The Chunibas property is located in the Sierra Madre Occidental area of Northern Mexico. The property area is more specifically located in the Sahuaripa District, which geologically consists of Cretaceous to Tertiary sedimentary and volcanic sequences. Marine sedimentary limestones, sandstones and siltstones belonging to the Lower Cretaceous El Palmar Formation are stratigraphically followed by Upper Cretaceous agglomerates, sandstones, and andesite tuffs. These El Palmar Formation sediments have been structurally sheared and thrust-faulted over the more recent sediments and andesite tuffs.
Overlaying the marine sediments and tuffs are a series of volcano-sedimentary rocks and andesitic flows. Regionally, this stratigraphy is known as the “Lower Volcanic Sequence”. Upper Cretaceous to Lower Tertiary granodiorite and andesite porphyries intrude these earlier marine sediment and volcano-sedimentary sequences. A Tertiary sequence of andesite-basalt flows and rhyolite tuffs known as the “Upper Volcanic Sequence” (likely post-mineral) overlays this stratigraphy.
Regionally, these units, particularly the interface between the Lower and Upper Volcanic Sequences, host several significant gold and silver deposits including the Mulatos, Dolores and La India mines amongst others.
Chunibas SW Discovery Highlights
San Marco has discovered high-grade Copper/Silver mineralization in an area on the Chunibas Project that has seen little exploration in the past.
- Copper oxides have now been recognized and sampled from random outcrop exposures scattered over at least 1.7 kilometre of strike, and at least 150 metres of width.
- Surface work to-date included 38 rock chip samples, of which 26% assayed greater than 1% copper and 50% greater than 0.2% copper. Samples included up to 5.9% and 6.41% copper and 65.6 g/t and 27.3 g/t silver (NR January 10th, 2018 and NR January 16th, 2018).
- An initial petrographic study has identified bornite, chalcocite, covellite and idaite as the primary copper minerals which appear associated with hydrothermal alteration. Microscopic textural features indicate that chalcocite, covellite and idaite are replacing bornite. The nature of the replacement could be a late hydrothermal event or supergene. The dominant alteration assemblage is represented by Iron – epidote -> chlorite > quartz > calcite.
- Host rocks are presumed to be Laramide age intermediate volcanics, which have variable textures, andesite breccias; porphyritic andesite and vesicular -amygdaloidal andesites.
- Copper and silver mineralization is mainly hosted in the andesite breccia which are moderately to strongly altered by an assemblage of epidote>chlorite>quartz>calcite>specularite. Mineralization occurs mainly as disseminations, patches, cavity fillings, minor veinlets and hydrothermal breccias.
- Ongoing exploration continues to expand the surface footprint. Geophysics, trenching and drilling are expected to be included in the 2018 exploration program.
Santa Fe Drill Results
|Drill Hole ||From [m]||To [m]||Interval [m]||Gold[g/t]|
|And||109.00||110.20||1.20||2.42 (last sample at the end of the hole)|
|And||118.00||120.20||2.20||6.74 (last sample at the end of the hole)|
|CHD-04||0.00||201.00||All breccia||High Arsenic/ Antimony. Low gold values.|
|CHD-05||6.00||8.00||2.00||0.28 drilled into andesite roof pendant |
All holes are drilled at – 60 inclination. CHD-01 azimuth (“az”) 90 degrees; CHD-02 az 305 degrees; CHD-03 az 90 degrees; CHD-04 az 90 degrees; CHD-05 az. 90 degrees; and CHD-06 az 315 degrees. True widths are presently unknown, as the discovery holes do not have enough information yet to identify where the holes are located in the mineralized system.