San Marcial Area

VRIFY Tour of San Marcial and Plomosas Mine Areas

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Resource Growth Opportunity

• Modern data modelling combined with new geological knowledge supports the ongoing exploration drilling program
• Delineation of high-grade zones in bulk mineable style silver deposits

The 1,250-hectare San Marcial Area is located 98 kilometres southeast of Mazatlán, in the state of Sinaloa, Mexico, and 5 kilometres south of the Company’s Plomosas Mine Area.

The San Marcial Area, situated within the San Marcial Property, contains a significant silver resource (as outlined by the green line on the Geological Map), indicating potential for future mine development. The potential of the San Marcial Property was enhanced by the discovery of additional silver mineralization at the SE Area in August 2022 (101 m at 308 g/t Ag, including 17 m at 414 g/t Ag).

The San Marcial Property lies at the intersection of a major crustal E-W structure with an N-NW trending fault within the Rosario Mining District, located on the southwestern edge of the Sierra Madre Occidental (SMO). The San Marcial deposit is a well-preserved Ag-rich, high-grade epithermal hydrothermal breccia which was developed during the Oligocene extension of the SMO. The breccia is structurally and lithologically controlled by NW-SE crustal faults dipping to the east, and an Oligocene volcanoclastic sequence. The current NI 43-101  footprint represents only 25% of the area defined by extensive chargeability anomalies, where the recent geological exploration has defined potential similar geological settings with indications of intrusive-epithermal related silver gold exploration targets.

Chargeability Geophiscal Map (Red) – NI 43-101 Resource (Green Outline) – Targets (White)

In March 2023, GR Silver announced an updated NI 43-101 mineral resource estimate for the Plomosas Project, incorporating the San Marcial, Plomosas Mine and San Juan-La Colorada Areas. Full details are contained in the 2023 Technical Report.

The San Marcial deposit remains open along strike and at depth. The following royalty interest and purchase rights are related to the San Marcial Property: 0.75% NSR to EMX Royalty Corporation, with the ability to purchase back this royalty in full for US$1.25M, and a 3.0% net production royalty to Met-Sin Industriales S.A. de C.V., with the opportunity to purchase back this latter royalty in full or part for US$0.6M per each 1%.

Regional Geology

The geology of the San Marcial Area can be subdivided into two distinct underlying rock types. Firstly, the basement consists of undeformed late Jurassic volcaniclastic rocks. Secondly, these basement rocks are overlain by Early to Late Oligocene felsic ignimbrites, intermediate lavas, and occasional basaltic layers, separated by an angular unconformity. Several diorite porphyry bodies of Oligocene age intrude the San Marcial Area stratigraphy. Within the Oligocene volcanic sequence itself, another angular unconformity delineates two distinct eruptive phases, dated at 30–28 million years ago (Ma) and 28–26 Ma, respectively. The San Marcial Area silver exploration targets are hosted along a NW-trending crustal fault with a 60° NE dip, near the Jurassic – Oligocene prospective unconformity, which has been identified along a 1.5-kilometre length and almost 600 m down dip, delineating an elongate, tabular structure.

The San Marcial resource area hosts a series of telescoping high-grade Ag hydrothermal breccias, indicating that the system remains open at the deepest part of the deposit.

Mineralization styles at San Marcial

The main silver mineralized breccia was formed in three main phases:

1. Tectonic breccia at the fault hanging wall is characterized by a rock flour hematite matrix.
2. Ore breccia filling stage that contains the highest-grade silver values, located at the centre of the main structure; and
3. Post-crackle hydrothermal breccia at the footwall.

High-grade Ag values at the ore breccia filling stage are associated with:

1. telescoping of previous high Zn-Pb-Ag-Au epithermal vein systems;
2. disseminated acanthite filling open spaces on crackle calcite cement – part of a boiling event; and
3. thin calcite veins parallel to the main breccia within the host rock.

The San Marcial deposit alteration paragenetic signature is represented by a classic well preserved epithermal system as barite < fluorite > magnetite at the upper part of the system, and epidote < chlorite > tremolite < actinolite > tourmaline < apatite > titanite and muscovite at the lower part of the system.

Based on cross-cutting relationships, the three mineralization events occur within a short period. The mineralizing period is bracketed by deep hypabyssal dioritic porphyry intrusions (27.55 ± 0.75 Ma) and sin- or post-mineral rhyolitic dykes, which are shown to be younger due to cross-cutting relationships (26.41 ± 0.43 Ma). A later low-sulphidation Au vein-style mineralization, possibly related to felsic domes crosscut the San Marcial breccia at ~26 Ma.

While San Marcial is considered a silver deposit, the multi-phase mineralization creates a multi-commodity deposit with zinc and lead closely associated with the silver. In addition to the breccia and fault-hosted mineralization at San Marcial, epithermal gold mineralized vein and stockwork mineralization also exist, generally peripheral to the breccia-hosted silver mineralization.

Recent exploration by GR Silver Mining has identified additional occurrences of mineralization in the footwall below the San Marcial epithermal hydrothermal breccia.

Please click here to view our Discoveries Conference 2023 poster and Montoya-Lopera et al., 2025 long abstract presented at the SGA conference in Colorado, 2025.