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.
Chunibas hosts a stratiform, volcanic hosted copper/silver zone. The stratiform, volcanic hosted style of mineralization seen at Chunibas shares remarkable similarities to productive copper-silver deposits in Chile but has no comparison in Mexico. An independent geological expert in this style of mineralization recently confirmed to San Marco that the mineralization is identical to that of the copper-silver systems in northern Chile. This suggests that the processes responsible for development of the Chilean ore deposits (such as the ones from Mantos Blancos district) may have also occurred at Chunibas.
Observed similarities between the Chunibas copper/silver mineralization and known and comparable Chilean systems include:
- Mineralized top and bottoms of intermediate volcanic rock units. Mineralized volcanics at Chunibas display brecciation and vesicles similar to Chilean deposits.
- High grade and stratiform-like mineralization with variable dimensions along strike and down-dip.
- Non-supergene specularite-bornite-chalcocite-(digenite) and covellite assemblage and paragenesis.
- Early stage alteration assemblage is comprised by epidote-chlorite-quartz-specularite.
Mineralized outcrops are difficult to sample due to their craggy and erratic nature. Where continuous chip channel sampling over stratiform units could be completed, examples assays results from the discovery zone are;
- 10.5 metres of 1.13% copper and 16.91 g/t silver
- 7 metres of 2.19% copper and 27.3 g/t silver.
Exploration work in preparation for drilling included;
- Detailed geological mapping over the entire 1.7 km of known strike length. Mineralized volcanic units tend to have slightly varied composition and fabrics compared to less mineralized units, therefore, detailed mapping of individual units is important. In addition, mapping efforts are focused on the identification and distribution of different copper sulphides since these (similar types of Chilean systems) show specific zoning of different forms of copper mineralization.
- Hand trenching outward from known mineralized outcrops with the intention of defining the continuity between and within the multiple mineralized units and between current surface exposures.
- An XRF (X-ray fluorescence) rock (outcrop) analysis program for copper/silver over every outcrop within the known extensions of the mineralized corridor. Handheld XRF units provide immediate geochemical analysis (similar but more qualitative than a laboratory assay) of rock exposures. This technique is widely used by exploration companies for fast analysis of metals and pathfinder elements.
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.
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 degree 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.