Martha Mineralized Zones
Silver and gold mineralization at Martha is located within a series of quartz-rich, locally banded and brecciated, veins and veinlets.    The style of mineralization has been interpreted to be intermediate-sulfidation in character (Paéz et al, 2015 and Sillitoe, 2005).  The main trend of the mineralized systems is WNW and EW and dip steeply to moderately to the S, SW.  On surface, mineralized structures can be several meters wide but often are much less than a meter in true width but may expand in width in the subsurface.

Base and precious metal-bearing minerals at Martha (Paéz et al, 2015 are galena, sphalerite, chalcopyrite, polybasite [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4], silver-bearing tetrahedrite, pyrargyrite (Ag3SbS3), freieslebenite (AgPbSbS3), acanthite and native silver.    Pyrite and arsenopyrite are common. Gold-bearing minerals have not been identified.

Dating of base and precious mineralization is often performed by dating spatially-related minerals.   At Martha, Sernageomin (2011), for Paéz’s thesis (Paéz, 2011), dated vein- hosted adularia (a low-temperature variety of orthoclase with the chemical formula KAlSi3O8) at 156.5 mya (million years ago).   The host rock was dated at 157.6 mya. Alteration assemblages at Martha have been studied by several workers including the exploration staff at Coeur (Birak et al, 2007) and can be generally grouped into major sets: propylitic, silico-argillic, argillic and silicic.    Cedillo Frey (2009) documented the following alteration observations at the Martha Oeste vein, which is situated on strike with, and west of, the Martha vein (translated and paraphrased from original Spanish by the Qualified Person).

“Crystallization of sericite, quartz and adularia occurred from pH neutral, hydrothermal fluids ranging in temperature from 200o to 250 o C.   This alteration developed two main zones.
a) An outer zone, extending 1 to 5 meters from the vein with sericite as replacement of potassium feldspar, plagioclase, biotite and phengite (muscovite-like mineral).  This alteration increased towards the vein forming muscovite and illite.
b) An Inner zone, extending less than 1 meter from the vein, with massive silicification.
In both zones, adularia can be found but is most abundant in the inner zone.”

Deposit Types
Silver and gold mineralization at Martha, along with lesser amounts of base metals, occurs within quartz rich veins, veinlets, breccias and stockworks.    The style of mineralization is interpreted to epithermal in original.    Epithermal silver and gold deposits, according to Sillitoe and Hedenquist (2003), occur as “both vein and bulk- tonnage styles may be broadly grouped into high-sulfidation (HS), intermediate-sulfidation (IS), and low-sulfidation (LS) types based on the sulfidation states of their hypogene sulfide assemblages”.   

According to Sillitoe (2005) “The overall characteristics of the Martha veins, in particular the occurrence of bonanza grades in association with massive sulfide bands, the high Ag/Au ratios, and the elevated fluid inclusion salinity values, suggest that the deposit is of intermediate-sulfidation epithermal type, albeit with some low-sulfidation features”.

The precious metal, vein-hosted deposits at Martha tend to occur in two general orientations: WNW and EW striking.  The location of the main Martha area veins have been inferred to be located along the S-SW margin of a Jurassic-aged volcanic caldera Martha veins can vary significantly in width, ranging from a few millimeters or centimeters (e.g., the Betty System veins) up to a few meters (e.g., Martha vein). However, what sets the Martha veins apart from other veins systems in the Deseado Massif are their bonanza metal grades which can exceed several thousands of grams of silver per tonne (Paéz et al, 2015) and very high silver to gold ratios.

High-grade silver and gold mineralization can be found in surface exposures but often may only be anomalous on surface; changing in tenor, width and orientation at depth.   The longitudinal section of contoured silver grades within the Catalina vein system (part of the Del Medio System) is a good example of how grades and the size of the mineralized zones can change with depth at Martha.

Martha historically was predominantly an underground operation with focus on two mining locations, each with its own access portal; the Martha portal (elev. 302m) targets the Martha vein and the R4 portal (elev. 310m) gives access to the R4, Catalina, Francisca and Belen veins.

The Martha side was the original entry to the mine while the R4 portal was developed after continued exploration verified the extension of the vein system to the east.  Both portals are open and utilized by Hunt today.

The lowest level of the Martha side is at 210 meters and the lowest elevation of the R4 is 145 meters. The two sides were later connected on the 210 meter.   Underground mining methods consist of drifting and shrinkage (methods successfully employed at Martha in the past) and caving of crown pillar blocks and extraction of rib, footwall or hanging wall remnants.    This work is accomplished without new development.  

Currently there are no underground haulage trucks and, after material has been mucked from the production face into the muck bay, transfers the rock to the surface using the mill loader.

Currently, a new 40 meter access drift is being developed using a portable jack-leg. It is targeting the underground portion of the Martha West occurrence that has so far been mined from the surface. This access is closer to the portal than the existing draw points in the Martha vein. As of April 2018 a raise is being developed from which horizontal drifting on the vein is planned to generate mill feed.

Aside from vein remnants from the Martha side, other remnants are accessible through the R4 portal.  Some of the R4 remnants lie below the water table.   Continued pumping will expose the remainder as needed

The mill consists of an industry-standard crushing, grinding and flotation circuit combination – nominally rated at 240 tonnes per day (tpd) though the equipment is capable to process up to 400 tpd.

The mill is running on a two-weeks-on and two-weeks-off basis. This allows enough mill feed to be generated to yield a 240 tonnes per day (tpd) throughput when operating, though the plant capacity is rated at 480 tpd.

The processing plant at the Martha Project has an estimated useful life of 8 years as it is anticipated that this plant will be used to process mineral from Cap-Oeste underground, Martha Project and from La Josefina Project.