Pepas MRE drilling near completion

Drilling at El Pantano in Argentina hits mineral system

·    Assays for five holes from the Pepas resource drilling program, including:

o PEP067 - 83.7m @ 4.29g/t Au from surface

·    Resource modelling and NI43-101 report process under way

·    First holes from El Pantano drilling program confirm a low sulphidation epithermal mineral system - awaiting assays.

London, December 12^th, 2025. Orosur Mining Inc. ("Orosur" or the "Company") (TSXV/AIM:OMI), is pleased to announce an update on the progress of exploration activities at the Company's exploration projects at Anzá in Colombia ("Anzá) and El Pantano in Argentina ("El Pantano").

Anzá - Colombia

The Anzá Project in Colombia comprises a number of granted exploration titles and applications totalling roughly 330km², within the Mid-Cauca gold belt, west of the city of Medellin.

These titles and applications are owned by two Colombian companies, Minera Anzá, and Minera Monte Aguila, both of which are wholly owned subsidiaries of the Company. The latter of these was acquired by Orosur in November 2024 from the Company's previous JV partners, Newmont Mining and Agnico Eagle Mines.  Orosur thus owns 100% of the Anzá Project.

Since acquiring 100% control, the Company has focussed its attention on three prospects:

·    Pepas - a shallow, high-grade body of gold mineralisation that the Company is endeavouring to move to an initial Mineral Resource Estimate ('MRE') in the near term.

·    APTA - a high-grade body of gold mineralisation that has to date seen 38,000m of drilling, but is not yet sufficiently understood geologically to allow a MRE to be calculated.  The Company plans to undertake additional drilling at APTA in 2026, with the objective of advancing it toward an MRE.

·    El Cedro - a large gold porphyry system in the south of the Project area. The Company has completed a large soil sampling program and plans to undertake a maiden drill program here in early 2026.

Figure 1. Anzá Project

As announced on 14^th July 2025, the Company had taken the formal decision to commence infill drilling at its Pepas gold prospect at Anzá, with the objective of moving Pepas to a NI43-101 compliant Mineral Resource Estimate as quickly as possible.

The Company's external geological and resource consultants visited the Anza site at the start of November to carry out the necessary QAQC verification of drilling and sampling and to work with the Orosur geological team in the development of a new NI43-101 technical report for the Anza project, which will include a MRE for the Pepas Prospect.

One outcome of this visit was the recommendation by the consultants for an extension of the final stages of the MRE drill-out program, with several additional holes within and outside the Pepas deposit to define the boundaries of the current deposit envelope and obtain a better understanding of the size and controls of previously defined high-grade zones. 

Holes drilled outside the deposit envelope have returned the lower grade halo mineralisation as expected and have provided valuable information as to the nature of the some of the controlling structures of Pepas. The one hole of this current batch drilled inside the deposit envelope (PEP-067) returned a result of 83.7m @ 4.29g/t Au from surface.

Table 1. Latest drill Intercepts, Pepas Prospect

Figure 2.  Plan of holes

Figure 3. Section, PEP067

It is expected that the Pepas drill-out program will continue for the next few days and the resulting MRE and technical report can then be completed during January 2026.

Metallurgy

As part of the MRE process, a large diameter PQ drill hole was completed specifically to provide sufficient material for a comprehensive metallurgical testing program. These samples have been sent to the metallurgical testing facility of ALS Global in British Columbia, where the work is now well advanced. It is hoped this program may be completed by the end of the year and thus feed into the Technical Report and MRE.

Wider Exploration - Anza

The Company had previously announced that it had planned to undertake a detailed airborne magnetic survey over the EL Cedro and APTA prospects in December, as a tool to provide additional guidance for drilling in early 2026. The Company is engaging with contractors to commission the survey.

Mapping, sampling and trenching is also underway in the environs of the Pepas deposit, as part of an ongoing program to explore for extensions and/or repetitions of Pepas.  Once the current resource drilling program is completed in coming weeks, it is likely the rig will be shifted to targets being developed around Pepas.

El Pantano - Argentina

The El Pantano Project is an early-stage gold/silver exploration project in Santa Cruz province, southern Argentina.

The Project comprises approximately 550km² of contiguous granted licences in the prolific Deseado Massif of Santa Cruz Province, roughly 45km from Anglo Gold's Cerro Vanguardia mining camp and 90km SE of Newmont Mining's giant Cerro Negro mine.

El Pantano is subject to an Exploration & Joint Venture ("JV") agreement ("Agreement") with private Argentinean company Deseado Dorado S.A.S and its shareholders ("Deseado"), the details of which were announced on February 15^th 2022.

The Company currently owns 51% of El Pantano, having met its obligation to spend US$1m in exploration expenditure by February 2025. The Company is now in Phase 2 of the joint venture, whereby it may earn an additional 49% equity in the project (taking the Company to 100% ownership) by investing US$2m in the two years to February 2027.   Upon such an event, the original vendors would retain a 2% NSR royalty, 1% of which the Company could purchase for US$1m at its discretion.

Following several years of surface field work, the Company commenced the first phase of drilling ever undertaken within the project area in early November 2025.  Between 3,000-4,000m is planned across the breadth of the project area as a reconnaissance program designed to address a number of geological questions:

·    Test sources of geochemical anomalism

·    Assess a variety of Induced Polarisation responses

·    Intersect, if possible, mineralised structures indicative of the low sulphidation epithermal model being postulated at El Pantano

·    Gain understanding of the vertical variations in the system, especially in relation to the potential for fluid boiling.

In a general sense, the broad objective of the program is to determine if a mineral system is present at El Pantano, and if so, develop exploration plans for further work.

Figure 4.  El Pantano geology and geochemistry

Samples from the El Pantano project are sent to the preparation facility and fire assay laboratory of Alex Stewart Laboratories in Perito Moreno to be assayed for gold.  Pulps are then sent to the larger Alex Stewart facility in Mendoza for multi-element analysis.

To date, seven holes have been completed with samples from the first five submitted to the laboratory in Perito Moreno for fire assay gold analysis, to be followed by multi- element analysis, including silver, from the Mendoza facility.

Visually, several of the holes have intersected extremely encouraging structures showing textures and mineralogy consistent with what is seen in other low sulphidation epithermal systems in the region.  In particular, the presence of colloform banding in several intersected narrow veins is a key indicator often seen in the core of low sulphidation epithermal systems.

Preliminary interpretation would suggest that vein textures are indicative of lower temperatures, albeit with some examples of higher temperature overprinting.  This would suggest that current drilling is still higher in the system, above the boiling zone.  

Fig 5. Colloform banding, El Pantano

The Company is confident that it has achieved its general objective of proving the existence of a substantial mineral system. This is an extremely positive and unusual result for the first drilling program on a grass roots project. The challenge, however, is identifying where, within the mineral system, economic widths and grades may have been deposited.

Drilling is progressing faster than anticipated and thus it is planned that this program will be completed toward the end of January 2026.  Once complete, all new and historical data will be compiled as the key component to a targeting program that will develop the next phase of work.

Orosur CEO Brad George commented:

"Pepas is now in the final mile of its MRE process and the pieces are coming together for a January report.  In the meantime, we are lining up targets for when the rig is freed up later in December.  Drilling at El Pantano, as with any undrilled project, was high risk, but we have hit what we hoped to hit - a previously unknown mineral system.  Now we need to focus in, and given the scale of the system, that is a challenge….but a good challenge".

For further information, visit www.orosur.ca, follow on X @orosurm or please contact:

Orosur Mining Inc

Louis Castro, Chairman,

Brad George, CEO

[email protected]

Tel: +1 (778) 373-0100

SP Angel Corporate Finance LLP - Nomad & Joint Broker

Jeff Keating / Jen Clarke / Devik Mehta

Tel: +44 (0) 20 3470 0470

Turner Pope Investments (TPI) Ltd - Joint Broker

Andy Thacker/Guy McDougall
Tel: +44 (0)20 3657 0050

Flagstaff Communications and Investor Communications

Tim Thompson
Mark Edwards
Fergus Mellon

[email protected]

Tel: +44 (0)207 129 1474

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014 ('MAR') which has been incorporated into UK law by the European Union (Withdrawal) Act 2018. Upon the publication of this announcement via Regulatory Information Service ('RIS'), this inside information is now considered to be in the public domain.

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

Drill Hole Details - Pepas prospect 2022/2024 Programme*

Drill Hole Details, El Pantano Project 2025 onward

*  Coordinates WGS84, UTM Zone 18

About Orosur Mining Inc.

Orosur Mining Inc. (TSXV: OMI; AIM: OMI) is a minerals explorer and developer currently operating in Colombia and Argentina.

Qualified Persons Statement

The information in this news release was compiled, reviewed, verified and approved by Mr. Brad George, BSc Hons (Geology and Geophysics), MBA, Member of the Australian Institute of Geoscientists (MAIG), CEO of Orosur Mining Inc. and a qualified person as defined by National Instrument 43-101.

Orosur Mining Inc. staff follow standard operating and quality assurance procedures to ensure that sampling techniques and sample results meet international reporting standards.

Drill core is split in half over widths that vary between 0.3m and 2m, depending upon the geological domain. One half is kept on site in the Minera Anzá core storage facility in the case of the Anza Project, or on site in temporary racks in the case of the El Pantano Project, with the other sent for assay.

Industry standard QAQC protocols are put in place with approximately 10% of total submitted samples being blanks, repeats or Certified Reference Materials (CRMs).

Samples for holes PEP-001 to PEP-011 were sent to the Medellin preparation facility of ALS Colombia Ltd, and then to the ISO 9001 certified ALS Chemex laboratory in Lima, Peru.

Samples from PEP-012 onwards are sent to Medellin laboratory of Actlabs for preparation and fire assay, with some sample then sent to the Canadian Actlabs facility for multi element assay

Samples from the EL Pantano project are sent to the preparation facility and fire assay laboratory of Alex Stewart Laboratories in Perito Moreno to be assayed for gold.  Pulps are then sent to the larger Alex Stewart facility in Mendoza for multi-element analysis.

30 gram nominal weight samples are then subject to fire assay and AAS analysis for gold with gravimetric re-finish for overlimit assays of >5 g/t.  ICP-MS Ultra-Trace level multi-element four-acid digest analyses may also undertaken for such elements as silver, copper, lead and zinc, etc.

Gold intersections are reported using a lower cut-off of 0.3g/t Au over 3m.

Intersections are quoted as downhole thicknesses.  True thicknesses are unknown.

Forward Looking Statements

All statements, other than statements of historical fact, contained in this news release constitute "forward looking statements" within the meaning of applicable securities laws, including but not limited to the "safe harbour" provisions of the United States Private Securities Litigation Reform Act of 1995 and are based on expectations estimates and projections as of the date of this news release.

Forward-looking statements include, without limitation, the continuing focus on the Pepas prospect, the exploration plans in Colombia and the funding of those plans, and other events or conditions that may occur in the future. There can be no assurance that such statements will prove to be accurate. Actual results and future events could differ materially from those anticipated in such forward-looking statements. Such statements are subject to significant risks and uncertainties including, but not limited to, those described in the Section "Risks Factors" of the Company's MD&A for the year ended May 31, 2025. The Company's continuance as a going concern is dependent upon its ability to obtain adequate financing. This material uncertainty may cast significant doubt upon the Company's ability to realize its assets and discharge its liabilities in the normal course of business and accordingly the appropriateness of the use of accounting principles applicable to a going concern. The Company disclaims any intention or obligation to update or revise any forward-looking statements whether as a result of new information, future events and such forward-looking statements, except to the extent required by applicable law.