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Commodity: Polymetallic – Au, Ag, Pb, Zn, Cu
Deposit Type: Manto-Chimney, Polymetallic system
Location: Sonora, Mexico
Size: 2,604 hectares
Status: Available for option

La Union Project is located in westerns Sonora approximately 30 km south of Caborca part of the orogenic gold trend and is within close proximity of major mines such as: Noche Buena, La Herradura and Cerro Colorado. La Union has only seen small-scale production dating back to the 1950s by Peñoles and local families. The Project has since been left unexplored until 2012, when Paget and Millrock started exploration work. High-grade rock chip samples taken by Paget and Millrock triggered Riverside’s attention to the project and in 2019, Riverside purchased the project as part of a five Mexico project portfolio acquisition (see press release of June 26, 2019).

Riverside has since worked on expanding its current footprint at the La Union Project evaluating the existing system of mineralization and its potential. Recent press release from October 2021 highlighted the high-grade gold mineralization (up to 59.8 g/t), Ag (833 g/t), Pb (5.8%), Zn (4.2%) in samples helping the Company better characterize the size of the system.

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Figure 1: location of La Union project within the gold belt of Sonora

Riverside’s initial field work included selective rock sampling from abandoned mine workings and dumps with results returning up to 59.4 g/t Au and 833 g/t Ag (see Table 1). Further exploration work will begin shortly as the Company has completed its review.

La Union Polymetallic Project was previously defined as a manto-chimney style deposit that could potentially be linked to a porphyry-skarn system further at depth. The ongoing work has been demonstrating significantly high-grades in gold, silver, lead and zinc across mineralized areas. Near surface, the oxide gossan cap and carbonate replacement bodies are particularly extensive with strong similarities with the Leadville polymetallic system in Colorado, USA. At La Union the Paleozoic carbonate stratigraphic section is a composite of over 1,000 m thick regionally and the mineralization of chimneys and mantos is unexplored.


Table 1: Sample Results from La Union Polymetallic Project.

Sample ID Au (g/t) Ag (g/t) Pb (%) Zn (%) Cu (%) Type Description
RRI7891 59.4 833 5.76 4.16 0.3 rock chip massive sulfide - dolomitic breccia
RRI7895 40 3.3     0.13 mine dump massive sulfide and jasperoid
RRI7894 8.3 239     0.17 mine dump jesperoid
RRI7890 1.367 50 1.63 1.43   mine dump sulfide-oxide bearing breccia
RRI7893 0.473 12.4       rock chip brecciated contact - dolmite/quartzite
RRI7889 0.072 76.4       rock chip brecciated contact - dolmite/limestone


Note: Six of the higher-grade due diligence samples out of eight total are shown in Table 1.

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Figure 2: Photo of sample RRI7891 from La Famosa Mine and RRI7895 from Plomito Mine

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Figure 3: Map of Riverside’s La Union Polymetallic Project, Sonora, Mexico. Highlights of the most recent results from rock sampling from Riverside

Mineralization is primarily located within the Paleozoic sedimentary sequence, known in this area for reaching up to 1,000 m in thickness and host to multiple historical mines. Regionally the mountain range is characterized by alternating limestone, dolomite and quartzite; regionally contact mineralization has been observed to grow into a manto-chimney style deposits. These types of deposits tend to have higher metal grades, making this style of deposition attractive for exploration.

Local historical productions in the 1950’s mined high-grade material averaging 7-20 g/t Au, 300 g/t Ag, 10-20% Pb and 5% Zn, for which mineralized bodies were traced for at least 80 m depth within oxides (Yantis, 1957). Since then, only small exploration programs have occurred including more recent work by Paget Mineral Exploration Company and Millrock Resources with sampling programs yielding up to 22.5 g/t Au and multiple high-grade polymetallic samples over the project area. The presence of many high-grade areas in addition to the thickness of the host rock and extent of the system across multiple known historic mines suggests an extensive system exits in this district.

Riverside has a 4-year term option on the properties with staged cash payments and no retained NSR. The terms for each respective properties (La Famosa and Plomito) are presented below:

0 On Signing $ - $ -
1 12 months $ 10,000.00  $ 10,000.00
2 24 months $ 15,000.00  $ 15,000.00
3 36 months $ 25,000.00 $ 25,000.00
4 48 months $ 50,000.00 $ 40,000.00
5 60 months $ 75,000.00 $ 75,000.00
TOTAL   $ 175,000.00 $ 165,000.00

The scientific and technical data contained in this news release pertaining to the La Union Project was reviewed and approved by Freeman Smith, P.Geo, a non-independent qualified person to Riverside Resources, who is responsible for ensuring that the geologic information provided in this news release is accurate and who acts as a “qualified person” under National Instrument 43-101 Standards of Disclosure for Mineral Projects.

Rock samples from the exploration program discussed above at La Union were taken to the Bureau Veritas Laboratories in Hermosillo, Mexico for fire assaying for gold. The rejects remained with Bureau Veritas in Mexico while the pulps were transported to Bureau Veritas laboratory in Vancouver, BC, Canada for 45 element ICP/ES-MS analysis. A QA/QC program was implemented as part of the sampling procedures for the exploration program. Standard samples were randomly inserted into the sample stream prior to being sent to the laboratory.

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Figure 5: Photos of the mineralization as seen in the field. La Union as shown comprises a quartzite bed bounded by oxide horizons. La Famosa (right) photo shows the working from the 1980s.