Oroco Increases South Zone Certainty at Santo Tomás
June 18, 2026 NEWS RELEASE
OROCO INCREASES SOUTH ZONE CERTAINTY AT SANTO TOMÁS
VANCOUVER, Canada, June 18, 2026 – Oroco Resource Corp. (TSX-V: OCO; OTCQB: ORRCF)
("Oroco" or the "Company") is pleased to report the second set of assay results from its Phase 2 resource
drilling program focused on the South Zone at its Sa nto Tomás copper project, Choix, Sinaloa, Mexico.
Results are reported for drill holes S025, S026, S028 and S029 and are consistent with the 2024 Technical
Report block model in the areas tested.
"Our Phase 2 drilling continues to confirm a compelling copper resource at Santo Tomas with
low capital intensity requirements. The results clearly support a near or at surface, low strip
resource as defined in the August 2024 Technical Report. The program is focused on increasing
resource certainty in the South Zone to support the mine plan and a Pre-Feasibility Study, and
that is what is being delivered," stated Oroco President, Ian Graham. "The elevated grades in
the area of the S018 drill pad further confirm early access development in the southwest part of
the South Zone and, most notably, S031 has provided evidence of mineralization that extends
beyond the inferred resource of the existing block model."
Highlights
• Hole S025, a near-vertical hole collared on the same pad as S024, returned intervals consistent with
the August 2024 Preliminary Economic Assessment block model (the “ PEA Block Model”) and
suggests stronger and thicker mineralization than was intersected in S024, including 84.94m at
0.29% Cu / 0.33% CuEq and 90m at 0.41% Cu / 0.53% CuEq.
• Hole S026 was drilled SSW from the same pad as S018 (see May 21, 2026 news release) and
returned 48.6m at 0.56% Cu / 0.67% CuEq, 59m at 0.2% Cu / 0.33% CuEq and 23.45m at
0.16% Cu / 0.24% CuEq. The higher-grade material was intersected in the shallower parts of the
hole.
• Hole S028 was drilled WSW from the same pad as S026 and tested the western limits of South
Zone mineralization against the PEA Block Model, returning 44.52m at 0.38% Cu / 0.46% CuEQ.
• Hole S029 is located 700m NNW of holes S026 and S028. The hole was drilled for infill purposes
and intersected mineralization from the sha llow alluvium-bedrock contact, including 58.76m at
0.35% Cu / 0.43% CuEq and 16.01 m at 0.29% Cu / 0.35% CuEq, reflecting very near surface
mineralization and reducing strip in this area compared to the block model.
Hole S031, which was drilled to the west off the same pad as hole 29, extended visual mineralization
beyond the inferred resource in the PEA Block Model (assays pending). The Company is awaiting
soluble copper assays for Hole S027 intercepts that returned oxide copper mineralization, and will be
reported once these are received and pass QA/QC review. Soluble copper assays for oxide copper
intercepts in additional holes, including drill holes S030 and S032, may also affect the sequencing of the
periodic release of drilling data.
The Company has mobilized a third rig to the project site. Twenty-two (22) drill holes totaling 6,709 m of
the Phase 2 program have been completed, and access and pad development for the ongoing program are
being accelerated.
Phase 2 Program Overview
Phase 2 is designed primarily to convert Inferred res ources to the Indicated resource classification in the
South Zone and to collect geotechnical, hydrogeological, and additional metallurgical data required for Pre-
Feasibility Study ("PFS") level mine-planning.
Drilling is also planned in the pillar area between th e North and South Zones and along the southeastern
edge of the North Zone pit shell. The PFS is targeted for release in Q2/Q3 2027.
Table 1: Phase 2 Drill Holes S025, S026, S028 and S029
Hole East
(m)
North
(m)
Elev.
(m)
Dip
(deg.)
Az.
(deg.) Objective / Comment
S025 778,914 2,975,038 677 -85 280
Same pad as S024. Infill drilling for block model
support. Higher molybdenum grades in the
deeper interval. Results consistent with PEA
Block Model
S026 778,867 2,974,901 674 -60 190
Drilled southwards off same pad as S018.
Tested western limits of the current PEA pit
shell. Notably higher Au grades near the top of
the hole. Ended in lower grade mineralization,
but above the 0.15% Cu cut off.
S028 778,867 2,974,901 674 -55 245
Drilled southwestwards off the same pad as
S018. As with S024 (May 21, 2026 news
release), it may have drilled above the main
mineralized horizon. Ended with elevated Cu
and Mo values suggesting deeper westward
mineralization.
S029 778,626 2,975,562 589 -55 95
Infill hole testing western limits: largely
consistent with the PEA Block Model. S031,
drilled to the west from same pad, intersected
visual mineralization outside of the current PEA
Block Model (assays pending)
Table 2: Significant Assay Results**
Hole
From
(m)
To
(m)
Length
(m) Cu% Mo% Au ppm Ag ppm Cu
Eq%
S025
37 121.94 84.94 0.29 0.005 0.014 1.65 0.33
131 221 90 0.41 0.022 0.01 2.38 0.53
S026
42 90.6 48.6 0.56 0.015 0.017 3.12 0.67
93 152 59 0.2 0.026 0.008 1.44 0.33
280 303.45 23.45 0.16 0.013 0.011 1.56 0.24
S028 44 88.52 44.52 0.38 0.013 0.01 1.83 0.46
S029
27 85.76 58.76 0.35 0.009 0.018 2.22 0.43
87.32 103.33 16.01 0.29 0.007 0.007 1.71 0.35
* CuEq (%) = [(Cu% × Cu recovery (variable) × Cu price) + (Mo% × Mo recovery (variable) × Mo price)
+ (Au g/t × Au recovery (variable) × Au price) + (Ag g/t × Ag recovery (variable) × Ag price)] ÷ (Cu price
× Cu recovery (variable)). Metal prices in US$/lb (Cu, Mo) and US$/oz (Au, Ag) See table 3. Metal
recoveries are grade based by individual assay in th e reported intervals and vary accordingly. In these
intervals Cu recovery ranges from 82-89%, Mo 58-60%, Au 30-85% and Ag 35-67%. Au and Ag recoveries
are dependent on Cu and Sulphur grades.
**Significant Intervals comprise intervals ≥ 10m of ≥ 0.15% Cu, but may include assay intervals of ≤ 4m
of ≥ 0.05% Cu. This continues the practice of signi ficant interval reporting applied during Phase 1,
including News Releases and the August 2024 PEA.
All intervals are down hole drill core lengths. True widths will be confirmed when Phase 2 results are
incorporated into the updated geological and r esource models. Where holes are drilled approximately
perpendicular to the interpreted structural attitude of the mineralization, core intervals are expected to
approximate true thickness.
Copper Equivalent (CuEq) Reporting
CuEq grades in this release are calculated using the variable metal recovery curves from Chapter 13 of the
Company’s August 2024 Technical Report (“Santo Tomás Copper Project, Sinaloa, Mexico — Technical
Report on a Preliminary Economic Assessment” (the “ PEA”), filed on SEDAR+ August 2024) and the
metal price deck in Table 3, reflecting 12-month traili ng average prices to April 30, 2026. This price deck
differs from that used in the PEA.
Copper equivalent grades in this release are not dir ectly comparable to CuEq grades reported in the
Company’s 2024 Indicated and Inferred Resource Summar y Table or in earlier drill-result news releases
prior to 2024, which used different metal price assumptions and CuEq methodologies. The Company has
recalculated the significant-intercept database for the full drill-hole dataset using the updated CuEq
calculation: the historical drilling results and the results for holes S022 to S024 have been updated in the
VRIFY drill-hole viewer and are available at VRIFY and via the Company’s website. Results from this
news release will be reflected in VRIFY in due course.
Table 3: Metal Prices Used for Phase 2 CuEq Calculations
Metal Cu Mo Au Ag
Price (rounded) US$5.00/lb US$25.75/lb US$4,070/oz US$56.50/oz
Actual trailing average US$5.05/lb US$25.74/lb US$4,070.20/oz US$56.40
Quality Assurance / Quality Control
Historical drilling data used in the current explora tion program and resource estim ate were subject to the
data verification procedures described in the Compa ny’s current Technical Report. Drill collar locations
are verified by differential GPS with checks agains t LiDAR data. Geological logging, core sampling,
sample preparation, analysis, and chain of custody are governed by QA/QC protocols that include the
insertion of certified reference standards, blanks, and duplicates. Samples are submitted to ALS Chemex
(Hermosillo, Mexico) for sample preparation; pulps are sent to ALS Canada Ltd. (Vancouver) for analysis.
Total copper, molybdenum, and silver are determin ed by ALS method ME-ICP61 (four-acid ICP-AES);
over-limit results use ore-grade assay methods. Gold is determined by ALS met hod Au-AA23 (30 g fire
assay with AAS finish).
Qualified Person
Andrew Ware, RM-SME, a Qualified Person as define d in NI 43-101 — Standards of Disclosure for
Mineral Projects, and a senior consulting geoscientist to the Company, has reviewed and approved the
technical disclosures in this news release. The Comp any adheres to CIM Best Practices Guidelines in
conducting, documenting, and reporting exploration activities.
About Santo Tomás
Santo Tomás is an advanced-stage porphyry copper project in Choix, Si naloa, Mexico. Oroco holds a net
87.0% interest in the 1,173-hect are Core Concessions and an 80% interest in surrounding concessions at
Santo Tomás. The Project was tested by historical drilling from 1968 to 1994 and by Oroco's Phase 1
program, which totaled 48,481 metres in 76 diamond drill holes and supported the revised Mineral Resource
Estimate (“MRE”) and updated PEA.
The August 2024 MRE, prepared by SRK Consulting (U.S.), Inc., outlined an Indicated Resource of 540.6
Mt at 0.33% Cu, 0.008% Mo, 0.028ppm Au and 2.1 ppm Ag and an Inferred Resource of 530.3 Mt at
0.31% Cu, 0.007% Mo, 0.023ppm Au and 1.9ppm Ag . The updated PEA, prepared by Ausenco
Engineering USA South Inc., contemplates a staged open-pit operation ramping from 60,000 t/d in Year 1
to 120,000 t/d by Year 8 over a 22.6-year life of mine, generating an after-tax NPV₈% of US$1.48 billion
and an after-tax IRR of 22.2%. Both studies are available at www.orocoresourcecorp.com and on SEDAR+
at www.sedarplus.ca. The PEA is preliminary in nature; see "Cautionary Note" below.
About Oroco Resource Corp.
Oroco Resource Corp. is a Vancouver-based mineral exploration and development company advancing the
Santo Tomás copper project in Sinaloa, Mexico.
For further information:
Ian Graham, President
Oroco Resource Corp.
Tel: 604-688-6200 | [email protected] | www.orocoresourcecorp.com
Cautionary Note Regarding Forward-Looking Information
This news release contains forward-looking inform ation within the meaning of applicable Canadian
securities legislation, including statements regardi ng: the Phase 2 drilling program and its objectives; the
consistency of drilling results with the 2024 Technical Report block m odel; the anticipated advancement
of the Santo Tomás Project toward a Pre-Feasibility Study and its targeted release in Q2/Q3 2027; planned
and ongoing drilling, access and pad development; pending assays and the anticipated release of additional
drilling data; the Company’s intention to update VRIF Y with additional drill results; and the anticipated
conversion of Inferred resources to the Indicated cat egory. Forward-looking information is based on
management’s current expectations and assumptions, including assumptions regarding continued access to
the project, contractor availability, assay laboratory turnaround times, geological continuity and commodity
prices. Such information is subject to known and unk nown risks, uncertainties, and other factors that may
cause actual results to differ materially from those expressed or implied, including drilling results,
geological and resource estimation uncertainty, comm odity price fluctuations, regulatory and permitting
risks, and general economic conditi ons. A Preliminary Economic Assessme nt is preliminary in nature,
includes Inferred Mineral Resources considered too sp eculative geologically to be categorized as Mineral
Reserves, and there is no certainty that results of th e PEA will be realized. Readers are cautioned not to
place undue reliance on forward-looking information. The Company does not undertake to update forward-
looking information, except as required by applicable securities law.
Neither the TSX Venture Exchange nor its Regula tion Services Provider accepts responsibility for the
adequacy or accuracy of this news release.