The mining newspaper for Alaska and Canada's North
The mining newspaper for Alaska and Canada's North
Drills tap flat-lying veins associated with Gray Lead feeder North of 60 Mining News – March 11, 2022
This diagram illustrates the geological model developed for Pogo after high-angle veins feeding the flat-lying veins traditionally mined were discovered. Tectonic has made a similar discovery at the Gray Lead veins on its Tibbs property.
Tectonic Metals Inc. March 10 announced that its 2021 Phase II drill program at the Tibbs gold project in Alaska's Goodpaster Mining District has discovered the elusive low-angle, Pogo-style veins at Gray Lead West.
Located about 22 miles (35 kilometers) southeast of Northern Star Resources Ltd.'s Pogo gold mine, Tibbs is known for high-grade gold targets. While high-angle feeder veins similar to those found at Pogo had previously been identified at Tibbs, the stacks of more flat-lying veins that provide the bulk of the ore at the neighboring underground gold mine had yet to be found at Tibbs, or anywhere else outside of Northern Star's property.
One of the primary focuses of the second phase of Tectonic's 2021 program was to test for Pogo-style, low-angle veins in the previously unexplored gneissic rocks in the western half of the Tibbs project area with widely spaced reconnaissance holes in four distinct structural blocks.
This reconnaissance drilling tapped multiple layers of low-angle veins just west of Gray Lead, a steep vein that carries high-grade gold values.
"After multiple explorers and years of trying, the elusive low-angle quartz veins carrying Pogo-style gold mineralization have now been discovered at Tibbs," said Tectonic Metals President and CEO Tony Reda. "To appreciate the significance of this finding, one must understand the history, geology and exploration model of Pogo and how it relates to Tibbs."
This history goes back to 1988, when the group that originally discovered Pogo tapped 3.81 meters averaging 34 g/t gold in the high-angle veins at Gray Lead. Subsequent drilling at this high-grade target include holes that cut 5.7 meters of 19.14 g/t gold, 5.3 meters of 15.76 g/t gold, and 4.26 meters of 6.13 g/t.
At Pogo, high-angle veins were discovered after mining began. This discovery led to an updated 2013 geological model that shows these high-angle veins fed the high-grade gold mineralizaton into the low-angle veins that carry the largest tonnage of ore at the underground mine.
Unlike Pogo, where the partially eroded upper flat vein led to the discovery, the high-angle veins that came to surface were discovered first, followed by low-angle veins.
"Is Tibbs Pogo?" Reda asked. "Well, no; however, understanding Pogo is vital to understanding Tibbs; even more so now that all the elements of the Pogo Exploration Model are confirmed at Tibbs."
"Our drill discovery of multiple stacked intervals of high-grade, low-angle veining represents an excellent exploration opportunity to delineate the extent of the Tibbs' Gray Lead system and test for areas of increased grade and thickness," he added.
A total of 959 meters of drilling was completed in four holes at Gray Lead West last year.
Diamond hole TBDD21-012 cut four low-angle quartz veins, including one vein that returned 9.95 g/t over 0.75 meters from a depth of 223 meters and another vein encountered at 342.7 meters that returned 0.6 meters averaging 7.64 g/t gold.
The vein intervals exhibit the same morphology, mineralogy, and gold-arsenic-bismuth-tungsten-tellurium geochemistry as the high-angle Gray Lead vein just 300 meters to the east, which is interpreted as a feeder vein to the low-angle veins intersected in TBDD21-012.
Additionally, TBRC21-003, a reverse circulation hole completed 700 meters west of TBDD21-012, cut 3.04 meters of quartz vein-hosted mineralization averaging 2.21 g/t gold from a depth of 120.4 meters. This interval appears to be correlative along a low-angle structure with visible gold observed in TBRC21-001, another RC hole that cut 3.05 meters averaging 1.37 g/t gold, as well as a 1.52-meter interval of quartz veining cut by TBRC21-002 grading 0.39 g/t gold.
Tectonic says the vein mineralization drilled along a 700-meter strike at Gray Lead West is the best example of low-angle quartz vein-hosted gold found in the Goodpaster Mining District outside of the Pogo footprint and was intersected where predicted by the 2013 Pogo geological model.
"We are encouraged by the fact that at Pogo, veining can rapidly pinch and swell over minimal distances along trend and the same may be true of Tibbs," said Reda. "Do the newly discovered low-angle and the previously discovered high-angle veins at Tibbs have the economic widths and grades to make a mine? We do not know yet, but we are willing to take that bet and continue drilling to answer that question."
In addition to testing for low-angle veins, the 4,126-meter phase II program at Tibbs included reconnaissance drilling at the Galosh, Johnson Saddle, West Trench, and Wolverine targets.
At Galosh, RC drill holes spaced 600 meters apart were drilled into a 1,200 x 1,200-meter soil anomaly centered along a gneissic ridgeline 2,400 meters north of Gray Lead. Quartz vein-hosted mineralization was intersected in hole TBRC21-007, including 3.05 meters averaging 2.44 g/t gold from a depth of 164.6 meters. Hole TBRC21-008, drilled 600 meters east of TBRC21-007, cut 3.05 meters averaging 0.96 g/t gold from a depth of 19.8 meters.
Two holes, one RC and one diamond, were drilled at Johnson Saddle, a high-tenor gold and arsenic-in-soil anomaly hosted by gneissic rocks about 1,400 meters north of Gray Lead.
Tectonic geologists identified the potential for low-angle mineralized structures in the gneissic rocks to the west of a high-angle, northeast-trending controlling fault structure that lies adjacent to Johnson Saddle. Tectonic says the diamond hole, TBDD21-011, cut a package of west-dipping gneissic rocks with local intervals of amphibolite and thin slivers of altered ultramafic rocks, with low angle, west-dipping shearing, and faulting observed in multiple locations throughout the hole. Multiple intervals of gold mineralization were intersected in the diamond hole, including two meters averaging 1.61 g/t gold associated with bismuth and arsenic anomalism at a depth of 105 meters. RC hole TBRC21-009, drilled 50 meters to the east, cut 1.52 metes averaging 3.43 g/t gold.
Two diamond and three RC holes targeting prominent high-angle structures within a previously untested gold-arsenic-bismuth-antimony soil anomaly at West Trench were drilled during the phase II program.
Tectonic reports that drilling in the central portion of the target confirmed the presence of controlling high-angle fault structures adjacent to low-angle fractures and structurally controlled alteration zones. Results include 10 meters averaging 0.35 g/t gold from a depth of 240 meters in hole TBDD21-010; 1.4 meters averaging 1.25 g/t gold from a depth of 1.6 meters in hole TBDD21-009; 3.05 meters averaging 0.96 g/t gold from a depth of 109.7 meters in hole TBRC21-005, an overcut of hole TBDD21-010; and 4.57 meters averaging 0.31 g/t gold from a depth of 96 meters in hole TBRC21-006, the easternmost hole at the West Trench designed to drill beneath a 190.4 g/t gold quartz vein grab sample.
Specks of visible gold were noted within the TBRC21-006 interval during chip logging, prompting Tectonic to carry out metallic screen fire assays to ensure the "nugget effect" did not cause the gold to be underrepresented in the assay.
At the Wolverine target, hole TBDD21-008 drill tested a fault structure with coincident gold-in-soil and electromagnetic anomalies along a prominent air photo linear feature.
Altered granodiorite and diorite intrusive consisting of fault gouge and rubble was encountered for the entirety of the hole, with mineralization peaking at 0.65 g/t gold over two meters from a depth of 114 meters. Drilling at Wolverine by Tectonic and previous operators has yet to explain the source of a 600- by 1,200-meter high-tenor surficial gold and pathfinder element anomaly at this target.
The phase II program also included drilling at Tibbs South, an adjacent project leased from Doyon Ltd., where high-grade gold was found in rock samples collected during phase I 2021 exploration.
High-grade sheeted quartz-gold-bismuthinite veining similar to that observed at Kinross Gold Corp.'s Fort Knox Mine was found in granodiorite talus blocks along a 400-meter northeast-southwest trend at the Jorts target.
Grab rock samples collected at Jorts contained as much as 50.3 g/t gold, 904 parts per million bismuth, and eight ppm tungsten. Of the 44 samples collected from Jorts, 11 returned grades topping 20 g/t gold.
Rocks collected from Jeans Ridge, a prospect about 1,400 meters northeast of Jorts, returned grades as high as 7.9 g/t gold, 561 ppm bismuth, and four ppm tungsten. Of the 27 samples collected at Jeans, five had more than 1 g/t gold with elevated bismuth and tungsten.
Granodiorite-hosted gold mineralization associated with weak to moderate chlorite alteration and increased bismuth, tungsten, and tellurium was intersected in four of the five holes drilled last year at Jorts. Highlights include 6.1 meters averaging 0.44 g/t gold from a depth of 126.5 meters and 1.53 meters averaging 1.21 g/t gold from a depth of 169.2 metes in hole CCRC21-006; 1.53 meters averaging 1.79 g/t gold from a depth of 157 meters in hole CCRC21-008; and 6.1 meters averaging 0.33 g/t gold from a depth of 157 meters in hole CCRC21-009.
Four holes completed at Jeans Ridge cut gold mineralization variably associated with weak chlorite alteration and associated bismuth, tungsten, tellurium, and arsenic. A peak value of 0.50 g/t gold over 1.52 meters was intersected at a depth of 45.7 meters in hole CCRC21-004. Tectonic says the 2021 drilling did not explain the surficial anomaly, and further work is warranted.
Over his more than 16 years of covering mining and mineral exploration, Shane has become renowned for his ability to report on the sector in a way that is technically sound enough to inform industry insiders while being easy to understand by a wider audience.
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