Plomosas – Geology
The high grade Plomosas base metal mineralisation appears to comprise predominantly intrusive-related hydrothermal replacement of limestone rich sedimentary units within a well-defined stratigraphic horizon, similar in style to Mississippi Valley Type (MVT) deposits.
Mineralisation in the Plomosas district exists as stratiform sheets of manto style mineralisation with cross cutting “chimneys” influenced by the location of crosscutting linking faults. The host rocks are predominantly limestone and shale with marbles present in areas including the hanging wall sequence. The hanging wall to the mineralisation is constrained by a zone of ductile-brittle deformation that is part of a larger ‘horst’ structure where a series of normal faults cross cut a sequence of folds and thrusts. This system of brittle deformation is evident along a series of normal sub vertical faults generally striking NW-SE.
At Plomosas, the average thickness of the manto style mineralisation is over 3m within a thicker sequence up to 25m thick containing limestone + shale ± marble that dips uniformly at low angles (10° – 40°) to the north east. Mining has extensively focused on the limestone units and shown the ore to be highly visible with sharp contacts.
Plomosas – Technical and Legal Investigations
Due diligence completed in early 2015 by SRK Global and ARC Resources Pty Ltd on behalf of the Company returned positive results which are summarised below:
• the style of mineralisation and tenor of grades have been confirmed along with the prospectivity for identifying significant additional high grade mineralisation;
• targets for immediate drilling and resource definition programs have been identified which are immediately accessible;
• there is moderate capital requirement to refurbish the mine infrastructure which includes production and ventilation shafts and many kilometres of underground mine development.
• underground mine ground conditions and geotechnical requirements have been identified as good and manageable;
• the existing processing plant can be refurbished to treat ore up to a rate of 200 tonnes per day for potential early production but will need to be largely replaced if or when production is increased to 500 – 1,000tpd; been of high quality and in high demand for blending with ore from other operations in the region;
• Capital and operating costs are anticipated to be low on a global comparison and in line with other operations in the immediate region however further work will be required through scoping and feasibility studies to confirm and quantify these estimates.
The legal and commercial due diligence similarly provided a level of comfort as to the status and good standing of the Plomosas tenements and ownership and the framework of operating in Mexico.
Plomosas – Recent Sampling Results
Analytical results of a number of channel and grab samples recently taken from various parts of the Plomosas underground workings to better understand the grade distribution of the mineralisation are tabled below in Table 1.
Note that some channel and rock samples returned such high grades of zinc that the values exceeded the upper detection limit of the ore grade analysis method used by ALS Laboratories. These samples are currently being re-assayed using the method of analysis for concentrate material.
Two samples, LVL5ST and TRS1, have highlighted a previously unexplored area that justifies additional investigation. Both these samples represent areas located in the footwall to the main manto mineralisation and both samples represent a different style of mineralisation to that observed in the manto itself.
• Sample TRS1 assaying returned grades of 24.2% Zn, 0.80% Pb, 13.3g/t Ag and represents mineralisation derived from a massive sulphide replacement style zone called Tres Amigos.
• Sample LVL5ST returned assays of 16% Zn, 12.2% Pb, 28g/t Ag and is interpreted to come from a chimney system (or feeder zone) possibly linking the historically mined marble unit and the Tres Amigos horizon.
Figure 2 shows the areas from which the various samples were taken, with Figures 3 to 7 showing the sampled areas in more detail. Figure 2 is a section showing the current work in progress along with a generalised interpretation of the mineralised zones within the deposit. All figures are located in Appendix
High zinc grades continue to validate the Company’s view that the Plomosas deposit is amongst the highest grade zinc projects currently being explored or mined and the imminent commencement of our first drilling program is an exciting time for the Company.