• Partial results from first hole at El Cedro show gold mineralisation from surface.
  • CED001 - 61.35m @ 0.93g/t Au (from surface)
  • Including 42.15m @ 1.02 g/t from 19m.
• Target vein system intersected at 100m, as anticipated - assays pending.
• Drilling continues with planned hole depth of 500m.

London, United Kingdom--(Newsfile Corp. - September 15, 2026) - Orosur Mining Inc. (TSXV: OMI) (AIM: OMI) ("Orosur" or the "Company"), is pleased to announce an update on the progress of exploration activities at the Company's exploration project at Anzá in Colombia ("Anzá" or the "Project").

Anzá – Colombia
The Anzá Project in Colombia comprises a number of granted exploration titles and applications totalling roughly 530km², within the Mid-Cauca gold belt, west of Medellín.

These titles and applications are owned 100% by two Colombian companies, Minera Anzá, and Minera Monte Aguila, both wholly owned subsidiaries of the Company.

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

• Pepas - a shallow, high-grade ore body of gold mineralisation for which the Company has calculated a Mineral Resource Estimate ("MRE"), announced February 10^th 2026.
• APTA - a high-grade body of gold mineralisation that has to date seen approximately 40,000m of drilling since 2012, with drilling ongoing.
• El Cedro - a cluster of gold/copper porphyry intrusions and associated flanking hydrothermal systems in the south of the Project area at which drilling has just commenced with first results released today.

Figure 1. Anzá Project Location

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El Cedro
The El Cedro prospect lies to the south of the same integrated licence that hosts both Pepas and APTA and is roughly 4km south of the APTA base camp.

Work on the area began some years before Orosur's tenure, when Anglo American undertook reconnaissance mapping and sampling, identifying a highly prospective gold/copper porphyry system. An extensive area of anomalous soil geochemistry was delineated, as well as channel samples and rock chip samples with assays up to 10g/t Au and 2% Cu. No drilling was undertaken.

The prospect did not progress until late 2021, when the Company's previous JV partner MMA, re-entered the area to carry out mapping, sampling and ground geophysics that largely confirmed Anglo American's previous work and mapped two large dioritic intrusions and associated hydrothermal systems within a broad N-S structural corridor. No drilling was undertaken.

Figure 2. El Cedro location

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Post resumption of control of the Project in November 2024, the Company completed larger scale surface mapping programs, geochemical surveys and drone mounted magnetic surveys, focussing on identifying structures and hydrothermal features proximal to the intrusions that could have the potential for higher grade metal accumulations.

First drilling commenced at the El Cedro system on August 26^th, 2026.

The first drill hole at El Cedro (CED001) was positioned on the SE flank of the northern intrusion, close to the major structures that divide the northern and southern intrusions and are viewed as having controlled the emplacement of these systems and subsequent hydrothermal development.

The multiple objectives of CED001 were to test the flanks of the northern intrusion for potential intrusion related alteration that might produce wider scale mineralisation, and to intersect possible down dip extensions of multiple high grade vein systems that had been exposed in the adjacent creek system (Figure 3).

Figure 3. El Cedro, CED001 Plan

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Assays for the first 61.35m have been received, with the entire interval being mineralised, for a composite intersection of 61.35m at 0.93g/t Au. The final sample of this assayed interval returned 1.25g/t Au.

Table 1. Intersection

This zone also returned anomalous copper, however at levels deemed below economic significance.

Shallow Zone
The upper part of CED001 has intersected a complex sequence of strongly altered and locally brecciated rocks displaying evidence of multiple hydrothermal events.

Early logging has identified brecciated rocks containing porphyritic igneous and host-rock fragments affected by secondary biotite alteration and subsequent quartz-feldspar-related veining. More detailed logging subsequently recognized zones of secondary biotite, magnetite and pyrrhotite, locally associated with strong silicification and repeated millimeter-scale veining.

The geological relationships observed to date are interpreted to indicate a multi-stage intrusive-hydrothermal system, with an early high-temperature alteration event subsequently affected by repeated fracturing, brecciation, silicification and sulphide-bearing fluid flow.

Figure 4. a. CED001_15.00m Potassic alteration being cut by silicification with intense, brecciated texture; b. CED001_17.00m Fully obliterated rock, with pervasive alteration to quartz-sericite-clays (rich in silica-alumina). Relict phenocrysts of kaolinite-altered plagioclases remain in a silicified matrix.

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Vein Zone
CED001 was anticipated to intersect the vertical projection of the first of a set of high-grade surface veins and structures at 100m downhole (Figure 5).

Figure 5. Interpreted section, CED001

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At roughly 99m downhole, CED001 entered a wide zone of polymetallic veining, demonstrating strongly silicified rocks containing abundant quartz-carbonate-sulphide veins containing pyrrhotite, pyrite, galena, sphalerite and locally chalcopyrite, within a broader alteration halo.

Figure 6. CED001_99.00m Carbonate-pyrrhotite-pyrite veinlet cutting silicification and potassic alteration.

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Figure 7. CED001_99.15m Carbonate-pyrrhotite-pyrite veinlet cutting silicification and potassic alteration.

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Figure 8. CED001_108.5m polymetallic structure composed of galena, pyrite, sphalerite, and chalcopyrite. The zone is sheared and displays a brecciated texture.

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These deeper intervals display a notable increase in vein and veinlet density, being more closely comparable to the gold-bearing polymetallic veins observed at surface than to the alteration assemblage associated within the currently assayed upper interval.

Channel sampling of the surface veins upon which CED001 was targeted returned values of up to 8.83 g/t Au (Figure 5), however the veins interpreted to have been intersected in this current zone, were the lowest grade of those at surface, at less than 0.5g/t Au, suggesting that vein scale and tenor may increase substantially with depth.

Figure 9. Hand sample and outcrop photographs of mineralised structures identified at surface at El Cedro, with channel sample results from the site: CH101376 - 4.21 g/t Au; CH101377 - 8.83 g/t Au; CH101373 - 2.31 g/t Au.

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The vertical projection of the higher-grade surface veins are interpreted to be potentially intersected at various points deeper in the hole (Figure 5), however given the increased depth extrapolation, uncertainty increases substantially.

Samples from 61.3m to 86m have been submitted for assay this week, with results expected in the near term. Further samples, including those from the vein zone, should be submitted to the laboratory later this week.

CED001 is currently at 130m. The hole is planned to extend to 500m and is expected to be completed by the end of the month.

Summary
The Company considers these results from the first hole ever drilled on the prospect to be highly encouraging, as evidence of a substantial porphyry/hydrothermal mineralised system. Only one rig is currently dedicated to the El Cedro system, with two more holes planned to be drilled in different directions from the same pad once CED001 is complete. However, these plans may be reviewed as the hole progresses, and a more detailed geological picture develops.

Orosur CEO Brad George commented:
"Real grassroots discoveries have become very rare in modern times - and we possibly have two……so far. This is testament to the geological potential of the Anza Project and Colombia as an exploration destination, but mostly to the talent and dedication of the local team."

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

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 - El Cedro Prospect

Drill Hole Details - APTA prospect *
*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 and MAP-106 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

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 geological 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.

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Source: Orosur Mining Inc.