Tower Resources Corners Bedrock Source of Nechako Gold Grain Dispersal Train
TSX VENTURE: TWR
Vancouver, British Columbia--(Newsfile Corp. - February 14, 2019) - Tower Resources Ltd. (TSXV: TWR) (OTCQB: TWRFF) ("Tower" or the "Company") is pleased to report that it has located the bedrock source area of the large gold grain anomaly that the Company identified two years ago (see June 18, 2017 press release) on its wholly owned Nechako property (Fig. 1) in south-central British Columbia, Canada, a 1.5-hour drive from Vanderhoof via the all-weather Kluskus-Ootsa road.
The Nechako property is 30 km northeast of New Gold's Blackwater gold deposit (8.62 Moz of Au resources at 0.88 g/t; New Gold NI-43-101 Technical Report, January 14, 2014) on the Interior Plateau where all but the highest hills are thickly covered by till and other glacial sediments that have historically hindered mineral exploration, leaving attractive opportunities for significant new discoveries.
Tower's latest discovery was made during a 13-hole, Phase II reverse circulation (RC) drilling program in December, 2018, approximately 1.5 km glacially up-ice from (i.e. west-southwest of; Fig. 2) the area that was covered in the 38-hole Phase I program in November, 2017 (see May 15, 2018 press release). A single, 245 m diamond core hole, No. NDH-18-006, was also drilled to test the Cu-Au potential of a large, thickly covered and pervasively argillic-altered (pyrite + chalky sericite) porphyry intrusion, the Blue Road Porphyry (Fig. 3), that was discovered in the Phase I program.
Both RC drilling programs were planned and managed by Overburden Drilling Management Limited (ODM) and employed the same type of RC drill that ODM used in the discovery of the producing Casa Berardi and Rainy River gold mines in Eastern Canada. This drilling system provides much more information than traditional top-of-bedrock sampling. Till horizons are sampled continuously from top to bottom and heavy mineral processing is used to recover and concentrate any glacially dispersed grains of gold, sulphides and other indicator minerals, thereby amplifying anomalies and enabling detection of overburden-covered mineralized zones located several kilometres up the ice flow path from the drill hole. The extracted heavy mineral concentrates (HMCs) are analyzed geochemically for Au, base metals and other elements of interest. The underlying bedrock is also drilled, sampled and analyzed, and a working geological map of the hidden bedrock surface is constructed (e.g. Fig. 3).
Background to the Phase II Drilling Program
The Phase II drill area is on the eastern foothills of a north-northwest trending ridge, the Nechako Range (Fig. 2). The earlier Phase I drilling was performed further east in an adjoining valley where the thickness of the till and other glacial deposits was found to range from 10 to 60 m (Fig. 4). Bedrock outcrops are very rare in this valley and uncommon even on the hills. Historical mineral exploration in the area relied primarily on soil sampling which was of limited value as the only mineralization that was detected was in small windows where the till is less than 1 m thick. Three such occurrences were discovered between 1969 and 1982 (Fig. 2), the large but very low-grade Chu porphyry Mo-Cu deposit atop the Nechako Range, the polymetallic April showing on the eastern slope of the range and the low-grade (0.1-0.2% Cu) C-zone porphyry Cu deposit on the edge of the adjoining valley.
Following glaciation, the valley was flooded by meltwater that deposited gravel over much of the till. The gold grain anomaly that Tower outlined in the valley in 2016 by sampling the limited till exposures (Fig. 2) is larger than and similar in strength to the gold dispersal train emanating from the large Blackwater gold deposit to the southwest (Fig. 1). However, the gold grains in the Nechako train are smaller and remain pristine along the length of the train rather than becoming progressively deformed, indicating that they were transported as small inclusions within protective sulphide mineral grains, then liberated in situ from these sulphides by post-glacial oxidation. This oxidation has penetrated only the top 3 m of the till and has not affected the sulphide grains at the depths sampled in the RC drill holes.
The Phase I drill holes in the valley revealed that the surface gold grain anomaly is actually a diluted secondary dispersal train produced by partial erosion, by the ice sheet that deposited the exposed till horizon, of a stronger primary train in an older, underlying, previously unknown till horizon rather than by direct glacial erosion of mineralized bedrock. The direction of ice flow and gold transport for this Lower Till was the same (east-northeast) as that for the Upper Till. The Lower Till and primary train are preserved only in deep drill holes that intersected glacially sheltered bedrock depressions (Fig. 4); in areas of thin cover they were completely eroded during the second ice advance.
As anticipated, the gold in the primary dispersal train is held within sulphide mineral grains, which are unusually abundant, rather than occurring as native gold grains. Unexpectedly, however, the train is polymetallic with Au, Ag, As, Cu, Zn and Pb all being significantly anomalous as in the high-grade Eskay Creek Au-Ag deposit in northern British Columbia. Notably, Au, As and Zn are distinctly more anomalous than Cu even though the dispersal train is directly down-ice from the C-Zone porphyry Cu deposit which contains negligible Au, As and Zn. The Cu content of the till HMCs matches the 0.1 to 0.2 Cu grade of the C-Zone, as is the rule for dispersal trains, suggesting that the Cu component of the train is derived entirely from this zone but the Au, Ag, As, Zn and Pb components have another source. The polymetallic mineralization of the April showing, 1.5 km further up-ice, is a close match. This showing is much too small to account for such a long, strong train but does provide clues to the probable location and orientation (southeast; Fig. 2) of the source of the train.
The 13 Phase II drill holes, Nos. NRC-18-39 to 51 (Fig. 3, Fig. 4), were designed to test the area between the dispersal train and April showing. The holes were drilled at 200 to 300 m spacing on three lines crossing the east-northeast ice flow corridor at 500 m intervals, with the first line located immediately up-ice of the C-Zone and the third line up-ice of the April showing.
Topographically, the drill area consists of a series of hills separated by narrow valleys (Fig. 2, Fig. 3). With the Phase I drilling demonstrating that the Lower Till horizon hosting the dispersal train is preserved only in areas where the overburden is thick (Fig. 4), the Phase II holes were preferentially sited in the valleys to increase the probability of intersecting this till horizon.
RC Drilling Results
Two of the thirteen drill holes intersected the western edge of the porphyry body that hosts the C-Zone Cu mineralization (Kluskus Road Porphyry; Fig. 3) and the others intersected a bimodal sequence of basaltic and dacitic volcanic and volcaniclastic rocks similar to those hosting the Eskay Creek deposit. The bedrock samples from three holes 500 m southeast along strike from the April showing, Nos. 39 to 41, contain arsenopyrite, a key indicator mineral for Au that was not encountered in any of the 38 Phase I drill holes.
Thick overburden sections containing the desired Lower Till horizon were intersected only in Holes 39 to 42 at the southwest corner of the drill area (Fig. 4). The HMC Au, Ag, As, Cu, Zn and Pb analyses for the Lower Till samples from these holes are listed in Table 1. The targeted up-ice extension of the polymetallic dispersal train is evident in the Lower Till at Hole 39 on the down-ice side of the arsenopyrite trend but the train is absent at Holes 40 and 41 on the up-ice side. Cu is not anomalous, confirming that the ubiquitous Cu in the segment of the dispersal train down-ice from the C-Zone in the Phase I drill area is derived entirely from this Cu zone.
The Au and Zn signatures of the anomalous Lower Till HMCs is Hole 39 are in the same 1000-1500 ppb and 2000-3000 ppm ranges, respectively, as in the Phase I segment of the dispersal train while the As content is stronger at 4000 to 5000 ppm. A stronger response for all three elements was obtained from the Upper Till HMCs in several shallower holes in the north-central part of the drill area where the second ice advance completely removed the Lower Till and directly glaciated mineralized bedrock. The HMCs of ten of the thirteen Upper Till samples collected from Holes 45, 47, 48 and 49 are significantly anomalous in Au, containing an average of 3480 ppb (maximum 9190 ppb) along with up to 34,800 ppm (3.48%) As and 6220 ppm (0.622%) Zn. Such strong anomalies are important because, as illustrated by the HMC Cu anomaly down-ice from the C-Zone, the grade of the till HMCs in a dispersal train tends to mirror the grade of the bedrock source mineralization. Moreover, the reported HMC analyses may understate the true grade of the dispersal train because only the -0.25 mm fraction of the HMCs was analyzed while the As and Zn minerals, arsenopyrite and sphalerite, are much more abundant in the +0.25 mm fraction. For example the 0.5 to 1.0 mm fraction of the Sample 03 HMC from Hole 45 contains 5% arsenopyrite and 7% sphalerite (Fig. 5), equivalent to 23,000 ppm As and 45,000 Zn, whereas the corresponding As and Zn analyses for the -0.25 mm fraction are only 6390 and 3520 ppm.
While the HMCs with the highest Au values tend to be anomalous in As, Au is not directly sympathetic to As indicating that, as in the similarly polymetallic Eskay Creek Au-Ag deposit, it may occur within one of the various pyrite phases observed in the HMCs rather than in the arsenopyrite.
In summary, the Phase II RC drilling clearly shows that the source of the polymetallic Au-Ag-As-Zn-Pb dispersal train in the Lower Till lies in the 500-m-wide gap between the second and third lines of drill holes. The similarly polymetallic April showing is located within the same gap but is so small that the till in Hole 44 down-ice from the showing is not anomalous. Historical diamond drilling on the showing was limited to three short holes (Fig. 3) totaling 150 m but did establish that the showing contains significant gold (e.g. 0.3 m of 1.4 g/t Au, 573.5 g/t (16.7 oz/t) Ag, 15.96% Zn and 15.83% Pb; 15.85 m of 1.25 g/t Au) and that the mineralization strikes southeast. The indicated larger mineralized zone at the head of the dispersal trend probably has the same southeast trend, and judging by the width of its dispersal train is approximately 700 m long with a possible 1 km extension southeast into the Phase I drill area where the dispersal train is shorter (Fig. 4) but similarly polymetallic. The Au grade of the till HMCs in the dispersal train is sufficient to suggest that the source mineralization is of a significant grade. Furthermore, the mineralized zone appears to be thick because the distal part of its dispersal train is up to 10 m thick and the main part of the train persists down-ice for at least 3 km, similar to the Blackwater train.
The RC drill remained on site following the Phase II drilling program. A small Phase III program totaling approximately 6 holes at an estimated cost of $50,000 is planned for late February. This drilling will be performed southeast along strike from the April showing to more precisely pin down the source of the Au-rich polymetallic dispersal train preparatory to a diamond drill test.
Diamond Drilling Results
Diamond drill hole NDH-18-006 was designed to test a 500 m long IP chargeability anomaly that is coincident with the newly identified and persistently argillic-altered Blue Road Porphyry (Fig. 3). All of the Phase I RC drill intercepts from the top of the porphyry contained significant pyrite. The IP anomaly suggested an increase in pyrite content at depth and potentially also a change from argillic to potassic alteration with attendant Cu ± Au mineralization.
The diamond drill hole intersected feldspar porphyry to 120 m followed by intermediate volcanic and volcaniclastic rocks to the end of the hole at 225 m. Disseminated and fracture-controlled pyrite occurs at the 1-10% level throughout the hole. A 12.0 m interval of the volcanics from 130 to 142 m, below the porphyry contact, assayed 0.05 gpt Au, 13.6 gpt Ag, 0.02% Cu, 0.09% Pb and 0.26% Zn (Table 2), including 6.0 m of 0.11 gpt Au, 10.5 gpt Ag, 0.01% Cu, 0.22% Pb and 0.57% Zn. Although these results are not of economic interest they do demonstrate potential for significant Au-Ag-Pb-Zn mineralization proximal to Blue Road Porphyry.
In the RC drill holes, ODM collected samples weighing approximately 12 kg from all till sections, typically over 1.5 m intervals. One or more bedrock samples were collected over the same interval. A heavy mineral concentrate (HMC) was extracted from the -2 mm matrix of each till sample at ODM's mineral processing laboratory in Ottawa, Ontario, and all recovered gold grains were individually measured and classified by morphology.
The till HMCs and bedrock samples were analyzed by Activation Laboratories Ltd. (Actlabs) at its ISO 17025 accredited geochemistry lab in Ancaster, Ontario for a multielement suite including Au, Ag, As, Cu, Zn and Pb using a combination of Induced Neutron Activation (INA) and ICP/MS methods. Field duplicates were used to monitor the quality of both ODM's heavy mineral separations and Actlabs analyses. Also, by using INA analysis, most of the HMC was preserved allowing post-analysis visual inspection and check analysis if required.
The diamond drill hole was logged by Tower and split core samples, generally 2 m in length, were prepared at Tower's core logging facility located on site at the Nechako property and shipped to Actlabs' ISO 17025 accredited geochemistry lab in Kamloops, BC. Samples were analyzed for gold by fire assay and ICP-OES and for 37 other elements, including copper, using a four-acid, near-total digestion. QA/QC samples including blanks, standards and duplicate samples were inserted regularly into the sample sequence at a ratio of approximately 1:15.
National Instrument 43-101 Disclosure
The technical content of this news release has been reviewed and approved by Mr. Stuart Averill, Chairman of ODM, a Director of the Company and a Qualified Person as defined by National Instrument 43-101.
About Tower Resources
Tower is a Canadian based mineral exploration company focused on the discovery and advancement of economic mineral projects in the Americas. The Company's key exploration assets are the Rabbit North copper-gold porphyry project located between the New Afton and Highland Valley Copper mines, the Nechako gold project near New Gold's Blackwater project and the More Creek and Voigtberg gold projects in the Golden Triangle area of Northern British Columbia.
On behalf of the Board of Directors,
Tower Resources Ltd.
Gerald Shields - Chairman
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Figure 2: Locations of the RC drill holes relative to the gold grain anomaly identified at the surface of the till in 2016
Figure 3: Geology of the covered bedrock surface as determined from RC drill holes
Figure 4: Thickness of the glacial deposits and subsurface limit of the partially eroded Lower Till horizon and Au-Ag-As-Zn-Pb (±Cu) dispersal train
Figure 5: Binocular microscope photograph of part of the coarse 0.5-1.0 mm fraction of the HMC from the third Upper Till sample in Hole 45