An induced-polarization (IP) survey across the high-grade Navidad silver discovery in the Patagonia region of southern Argentina has identified a large chargeability anomaly with a surface footprint of 1.6 by 1.3 km that starts near the surface in areas of exposed mineralization and extends more than 1 km into the valley under an area completely obscured by soil cover.
IMA’s geological team has mapped large areas of consistent replacement-style galena matrix breccia over a cumulative strike length of several kilometres within a 5.8-km-long, elevated metal soil anomaly. Early sampling of this matrix style of replacement mineralization yielded an average grade of 158 grams silver per tonne and 8.9% lead from the first 41 randomly collected chip samples. Additional sampling, at Galena and Barite Hills, has been completed, and results are expected soon.
Situated in the north-central region of Chubut province, Navidada is wholly held by IMA. The project centres on newly discovered bonanza-grade feeder structures hosted by felsic-flow dome rocks that partially outcrop along the crest of Navidad Hill. These high-grade structures and peripheral calcite-barite veins occur in a core area measuring 475 metres long by 60-140 metres wide. The exposed structures, often obscured by a thin slope cover, range in thickness from less than 1 metre to 3.3 metres, and have been mapped over a cumulative strike length of 636 metres.
The average grade of 119 chip samples collected across the structures runs an impressive 5,546 grams silver (162 oz.) per tonne, 9.8% lead and 3.8% copper. Based on the results of soil sampling and a few isolated rock samples, IMA’s geologists believe the bonanza-grade mineralization and flow dome may extend farther to the southeast beneath a thin cover of post-mineralization volcanic tuff.
Recent mapping has identified several areas of significantly mineralized “carapace breccia,” a thin unit occurring along the margins of the felsic volcanics. In total, 50 chip samples, taken from three areas measuring 150 by 50 metres, 20 by 18 metres, and 25 by 20 metres, averaged 3,785 grams silver (110 oz.), 2.1% lead and 3.7% copper.
IMA recently completed a grid soil-sampling survey that outlined elevated levels of silver-lead-copper over the entire 5.8-km-long survey length, including spectacular values of up to 531 grams silver, 2.39% lead and 574 parts per million (ppm) copper from areas outside of Navidad Hill.
The soil survey saw a total of 958 samples collected at 50-metre spacing on lines set 100 metres apart, or 50 metres apart in key areas. A strong soil anomaly measuring 1,700 by 300 metres covers the Navidad Hill and Galena Hill areas. It is defined by greater than 2 grams silver and generally greater than 100 ppm copper. Within this zone is a central, 600-by-200-metre core of greater than 10 grams silver in soils (including values of up to 298 grams silver). Portions of this central zone correlate well to the outcropping bonanza-grade feeder structures. Two other significant soil anomalies were outlined at Barite and Calcite Hills.
Quantec Geoscience completed gradient IP geophysical surveys totalling 80 line km at 200-metre line spacings over a 6.2-by-2.5-km area of Navidad. A more precise, time-domain pole-dipole IP survey was performed in the area of the large gradient anomaly, providing additional, 3-dimensional information on the size and shape of the chargeability anomaly.
Keith Patterson, IMA’s exploration manager, says the anomaly is peripheral to the southwestern margins of the Navidad Hill zone, extending about 1 km into the valley. “It fits the mineralization model nicely,” says Patterson. “With the basin down-dropping on that side, that’s where we expect to find either massive sulphide mineralization or more of the galena matrix breccia replacement-style.”
Geologically, the Navidad discovery is hosted in an Upper Jurassic series of mixed calcareous sediments and intermediate volcanics mapped by government geologists as the Canadon Asfalto Formation. A series of felsic flow domes have intruded into a basin that is generally filled with carbonates. Carapace breccias are peripheral to, and overlie, the domes. “It’s essentially the broken-up margin of the dome,” explains Patterson. A surrounding “wedge” of heterolithic breccia was formed from material shedding off the flanks of the felsic domes.
“We have mapped normal faults, which are dropping down on the west side, so we expect more of the breccias to be shedding over that way,” says Patterson.
The high-grade structures in the felsic flow dome are interpreted as feeder structures to mineralization that comprised extensive areas of sulphide replacement of unconsolidated volcanic breccias.
With winter weather quickly bringing IMA’s field season to a close at Navidad, the company is conducting a follow-up gravity survey over the chargeability anomaly, having just completed a magnetic survey over the entire IP grid. Once all results have been received and interpreted, IMA’s technical team will begin preparing for an initial drill program of 4,000-6,000 metres.
IMA has 33.4 million shares outstanding, or 43.6 million fully diluted, and just under $4 million in cash. The company is trading around $1.40 in a 52-week range of $1.65-0.34.
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