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Exploration

2020 Exploration

The exploration program in 2020 will consist of 2,700 metres of drilling and downhole IP surveys which will be completed in several phases. The main objective of the proposed program is to significantly increase and upgrade tonnage at the copper-rich South Zone. This is designed to build upon the existing 2.47Mt of Measured and Indicated resource and 6.09Mt of Inferred resource delineated in the South Zone as highlighted in the Company's December 2019 PEA Technical Report.

The South Zone remains open in all directions according to geological data collected during the Company's previous exploration activities. The most southern drill hole in the South Zone (LS_ST_11) was one of the best holes encountered, with assays reporting 67.6m true width at 1.57% copper equivalent ("CuEq") grade. Indications are that the mineralization is open and expanding southward where the Company's first drill targets in this program are situated. Figure 1 highlights the initial and follow-up planned drill holes.

Figure 1

 

The Use of Geophysical Tools at Lagoa Salgada

Step 1: Gravimetrics

The first hints of an ore deposit at Lagoa Salgada came from gravity measurements made more than a decade ago. Ore minerals like galena, sphalerite and chalcopyrite are much denser than most other rocks because they contain large amounts of lead, zinc or copper and these are heavy elements. When systematic measurements of gravity are made over a property, concentrations of heavy minerals cause small but measurable increases in the local gravity field. 

Although the deep, volcanic rocks at Lagoa Salgada are covered by over 100 m of sedimentary cover the original drilling confirmed that a local increase in gravity was caused by the massive sulphide mineralization that they contain. Many drill holes later, Ascendant has measured this mineral resource at and used geophysics to explore in the undrilled area around the deposit. Where a local gravity high is accompanied by indications of conductivity and chargeability in the subsurface, there is a compelling case for drilling a borehole to establish the source of the anomalies. Extensions of geophysical anomalies away from the known deposit probably indicate additional mineralization to be added to the resource once it is confirmed by drilling.

Step 2: Induced Polarization (“IP”) and Resistivity Measurements from Surface and Down the Boreholes

In 2018, the Company reprocessed older data which was believed to have been analyzed incorrectly. This provided valuable information that allowed us to pivot plans for drill hole locations and was highly beneficial when it came to preparing the plans for the 2019 drill program.

Most rocks are insulators but many metallic minerals conduct electricity. A massive sulphide deposit like Lagoa Salgada contains many different ore minerals. It has enough conductive mineralization to stand out in measurements of how well electrical current flows through the ground.

Ascendant’s geophysicists used an IP/Resistivity combination survey that maps out both the conductivity of the ground and whether metallic grains deep underground can be charged like tiny batteries (or like an electrical Capacitor). This survey was designed to search for metallic minerals over a large area of the Lagoa Salgada Property (several kilometers across) to a depth of almost 400 m. The results enable Ascendant to make a three-dimensional map of the earth’s properties and see through the younger materials that cover the deposit.

During the survey, current from an electrical generator is passed through the ground and the voltage and current patterns are measured with a very sensitive voltmeter. This instrument also detects residual voltages that appear when minerals are charged by the current passing through them-- the property called Chargeability. 

When chargeability and conductivity occur together it is a strong indication of metallic mineralization.

More On Resistivity

Resistivity and conductivity are just two different ways of looking at the same property of a material.

When a voltage is applied between a couple of distant electrodes plugged into the earth, a current will flow between them. The amount of current that will flow is proportional to the electrical conductivity of the ground between the electrodes.  Conductivity is a characteristic property of the material. It is usually high for metallic ore minerals but low for insulators like barren rocks.  Conductivity measures how well a material carries electrical current.

Resistivity is just the opposite - "Unconductivity" in a fashion. It is the ability of the earth materials to hinder the flow of current.

In geophysics, such surveys are usually referred to as "Resistivity" surveys because most earth materials are quite resistive.  Only a few minerals are highly conductive and often these are important ore minerals. "Conductors" are unusual and special because they may indicate the presence of metallic mineralization. The blue colours on the Ascendant resistivity maps and models indicate low resistivity or (equivalently) high conductivity, compared to typical rocks.

In exploration for massive sulphide mineralization these "conductors" show the most prospective places to test with drilling.    

How Do We Use These Tools to Propose Drill Hole Locations?

These tools show us where we have concentrations of metallic grains in the rock.  Generally, massive sulphide mineralization is shown by conductors with high chargeability. The chargeability also shows that we have metallic minerals but because they are imbedded in a non-conductive rock we can charge the grains like batteries. When we map a blue resistivity low and a pink chargeability high in the same place, it is a good drill target. We display both kinds of data in three dimensions to pick exact directions in which to drill, giving the best chance of hitting mineralization. Geophysics does not provide indications of grades or metal types – we need to drill for those results.

Our Recent Work

Again, targeting with geophysics has been very useful so far in finding mineralization. We can see that the anomaly extends well beyond the resource that we know at Lagoa Salgada. When we get a conductivity, chargeability, and gravity high all together there is a very good chance that this is because there is more mineralization there and only drilling can test that.  

Lagoa Salgada West: The North Zone

The Model Resistivity at depth measured using Drill Holes in the North Resource shows the massive sulphide as a clearly outlined conductivity anomaly (blue) that extends deeper and to the northwest, beyond the 2019 drilling (Figure 1). It also extends 150m to the south and 100m deeper than the North Zone Massive Sulphide mineralization known from the 2019 drilling. 

Figure 1

The size of the Lagoa Salgada North Resource will likely increase as drilling extends in both directions. The extent of the conductor is limited by a lack of IP/Resistivity data farther south, not mineralization. The North Resource remains open to the South-Southeast.

A cross section of the Chargeability Model through the North Resource shows that, like the conductivity, this anomaly (pink) extends to the North, beyond the limits of the 2019 drilling (Figure 2). It also shows a peak in Chargeability that extends more than 150 m south and 100 m deeper than the massive sulphide mineralization defined in the Spring 2019 North Resource. The two tools show overlapping and coincident conductivity and chargeability peaks, where gravity is also high.

Figure 2