Underground exploration work on the southern end of the Rio Suro oxide gold zone at the Virgen property in north-central Peru is helping Gitennes Exploration (GIT-T) get a better handle on an area of high-grade breccia.
This zone of breccia was intersected in hole V97-10, which returned a 41.1-metre section averaging 14.88 grams within a 192.5-metre interval averaging 3.3 grams, starting at a depth of 6.1 metres.
A crosscut, which was driven in an east-west direction across a northerly-striking portion of higher-grade polymictic breccia, averaged 10.56 grams gold per tonne over 44.8 metres of core representing a true width of 41 metres.
The crosscut lies about 25 to 35 metres below surface and 8 to 35 metres above hole V97-10. Gitennes President Jerry Blackwell notes that there is no indication of the breccia zone at surface.
Results from the crosscut represent a weighted average of samples collected from the face and walls; higher-grade muck samples were not included. The results may be revised if Gitennes can reconcile the grade variation. For illustration purposes, a higher-grade 31-metre portion of the crosscut averaged 16.09 grams for the mucks and 12.79 grams for the walls and face.
The crosscut was completed at the northern end of the 66-metre-long North drift, which was driven along strike from the eastern edge of the breccia body. The North drift began from a point 25 metres inside a 138-metre-long access tunnel. It intersected 19.5 metres of fractured and brecciated quartz arenite averaging 0.47 gram, before encountering the eastern edge of the breccia zone, which averaged 4.53 grams over a strike length of 46.7 metres.
Blackwell says the higher-grade breccia was encountered earlier than expected and the drift stayed in the zone longer than anticipated. Evidence in the North drift suggests the breccia zone has been down-faulted to the south.
“This is a zone where we see clear evidence of an earlier phase of mineralization, which was probably identical to what were drilling on the [Rio Suro] Norte,” says Blackwell. “It is a zone of breccia and fracturing in the quartzite, that probably had an earlier alunite-enargite-quartz-pyrite mineralization which has subsequently been leached by hypogene oxidation.” Blackwell believes the copper has been stripped out of the system and has been silicified, with an accompanying increase in the grade of gold, and that there is a good chance that similar zones of hypogene alteration will be found in the Rio Suro Norte zone.
The high-grade breccia is a linear zone that has been previously intersected by surface drilling over a minimum length of 120 metres, across true widths of 9 to 40 metres and to a vertical depth of 65 metres. The zone is offset by faults at several locations, but remains open along strike and to depth.
Preliminary bottle-roll metallurgical testwork indicates gold recovery rates of about 95% on a quarter-inch grind. Gitennes has begun testwork on a much larger sample collected from underground.
The Rio Suro zone comprises a northeasterly-trending auriferous oxide zone of fractured and brecciated quartzite that is bisected by the Suro River.
Rio Suro Norte is a zone of sulphide-hosted, copper-gold mineralization to the north of the Suro River. Gitennes initially drilled a zone of oxide mineralization on the southern end of this zone and discovered the sulphide mineralization at depth. The zone has since been drilled fairly closely over a 290-metre strike length. Recent results include 53 metres averaging 0.56 gram gold and 0.15% copper, starting at a depth of 154.37 metres in hole V97-44, which undercut previously reported holes 18 and 21.
Hole V97-46 is a 50-metre stepout north of hole 44 and an 80-metre undercut below hole 21, which had intersected low-grade mineralization. Hole 46 returned 73.6 metres averaging 1.36 grams gold and 0.15% copper (including 6.75 metres averaging 11.45 grams gold and 0.81% copper), starting at a downhole depth of 109.4 metres.
Stepping out a further 50 metres to the north, hole V98-47 intersected 32.97 metres averaging 1.26 grams gold, beginning at a depth of 32.97 metres and including a 20.6-metre section grading 1.83 grams gold, 10.91 grams silver and 0.43% copper.
Hole V98-49 encountered 8.33 metres averaging 1.77 grams gold, 15.15 grams silver and 0.28% copper between a depth of 125.9 and 134.2 metres.
Becoming comfortable with the way the zone was lining up, Gitennes stepped out 150 metres north of holes 47 and 49 with hole V98-51, which hit 62.2 metres averaging 1.13 grams gold, 16.84 grams silver and 0.93% copper, starting at a downhole depth of 333.4 metres.
Assay results are not available for hole V98-52, which was drilled up-dip of hole 51, nor are they available for hole V98-54, which intersected the zone 100 metres farther north. A further 170-metre stepout hole is in progress.
Blackwell says that hole, V98-59, is critical, because trenching, soil geochemistry and geophysics clearly show an “interesting” trend in its vicinity. A zone of vuggy silica and alunite alteration appears to cap this area; hole 59 is testing beneath this cap.
Further stepout holes are planned. The company’s strategy is to define the length of the zone before embarking on infill drilling to establish grade distribution.
“Just like playing bridge, were going for length before strength,” says Blackwell.
At the end of the day, Blackwell expects the Rio Suro Norte zone will tie-in with the original Rio Suro [oxide] discovery. “Essentially, we’re looking at one large, mega-breccia body, a long linear feature hung up on a fault and showing tremendous strike length. In places, it blossoms and widens up to 200 metres and in other places it pinches down to 30 metres.”
The zone, including the original Rio Suro and the Norte zone, appears to have a strike length of about 1,750 metres.
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