Plomosas Mine Area Summary
VRIFY Tour of San Marcial and Plomosas Mine Areas
Click the arrows icon below to view
Delineation Of New Silver Resources In A Past Producing Permitted Site
Historical plomosas underground mine area aerial view.
The Plomosas Mine Area (“Plomosas Property”) is located within 5 kilometres of GR Silver Mining’s San Marcial Area (“San Marcial Property”) in the Rosario Mining District, Sinaloa, potentially providing opportunities for the synergistic future development of both areas.
The Plomosas Property includes a past-producing silver–gold–lead–zinc (Ag-Au-Pb-Zn) underground mine (“Plomosas Mine”), which was operated by Grupo Mexico S.A. de C.V., within 8,515 hectares of mining concessions with numerous exploration targets. The Plomosas Mine is a historical underground mine site with existing permits and authorizations to operate future mining operations. The site has key infrastructure that includes a 100-person camp, and access to power and water
The combination of infrastructure and historical data, along with a new, recently completed geological model, indicates upside potential for resource expansion, future exploration and discoveries.
The Plomosas Property, together with the San Marcial Property, provides GR Silver Mining with control over 9,764 hectares, covering most of the Ag-Au-Pb-Zn mineralized zones in the eastern portion of the Rosario Mining District.
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, including the mineral resource estimate, are contained in the Technical Report.
Numbers are rounded
* AgEq = calculated from the metal prices and recoveries using the equation AgEq = ((Ag grade x Ag Price x Ag recovery) + (Au grade x Au price x Au recovery) + (Pb grade x Pb price x Pb recovery) + (Zn grade x Zn price x Zn recovery) + (Cu grade x Cu price x Cu recovery))/(Ag price x Ag recovery)
(1) Mineral Resources which are not Mineral Reserves, do not have demonstrated economic viability
(2) The estimate of Mineral Resources may be materially affected by environmental, permitting, legal, title, taxation, socio-political, marketing, or other relevant issues
(3) The Inferred Mineral Resource in this estimate has a lower level of confidence than that applied to an Indicated Mineral Resource and must not be converted to a Mineral Reserve. It is reasonably expected that the majority of the Inferred Mineral Resource could be upgraded to an Indicated Mineral Resource with continued exploration
(4) The Mineral Resources were estimated using the Canadian Institute of Mining, Metallurgy and Petroleum (CIM), CIM Standards on Mineral Resources and Reserves, Definitions and Guidelines prepared by the CIM Standing Committee on Reserve Definitions and adopted by the CIM Council
The following royalty interests and purchase rights are applicable to the Plomosas Property: 2% NSR to Royalty Streaming Mexico S.A. de C.V. with a buyback right on 1% NSR for US$1.0M, and a 1.75% – 3.5% net production and sales royalty to Industrial Minera México (a subsidiary of Grupo Mexico) based on the price of zinc.
Plomosas Mine Area Geology
The Plomosas Property is situated 98 kilometres southeast of Mazatlán in a straight line, or 198 kilometres by road, at the southwestern end of the Sierra Madre Occidental (SMO). The Plomosas deposit lies within an erosional window typical of the SMO due to regional extensional events (Ferrari et al., 2007, 2018, 2020; Montoya-Lopera et al., 2019, 2024).
The local basement is composed of non-deformed Late Jurassic volcaniclastic units and coeval felsic intrusions dated at 164-151 Ma. Early to Late Oligocene volcanic packages of silicic ignimbrites, intermediate lava flows, and occasional basaltic flows directly overlay the Jurassic basement, separated by an angular discordance. Several Oligocene diorite porphyry bodies and a few Miocene rhyolitic domes intrude the Plomosas stratigraphy. Within the Oligocene volcanic sequence, an angular discordance separates an early and a late period, dated at 32–28 Ma and 28–26 Ma, respectively (Montoya-Lopera et al., 2024).
The Plomosas mineralization has been described as a low-angle fault, Pb-Zn rich epithermal hydrothermal breccia striking NNW and dipping 45°-60°W that has been recognized over a length of more than a kilometre (Gonzalez-Partida et al., 2006; Montoya-Lopera et al., 2024).
The main mineralized zone has been identified over 150 m along strike and 700 m down dip, and is controlled by a low-angle, N-S oriented fault breccia.
Recent drilling and geological modelling have identified evidence of three epithermal mineralization events at Plomosas:
(1) the historically-rich galena-sphalerite event – represented by chalcopyrite, sphalerite, galena, quartz-chlorite-carbonate;
(2) high-grade Ag event – associated with chalcopyrite, bornite–covellite–pyrite–jalpaite with quartz–chlorite–epidote–amphibole; and
(3) low sulphidation Au veining event – this final event is defined by electrum (Au>Ag) associated with sinuous crustiform quartz veinlets and calcite-filled fractures, strong pervasive silicification, sericitization and disseminated pyrite mineralization.
Please click here to view the AME ROUNDUP 2023 Poster and paper published at International Geology Reviews.