Austral Gold Files Technical Report on Casposo and Addendum to ASX Release on 17 July 2024
Austral Gold Files Technical Report on
Casposo and Addendum to ASX Release on 17
July 2024
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:
1
.
Confidence in the Au and Ag estimate.
2
.
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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