Arena Minerals Announces Maiden 560,000 Tonne Lithium Carbonate Equivalent Brine Resource Estimate at Sal de la Puna Project

TORONTO, Oct. 19, 2021 - Arena Minerals Inc. ("Arena" or the "Company") (TSX-V: AN) is pleased to announce results of the maiden Mineral Resource Estimate ("MRE") conducted on its Sal de la Puna Project ("SDLP Project") located in the Pastos Grandes basin within Salta province, Argentina. The MRE was completed by Hydrominex Geoscience (Australia) and Tuareg Geological Services SRL (Argentina).

All reported mineral resources occur within a surface area of 690 hectares contained within the Almafuerte block, representing 6.3% of Arena's holdings in the basin. The MRE comprises an Inferred Mineral Resource of 230,000,000 cubic metres ("m3") of brine at an average lithium grade of 460 mg/l, for a total of 106,000 tonnes of lithium metal. The MRE equates to a contained 560,000 tonnes of lithium carbonate equivalent ("LCE"). The MRE extends down to a depth of 500 metres below surface and remains open at depth and on strike north towards the Graciela block and other properties owned by the Company.

Commenting on these results, Will Randall, President and CEO of Arena, stated, "This maiden resource estimate for the SDLP Project establishes it as one of the leading brine resources strategically situated in the coveted Pastos Grandes basin. The estimate offers an excellent platform to build out the resource potential given it only covers a small portion of our holdings in the basin. We believe the project has the potential to host significantly more lithium providing a solid foundation to further develop our business model with the ultimate goal of producing low-cost lithium products."

Table 1: Sal de la Puna Project Almafuerte Mineral Resource Estimate (effective as of September 9, 2021)

SDLP project Inferred lithium resource

SDLP project Inferred lithium carbonate equivalent (LCE) resource

1 Cut-off grade for brine used to calculate the resource was 0 milligrams per liter (no-cut off).
2 Tonnages are rounded to the nearest thousand.
3 Li Equivalency: each tonne of Li is equivalent to 5.3228 tonnes of Li2CO3.
4 The reader is cautioned that mineral resources are not mineral reserves and do not have demonstrated economic viability.
5 The estimate of Mineral Resources may be materially affected by environmental, permitting, legal, title, taxation, socio-political, marketing, or other relevant issues. The Inferred Mineral Resource in this estimate has a lower level of confidence and must not be converted to a Mineral Reserve. It is reasonably expected that the Inferred Mineral Resource could be upgraded to an Indicated Mineral Resource with continued exploration.
6. The Mineral Resource in this news release were estimated in accordance with the Canadian Institute of Mining, Metallurgy and Petroleum (CIM), CIM Standards on Mineral Resources and Reserves, Definitions (2014) and Best Practices Guidelines (2019) prepared by the CIM Standing Committee on Reserve Definitions and adopted by the CIM Council.

Estimation Methodology

An initial MRE has been defined in the Almafuerte block in the south of the Pastos Grandes salar based on results from drilling three holes. The lithium, potassium, magnesium and boron concentrations were estimated by Ordinary Kriging (OK). The block rock type composition was estimated using an inverse distance indicator model. These values were then weighted by the assumed porosity for each sediment type in order to assign a porosity to each block. All estimates were carried out using Micromine software.

Basin Boundaries

The resource estimate was developed by building a geological model with the results from SDLP drill holes and evaluating the publicly available information from Millennial Lithium and Lithium LSC further to the north.

A 3D wireframe solid was constructed in order to constrain the estimates. The edge of the basin sediments at surface was defined using topography and satellite imagery. The dip orientation of the faults on the edges of the basin is unknown but drilling near the basin edge to the north of the Almafuerte licence area indicates that the boundaries must be very steep. The thickness of the basin sediments is also unknown as none of the drill holes in the basin have reached the basement. The deepest drill hole in the whole basin has been drilled in the Almafuerte block and reaches a depth of 653 m. In order to model the sides of the basin the surface boundary was contracted by 100 m (into the salar) and projected 500 m downward.

Lithological Domains

The basin sediments are composed of layers of halite, gravel, sand, clay and silt. The sediment type does not appear to have any relationship to the brine grades however it has a strong influence on the downhole gamma readings.

Broadly speaking, the basin can be split into:

• Unit 1 - upper halite dominant zone; and
• Unit 2 - lower sand and interbedded finer clastic dominated zone. The contact nominally dips around 5˚ towards the east.

There is a large difference in porosity on either side of the Unit 1/Unit 2 contact. The contact was therefore treated as a hard boundary for the purposes of estimating. The surface created representing this contact was used to split the basin wireframe into two zones.

The resource model extents are controlled by the drilling information and geological interpretation. Because the Almafuerte block appears to straddle a faulted contact between salar sediments and older pre-salar Tertiary sediments (to the east) the interpreted fault is used to split sediments hosting brine from and barren non-porous rocks.

The elevation data from the Shuttle Radar Topographic Mission (SRTM) was downloaded and the collar elevations of the five drill holes used in the estimate were all within 2 m of the SRTM elevation data. The upper surface of the block model is the topography less a constant depth of 10 m, representing the depth of the water table below surface.

Assayed Intervals Used for Estimation

Three holes were drilled in the Almafuerte block. An additional 23 drill holes have been drilled to the north of the Almafuerte block on blocks owned by another company. The collar locations, logging and brine assay results of these additional drill holes are available in the public domain.

For the purposes of estimating the brine concentrations in the Almafuerte block, data from the three SDLP drill holes was combined with data from the southernmost two drill holes from the neighbouring block to the north. It was considered the inclusion of these data is likely to improve the estimate and information from the adjacent property was considered to have been collected in a reasonable manner, overseen by reputable companies, although it was not independent verified by the QP.

Brine assays were taken with fixed lengths, with some variability in the fixed length and distance between samples. For this reason, the brine assay values were treated as point data and were not composited prior to estimation. There are also large intervals in the middle of drill holes that lack brine assays, due to problems in recovering a brine sample during drilling.

It is to note that the brine sampling in drill hole PP0319, which is the northernmost SDLP drill holes, was completed after the well was installed and consequently was sampled in a different way. The range in grades is significantly smaller in this hole, compared to other holes.

Specific Yield Porosity

Specific yield data for the project was collected by direct measurement in-situ using a Borehole Magnetic Resonance (BMR) downhole logging geophysical tool. The BMR technology was developed in the oil industry and is increasingly used in groundwater and salt lake projects. The geophysical data collected in test production hole 3 was compared with data from the more limited geophysical logs collected in holes 1 and 2 and the geological logging to define the two geological units used for the resource estimation.

The porosity is expected to vary according to the sediment type, with lower porosities expected in finer grained sediments and evaporitic sediments. Down hole specific yield porosity data was only available from one drill hole, PP0319 (profiled with the BMR tool), and this data displays a more complicated down hole variation than was reflected by the geologically logged sediment type. It was therefore decided to use assumed specific yield porosities for each sediment type, based on extensive knowledge of salt lakes in Argentina, determined by laboratory test work, from similar sediments in a similar salar setting to the SDLP.

An inverse distance indicator model was created to assign these values to the block model. This involved compositing the geological logging to 4 m intervals and creating a column for each sediment type. The value 1 was assigned to the column corresponding to the logged sediment type while all other columns were assigned a zero. These values were then interpolated into the block model using an inverse distance method. The Unit 1 and 2 contact was treated as a hard boundary. The specific yield porosities were then calculated by taking the weighted average porosity for each sediment type. The average specific yield (drainable porosity) for the estimate was 6.25%.

Variogram Models and Search Criteria

Variography was carried out for the brine assays using all drill hole data from the basin, including data to the north of Almafuerte. The variograms generated were reasonably poorly structured owing to the widely and irregularly spaced data, and variable continuity of grades. Despite this, the variogram models showed longer ranges along the north-south long axis of the salt lake and shorter ranges across the east-west width of the salt lake. The shortest axis was vertical. This matches the expected relative anisotropy.

The estimate was conducted with three passes using expanding distances. Search criteria used for the brine assay OK estimate ranged from 2000 to 7000 m in the lateral dimensions and 100 to 300 m in the vertical.

Block Model

The drill holes in Almafuerte are positioned around 1.5 km apart. A block model was created using blocks sized 500x500x20 m (E, N, RL respectively). The plan dimensions were chosen as they are around a third of the drill hole spacing and the shorter vertical dimension was chosen to reflect downhole data spacing. Coordinates donate block centroid positions and are recorded in UTM WGS 84 Zone 19 (Southern Hemisphere). Discretisation was set to 5x5x5 (E, N, RL respectively).

The wireframes representing upper halite dominant and lower sand dominant zones were used to flag the block model. Sub-blocking was allowed, with the minimum dimensions of 250m x 250m x 10m (East x North x RL respectively). Blocks outside the salt lake were deleted. The proportion of the block below the topographic surface was assigned to the block model using a block factor. The proportion of the block inside the Almafuerte property was also assigned. Reported estimates must be weighted by proportion below topography multiplied by proportion in properties.

Reported estimate

The final block model was reviewed visually and it was concluded that the block model fairly represents the grades observed in the drill holes.

The entire estimate is classified as Inferred due to the relatively large distances between drill holes and the lack of good geological and grade continuity between drill holes. The relatively low variability of brine assays adds some confidence to the estimates.

The estimate can be improved by additional drilling to improve understanding of the controls on geological and grade continuity as well as better information on the depth of the basin and the contacts with the rocks to the east and west of the salt lake sediments.

Qualified Person

The scientific and technical information in this news release was prepared in accordance with the standards of the Canadian Institute of Mining, Metallurgy and Petroleum and National Instrument 43-101 - Standards of Disclosure for Mineral Projects ("NI 43-101"). It was reviewed, verified and compiled by Murray Brooker (M.Sc.), a Member of the Australian Institute of Geoscientists (AIG) and the International Association of Hydrogeologists (IAH), who is the Qualified Persons for the purpose of NI 43-101. Mr Brooker is an employee of Hydrominex Geoscience Pty Ltd and an independent consultant to Arena Minerals.

The resource is classified according to the CIM "Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines" dated November 29th, 2019 and CIM "Definition Standards for Mineral Resources and Mineral Reserves" dated May 10th, 2014. An NI 43-101 technical report disclosing the Sal de la Puna Project MRE will be filed on SEDAR within 45 days. Hydrominex Geoscience believes the SDLP Project has the potential for future economic extraction.

About Arena Minerals Inc.

Arena owns 65% of the Sal de la Puna Project covering approximately 11,000 hectares of the Pastos Grandes basin located in Salta, Argentina. The claims are highly prospective and share the basin with two advanced lithium brine projects. In addition to Sal de la Puna, the Company owns the Antofalla lithium brine project in Argentina, consisting of four claims covering a total of 6,000 hectares of the central portion of Salar de Antofalla, located immediately south of Albemarle Corporation's Antofalla project. Arena has developed a proprietary brine processing technology using brine type reagents derived from the Antofalla project with the objective of producing more competitive battery grade lithium products.

Arena also owns 80 percent of the Atacama Copper property within the Antofagasta region of Chile, and 5.8 million shares of Astra Exploration. The projects are at low altitudes, within producing mining camps in infrastructure-rich areas, located in the heart of Chile's premier copper mining district.

For more information regarding the Company, its management, expertise, and projects, please visit www.arenaminerals.com. An email registration allowing subscribers to directly receive news and updates is also available on the website.

The technical information contained in this news release has been reviewed and approved by William Randall, P.Geo, who is a Qualified Person as defined under NI 43-101. Mr. Randall is a director and is the Chief Executive Officer and President of Arena.

For more information, contact William Randall, President and CEO, at +1-416-818-8711 or Simon Marcotte, Corporate Development, at +1-647-801-7273 or smarcotte@arenaminerals.com.

On behalf of the Board of Directors of: Arena Minerals Inc.

William Randall, President and CEO

Cautionary Note Regarding Accuracy and Forward-Looking Information

This news release may contain forward-looking information within the meaning of applicable Canadian securities legislation. Forward-looking information includes, but is not limited to, statements, projections and estimates relating to the future development of any of the Company's properties, the anticipating timing with respect to private placement financings, the ability of the Company to complete private placement financings, results of the exploration program, future financial or operating performance of the Company, its subsidiaries and its projects, the development of and the anticipated timing with respect to the Atacama project in Chile, the Antofalla, Hombre Muerto or Pocitos Projects in Argentina , and the Company's ability to obtain financing. Generally, forward-looking information can be identified by the use of forward-looking terminology such as "plans", "expects" or "does not expect", "is expected", "budget", "scheduled", "estimates", "forecasts", "intends", "anticipates" or "does not anticipate", or "believes", or variations of such words and phrases or state that certain actions, events or results "may", "could", "would", "might" or "will be taken", "occur" or "be achieved". The statements made herein are based on current expectations and assumptions that are subject to risks and uncertainties. Actual results could differ materially because of factors discussed in the management discussion and analysis section of the Company's interim and most recent annual financial statement or other reports and filings with the TSX Venture Exchange and applicable Canadian securities regulations. Estimates underlying the results set out in this news release arise from work conducted by the previous owners and the Company. Forward-looking information is subject to known and unknown risks, uncertainties and other factors that may cause the actual results, level of activity, performance or achievements of the Company to be materially different from those expressed or implied by such forward-looking information, including but not limited to: general business, economic, competitive, geopolitical and social uncertainties; the actual results of current exploration activities; other risks of the mining industry and the risks described in the annual information form of the Company. Although the Company has attempted to identify important factors that could cause actual results to differ materially from those contained in forward-looking information, there may be other factors that cause results not to be as anticipated, estimated or intended. There can be no assurance that such information will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking information. Arena Minerals does not undertake to update any forward-looking information, except in accordance with applicable securities laws.

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accept responsibility for the adequacy or accuracy of this release.