map 04S

Commodity: Gold and Silver
Deposit Type: Low Sulphidation Epithermal Au-Ag Rhyolite Flow Dome Complex
Location: Sonora, Mexico
Size: 68.9 km²
Status: Drill Permitted, Available for Option

The drill permitted Cecilia project is located 40 km southwest of the Mexico-U.S.A. border town of Agua Prieta in Sonora, Mexico and is easily accessed by paved highway and dirt roads. The project is 6,897 ha in size and is located 48 km from the world-class open-pit Cananea porphyry copper mine. Deposit analogs for Cecilia include the La Pitarrilla deposit containing 526 million oz Ag (Measured + Indicated, SSRI website) and Fresnillo’s San Julian silver mine containing over 230 million oz Ag, both located in Durango, Mexico.

As many as 30 abandoned exploration adits, small underground galleries and surface prospect pits are distributed over the upper slopes of Cerro Magallanes, which are believed to date back to the early decades of the 20th Century. 

In the early 1980s the Consejo de Recursos Minerales (CRM) initiated a project at Cerro Magallanes. Over a 3-year period CRM carried out a comprehensive exploration program, including

  • 896 km2 squared of regional mapping
  • 635 surface rock chip samples
  • 14.3-line kilometres of induced polarization
  • 1,412 m of underground mapping
  • drilling of 4 diamond drill holes totalling 732.3 m

In April of 1994, Cambior Exploracíon S.A. de C.V. entered into an option-to-purchase agreement with the DGM for the project. Under the agreement Cambior was obligated to incur exploration expenditures totaling $700,000 in the first 18 months, $1,900,000 in the second 18-month period and $5,400,000 during the following 36 months. Cambior terminated the contract at the end of the first 18-month term, their work is summarized below:

  • 9 km2 1:2,500 orthophoto and topo map with 5 m contours
  • 6 km2 of geological mapping at 1:2,500
  • 12.85 line kilometres of induced polarization, ground magnetic survey over 2.8 km x 2.4 km
  • 666 surface rock chip samples
  • 1,200 m of underground mapping, 388 underground rock chip samples
  • drilling of 19 diamond drill holes totalling 3,817.6 m

Minerales El Prado S.A. de C.V. (“El Prado”), the Mexican subsidiary of Chesapeake Gold Corp., was the next company to acquire the project. El Prado conducted rock sampling programs between 2004 and 2009 and collected a total of 738 surface rock chip samples. From 2009 until 2013 essentially no work was done.

In February of 2013, Precipitate Gold Corp. entered into an option agreement with Gunpoint Exploration Ltd., who then controlled the La Cecilia project. To acquire 100% of the project, Precipitate was obligated to pay Gunpoint in three installments a total of $400,000 cash and issue a total of 525,000 common shares over a 2-year period. Minera Pendiente conducted due diligence work on behalf of Precipitate Gold, collected 43 surface rock chip samples and resampled and analysed 35 samples from 2 drill holes. Precipitate decided not to finalize the agreement with Gunpoint Exploration. 

During 2017, Riverside completed a work program of rock-chip sampling that was designed to primarily confirm the existence of the more intensely mineralized gold occurrences found on the Cerro Magallanes flow dome. The sampling work was done within an area of roughly 1 kilometer by 200 meters at the core of the project area and mainly on the eastern and northeastern slopes of Cerro Magallanes. Riverside’s program confirmed the work done by previous operators. More recent work has focused on mapping and target generation on the flow dome but also elsewhere on the property. Riverside recently completed a large soil grid over the dome and surrounding area which shows not only the known areas of gold mineralization but also new areas both on and below the flow dome.

Riverside completed a 1st phase exploration program at the North Breccia and Central Zones in 2017 collecting 91 rock chip and grab samples. Thirty-three (33) of the 91 samples yielded gold assays greater than 0.5 g/t gold (Au) with five samples assaying greater than 3 g/t Au. The maximum assays were 113.7 g/t Au & 288 g/t Ag within old working on the volcanic dome. Riverside’s exploration team is targeting epithermal gold-silver mineralization hosted by a felsic volcanic flow-dome complex.

The three-best sampled assays were (see press release dated June 6, 2017):

  • 113.7 g/t Au with 288 g/t silver (Ag)
  • 58 g/t Au with 207 g/t Ag
  • 8.42 g/t Au with 87.8 g/t Ag

Nineteen (19) of the 91 samples have silver contents greater than 100 g/t Ag, six of these samples yielding assays that were greater than 200 g/t Ag and the maximum silver assay was 310 g/t Ag.

In September of 2018, Riverside completed a regional soil sampling program. The soil survey covered approximately 30% of the recently acquired 50 km2 Cecilia 1 concession (see Diagram below and press release dated March 5, 2018), and has expanded the targeting around the previously known central Cerro Magallanes area of the Cecilia Project. The Company continues to advance and refine the known central targets and is also placing equal priority on new property-wide target generation.

In October 2018, Riverside reported on rock chip channel samples from the Cerro Magallanes area continuing to expand exploration to different regional areas at the Project (see press release dated October 2, 2018). Riverside’s rock sampling results from the main central rhyolitic dome complex verifies and expands upon historical sampling for gold within breccias and veins on Cerro Magallanes. Dome margins also show positive potential for near surface gold targets and indications for potential gold and silver bodies at depth. The channel sampling program included 305 samples ranging from <0.05 to 19.00 g/t Au. Sampling shows consistent gold from the top of Cerro Magallanes at the San Jose Target northeast along the Agua Prieta-North Breccia Target and through the Central and East Target areas. (See Figures below).


riverside1 riverside2

 cross section of

Riverside outlines 4 (four) new target areas with soil sampling program

 Rene Section Targets Edit

Cross Section of the Cecilia Project


In March of 2018, Riverside was granted the mineral rights to the Cecilia 1 concession, which had been applied for in November of 2017. Obtaining the Cecilia 1 claim significantly increases the total area covered by Riverside’s Cecilia Gold Project. The expanded project area now covers approximately 6,000 hectares, about 6.7 times greater than the original area of the Project.

cecilla diagram 1l

Map of the Cecilia Project (Cecilia 1 Concession)


The Cecilia project is centered on a large middle Tertiary age (Oligocene) rhyolite flow-dome complex that forms the prominent topographic feature of Cerro Magallanes. The dome complex intrudes and unconformably overlies a sequence of marine clastic sedimentary rocks consisting of interbedded siltstone and fine-grained sandstone and thin layers of intraformational, immature pebble conglomerate (middle Cretaceous Cabullona Group). The upper portion of the flow-dome complex is composed of a mixture of massive, porphyritic quartz-feldspar flows flow-breccias and banded rhyolite.  The lower portion of the complex, as documented in drill-hole logs, is comprised of rhyolite lithic tuff, tuff-breccia and clastic sedimentary rock (fragments supported by a tuffaceous, rhyolitic groundmass).  Irregular bodies of talus breccia exist as a litho-facies within the pyroclastic units.

Gold mineralization is concentrated within an area of 1,000 meters extent in the east-west direction by 200 meters north-south, with the peak of Cerro Magallanes being at the western end of this zone. Multi-element geochemical data shows that gold is inconsistently associated with anomalous concentrations of Ag, Mo and Pb.  The correlation coefficient for the element pair Mo:Pb is 0.942, whereas the correlation coefficients for Au:Ag, Au:Mo and Au:Pb are only 0.274, 0.248 and 0.089, respectively.  Significant concentrations of silver occur at lower elevations in the flow-dome complex at the eastern limits of the 1,000 m by 200 m zone of mineralization that has been defined at Cecilia.  

West Target Area

The main Cerro Magallanes peak with its abundant workings occur along a northwesterly trending ridge.  Riverside collected 45 rock-chip samples on the ridge where  gold is seen to be very finely disseminated in quartz-iron oxide (hematite-goethite) stringers and veinlets as well as in small dikes and irregularly shaped zones of brecciation in the flow-dome rocks along the ridge. The highest gold assay obtained was 2.69 g/t Au.  These auriferous samples show slight enrichments in Mo, As and Sb. 

An underground working consisting of a 90m-long adit and three levels of small galleries for a total working length of 184 meters exists in the central part of the target area.  Identified as Obra 26, the working’s ‘galleries’ are aligned NW-SE, apparently following a regional mineralized structure with this orientation. Cambior’s sampling of Obra 26 produced 32 chip-channel samples with gold ranging from 0.2 to 4.76 g/t Au, with 14 of these samples assaying greater than 1.3 g/t gold.  The working was developed in moderately to highly fractured rhyolite porphyry containing abundant disseminated and fracture-controlled hematite along with veinlets of quartz and fluorite.  Hematite appears to be partially derived from the oxidation of disseminated pyrite.  No drilling has been done in the West target area which is a high priority target for Riverside.

North Breccia Target Area

The North Breccia target area is located on the northeastern slope of Cerro Magallanes. This zone forms a prominent zone of iron oxide staining, which has demonstrated some of the most extensive gold mineralization found on the property.  The target area has an outline of about 250 m by 100 m and is marked by multiple zones of hematite stained hydrothermal brecciation, locally, with open-space crystallization of colourless quartz and purplish-colourless fluorite. Quartz ± fluorite veinlets and stringers are also common.  Alteration consists of widespread disseminated and fracture-controlled hematite and hematite clay-rich gouge found in a number of mainly NW-SE trending minor faults.  Of the 21 rock-chip samples collected by Riverside in this area, 18 samples returned gold assays ranging from 0.447 to 7.46 g/t Au.  Gold is the only trace element that is noticeably enriched in the mineralized rocks. 

The CRM tested this area in 1983 with drill hole DDH-83-03; the hole appears to have passed through strongly fractured and faulted flow-dome lithologies that display structurally controlled silica and chlorite alteration.  The geological drill log shows it passed through variably silicified and chloritized porphyitic rhyolite for approximately 135 m, then chloritized and intensely fractured banded rhyolite for 30 m, and at a down-hole depth of 195 m it entered into rhyolite lithic tuff. Core samples were apparently collected for the entire length of the borehole and returned positive numbers for gold however  the assaying method that was performed on these samples was quite rudimentary, and as a result are unreliable.

Cambior tested this area in 1995 with four drill holes (138-95-08, 138-95-15, 138-95-18, 138-95-19). The best drill-hole intersection of gold mineralization was obtained in hole 138-95-08 that averaged 1.41 g/t Au over 30.0 m, starting 4.0 meters down the hole. Gold assay values for individual core samples, each being 3.0 m in length, ranged from 0.32 to 3.33 g/t Au. No other gold pathfinder elements were enriched in this zone. Drill-hole 138-95-19 appears to have passed through a portion of the same mineralized zone intersected by hole 139-95-08 and produced an 8-meter-long interval, starting 48 m down-hole, that averaged 0.653 g/t Au.

Central Target Area

A linear series of pits and small underground workings extend from the peak of Cerro Magallanes eastwards down slope and define the Central target area. The westernmost occurrence of gold mineralization was sampled by Riverside at an elevation of about 2,170 m.a.s.l.  Two adjacent 1.5 m long chip-channel samples returned gold assays of 3.0 and 7.9 g/t Au, with another 2 m-long sample collected 5 m to the west assaying 9.0 g/t Au.  Samples were collected along a fault breccia containing crystalline quartz, which is suggested to be striking to east-northeast with a moderate dip to the south-east.  It is possible that the intersection of this structure with the 35-40° easterly inclined slope surface of Cerro Magallanes has resulted in the linear array of gold showings, tested by historical workings and several Cambior drill-holes. 

At an elevation of about 1,930 m.a.s.l. are the underground workings of Obra 16 consisting of an adit and small galleries on three levels, 5-10 meters apart, that together have a length of 438 m. Thirteen Cambior samples on the upper level of the working assayed between 0.5 and 7.4 g/t Au, with another 16 samples from the deepest level assaying from 0.5 to 2.6 g/t Au. Riverside chip-sampled up-slope from Obra 16 with 15 samples assayed between 0.5 and 3.38 g/t Au.  Further up-slope are the entrances to workings of Obra 19 and Obra 20.  Two boulders from this old working of coarse-grained, cockscomb-textured quartz veining returned high-grade Au-Ag mineralization; samples 2466 and 2473 assayed 58.0 and 133.7 g/t Au, and 288.0 and 87.8 g/t Ag, respectively. 

The eastern end of the target area is marked by a 20 m by 12 m collapsed open-cut or ‘glory-hole’ that connects to the underground working of Obra 13. Cambior’s sampling exposed quartz- and feldspar-porphyritic rhyolite hosting quartz-fluorite stringers, veinlets and patchy breccia matrices with 22 samples assayed between 0.5 and 4.2 g/t Au. Riverside collected 12 chip-channel samples that ranged from 0.2 to 3.31 g/t Au and 13.1 to 145.6 g/t silver. The greater concentrations of silver at this lower level is worth noting as it appears to be indicating the transition from gold-only mineralization found at higher elevations into a Au-Ag zone where Pb and Zn are also somewhat enriched (100’s of ppm’s).

The eastern half of the Central target area between Obra 16 and higher elevation workings of Obras 19 and 20 was tested by 5 drill-holes, 4 done by Cambior (138-09, -10, -13 and -17) and one drilled by CRM (DDH-83-4).  Assays from the five drill-holes were generally low,  Hole 139-95-17, drilled to the northwest at an angle of 45°, intersected a relatively broad zone of gold mineralization that started 30 m down-hole and continued to 72 m in the hole, averaging 0.49 g/t Au.  The maximum assay for this mineralized intercept was 3.26 g/t Au.

The eastern end of the target area, where the workings of Obra 13 and Obra 14 are found, was tested with another two Cambior drill-holes, 138-95-02 and 138-95-07, both of which returned no significant assays.

East Target Area

The East Target area is represented by a north-easterly trending ridge on the lower eastern slope of Cerro Magallanes and is defined by clusters of anomalous gold.  At the southern end of the target area is the small underground working of Obra 10, while at the northern end, about 180 m NNE of Obra 10, are the workings of Obra 6 which occur at about 1,720 m.a.s.l., the lowest elevation of all the historical workings found at the project. Maximum gold assays for underground samples collected by CRM and Cambior were reported as 3.84 and 1.964 g/t Au, respectively.

Fifteen Riverside chip-channel samples from this area returned between 0.19 and 2.35 g/t Au. Material collected at the entrance of Obra 6 assayed 8.421 g/t Au and 207 g/t Ag while another sample of quartz vein ‘float’ assayed 13.9 g/t Au indicating the high-grade potential at Cecelia

The East target area was poorly drill-tested by past explorers. Cambior’s hole 138-95-03 was drilled to the southeast directly beneath the working of Obra 10, while hole 138-95-06 was drilled from the other side of the ridge in a WNW direction, stopping short of the inferred mineralized structure that was sampled on surface and in the old workings. Neither of the drill-holes intersected any appreciable gold. CRM drill-hole DDH-83-01 was collared about 70 m west of the Obra 6 working and was inclined to the southeast Riverside believes these drill holes wer not properly located to intersect the intended mineralized zones.

In January of 2017, Riverside Resources Inc. purchased the Violeta concession from Millrock Resources Inc. for C$10,000, 100,000 Riverside shares and by granting Millrock a 0.5% Net Smelter Return royalty. Riverside concurrently signed an option to purchase agreement with Gunpoint Exploration Ltd. to acquire a 100% interest in the three Cecilia-Margarita concessions by making the following cash payments and share issuances:

  • the payment to the Optionor of a non-refundable deposit of $10,000 concurrent with the execution of the Letter Agreement; (paid)
  • the payment to the Optionor of $15,000 and the issuance to the Optionor of 100,000 common shares of Riverside concurrent with the execution of the Mexican Agreement* (the “Effective Date”); (paid)
  • the payment to the Optionor of $25,000 and the issuance to the Optionor of 200,000 common shares of Riverside on or before the first anniversary of the Effective Date; (paid)
  • the payment to the Optionor of $75,000 and the issuance to the Optionor of 300,000 common shares of Riverside on or before the second anniversary of the Effective Date;
  • the payment to the Optionor of $125,000 and the issuance to the Optionor of 400,000 common shares of Riverside on or before the third anniversary of the Effective Date.

The Cecilia-Margarita concessions are subject to a 1% NSR royalty in favour of the Servicio Geologico Mexicano (formerly Consejo de Recursos Minerales).

Riverside has compiled historical sampling and drill-hole data and has begun defining future drilling targets. Fieldwork in 2018 has confirmed the existence of large regional northwest trending faults that service as conduits for mineralizing fluids. The larger northwest trending faults are intersected by smaller northeast and east-west structures which serve as areas of deposition for the rising gold bearing fluids. These complimentary structures have been mapped by Riverside and outlined by recent soil sampling surveys. Riverside’s 3D model of the litho-structural setting and the controls on the Cecilia mineral system shows a relationship of rhyolite dome-related polymetallic ore systems providing high-potential drill targets at various levels in the gold-silver mineral system, including targets that are not readily apparent in bedrock exposures found at surface.

The scientific and technical data contained in this news release pertaining to the Cecilia 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.