and maximum dip: Bench 40° and drift 140°
Metallurgical Recoveries were used according to the information obtained on the deposit to optimize the open pit and underground method. Table 14.13 illustrates the recoveries in each deposit.
Table 14.14: Recoveries used in the optimisation process.
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Stockpile optimization uses nearly the same parameters as open pit optimization. The key differences lie in the mining and general administrative costs, that were considered as variable costs.
Mineral Reserves
No Mineral Reserve were estimated.
Mining and Metallurgical Methods and Parameters
No mining methods were defined and metallurgical methods and parameters were assumed only to develop a reasonable prospect for economic extraction.
About Austral Gold
Austral Gold is a growing gold and silver mining producer building a portfolio of quality assets in the Americas. Austral continues to lay the foundation for its growth strategy by advancing its attractive portfolio of producing and exploration assets. For more information, please visit the Company's website at www.australgold.com.
Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.
Release approved by the Chief Executive Officer of Austral Gold, Stabro Kasaneva.
For additional information please contact:
Stabro Kasaneva
Chief Executive Officer
Austral Gold Limited
stabro.kasaneva@australgold.com
+56 9 9822 3563
Jose Bordogna
Chief Financial Officer
Austral Gold Limited
jose.bordogna@australgold.com
+61 466 892 307
Forward-Looking Statements
Statements in this news release that are not historical facts are forward-looking statements. Forward-Looking statements are statements that are not historical, and consist primarily of projections - statements regarding future plans, expectations and developments. Words such as "expects", "intends", "plans", "may", "could", "potential", "should", "anticipates", "likely", "believes" and words of similar import tend to identify forward- looking statements. Forward-Looking statements in this news release include Austral continues to lay the foundation for its growth strategy by advancing its attractive portfolio of producing and exploration assets.
All of these forward-looking statements are subject to a variety of known and unknown risks, uncertainties and other factors that could cause actual events or results to differ from those expressed or implied, including, without limitation, uncertainty of exploration programs, development plans and cost estimates, commodity price fluctuations; political or economic instability and regulatory changes; currency fluctuations, the state of the capital markets especially in light of the effects of the novel coronavirus, uncertainty in the measurement of mineral resources and reserves and other risks and hazards related to the exploration of a mineral property, and the availability of capital. You are cautioned that the foregoing list is not exhaustive of all factors and assumptions which may have been used. Austral cannot assure you that actual events, performance or results will be consistent with these forward-looking statements, and management's assumptions may prove to be incorrect. Austral's forward-looking statements reflect current expectations regarding future events and operating performance and speak only as of the date hereof and Austral does not assume any obligation to update forward-looking statements if circumstances or management's beliefs, expectations or opinions should change other than as required by applicable law. For the reasons set forth above, you should not place undue reliance on forward-looking statements.
JORC Code, 2012 Edition - Table 1 report
Section 1 Sampling Techniques and Data
(Criteria in this section apply to all succeeding sections.)
| Criteria | JORC Code explanation | Commentary |
| Sampling techniques |
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| Drilling techniques |
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Drill sample recovery |
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| Logging |
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| Sub-sampling techniques and sample preparation |
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Quality of assay data and laboratory tests |
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AGL utilized two mineral standards for the drilling:
For the Austral Gold infill drilling, diamond core, and Channel Sampling analysis were conducted for the results using the standards and blanks. Accuracy is monitored by certified standards which have an accepted value plus 2 standard deviations and additionally precision is monitored in a percentilerelative variation range within 2 standard deviations.
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| Verification of sampling and assaying |
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| Location of data points |
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| Data spacing and distribution |
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| Orientation of data in relation to geological structure |
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| Sample security |
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Audits or reviews |
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Section 2 Reporting of Exploration Results
(Criteria listed in the preceding section also apply to this section.)
| Criteria | JORC Code explanation | Commentary |
| Mineral tenement and land tenure status |
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File No. Name Date Area (ha) Notes Total (25 mining rights) 48,611.8
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| Exploration done by other parties |
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| Geology |
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Drill hole Information |
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| Data aggregation methods |
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Relationship between mineralisation widths and intercept lengths |
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| Diagrams |
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| Balanced reporting |
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Other substantive exploration data |
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Further work |
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Section 3 Estimation and Reporting of Mineral Resources
(Criteria listed in section 1, and where relevant in section 2, also apply to this section.)
| Criteria | JORC Code explanation | Commentary |
| Database integrity |
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| Site visits |
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| Geological interpretation |
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Dimensions |
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| Estimation and modelling techniques |
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| Moisture |
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Cut-off parameters |
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Mining factors or assumptions |
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Metallurgical factors or assumptions |
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Environmen- tal factors or assumptions |
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Bulk density |
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| Classification |
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Audits or reviews |
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Discussion of relative accuracy/ confidence |
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To view the source version of this press release, please visit https://www.newsfilecorp.com/release/217417
SOURCE: Austral Gold Limited
