Geology & Mineralization
The currently known gold deposits at Back River are comprised of Umwelt, Llama, Goose, Echo and Nuvuyak (all on the Goose Property), and the George deposits approximately 50 km to the north of the Goose Property. The Goose and George deposits are historical deposits which formed the resource basis upon which Sabina acquired the property in June 2009.
Most of the known or observed gold mineralization identified on the Back River Project is associated with quartz veins, silicification and shearing. The mineralization occurs within silicified and variably sulphidized iron formation and to a lesser extent sedimentary units that appear to have a spatial association with narrow porphyritic felsic dykes and mudstones. Sulphide minerals observed on the Back River Project include pyrite, arsenopyrite, and pyrrhotite. Sulphide mineralization may be associated with accessory chlorite, carbonate, hornblende and grunerite. Visible gold is locally present, especially when sulphides are greater than 10% and when coarse-grained arsenopyrite is present.
On the Goose Property, gold mineralization on the Goose deposit is predominantly structurally controlled. The deposit is situated within the lower iron formation and underlying sediments beneath the Goose antiform structure, which resides within a 500m + wide corridor of widely spaced, subparallel north to northeast trending southeast dipping, normal faults that have up to 30 m of left-lateral displacement and a down dropping of individual fault blocks of up to 75m. The Umwelt and Llama deposits are underlain by similar geology to Goose. Suphidized oxide and silicate facies banded iron formations are cut by felsic and gabbroic dykes. Airborne and ground magnetics suggest that the iron formations are strongly folded. Recent drilling at Llama confirms the complexity of the structural history of that area, but tighter drill spacing in 2012 is allowing a continuous high grade gold bearing antiform structure to be defined.
Gold mineralization at George is located within oxide iron formation near the stratigraphic base of this unit. Less significant gold mineralization is also hosted within silicate iron formation. Gold bearing zones are associated with sulphide concentrations in the iron formation and are commonly accompanied by increased quartz veining and attendant alteration of the surrounding rocks.
For further details on the geology and mineralization of the Back River Project please see the Company’s latest AIF and NI 43-101 report available in the Public Filings section of this website.
In 2018 and 2019, exploration work at the Goose property has focused on new discovery and resource extension and optimization at the Goose Main, Umwelt, and Llama deposits, the new Nuvuyak discovery and to a lessor extent the Echo Deposit.
This work was undertaken with the objectives of further improving the economics and life span of future mine operations. Throughout this time period, exploration drilling successfully discovered mineralization extending over an additional 25% of plunging iron formation. Between the Llama Extension and Nuvuyak zones, Sabina identified an additional combined 950 m of gold mineralized iron formation along plunge from known deposits. Additional work and evaluation will be required to better understand the impact of these new potential mineral resources to the project, but it is likely that the current mine life (as outlined in the Sept 2015 43-101 feasibility report) will be significantly extended.
The 2018 exploration programs at the project consisted of two drilling programs completing approximately 22,500 m. The spring drill program, running from March to May, drilled 6,000 m, where the summer drill program completed 16,500 m from July to October. In addition, exploratory field work consisted of geological mapping and rock and till sampling on the Goose and Boulder properties during the summer field season.
The 2019 exploration programs at the project consisted of a spring drilling program and a summer trench mapping program. During the spring program, running from April to June, 6,467 m were drilled on the Goose property. The summer field program focused primarily on mapping the re-excavated and extended historic (2004-2005) trenches over the Goose Main deposit with additional small field work excursions at the Del and Goose properties.
Table 1: Exploration Spending 2018 and 2019
||Field Work Completed
||22,500 m in 40 drill holes. Majority at Goose Property with additional scout holes at the Boulder Property
||Geologic mapping, prospecting, till sampling, structural study, age dating study, deposit modelling updates, surficial geology study
||6,468 m in 8 drill holes. All drilling at the Goose Property
||Geologic mapping, rock sampling, trenching, structural study, and geophysical compilation
Figure 1: Idealized long section of the 8 km long Goose Property gold complex showing approximate strike lengths of mineral zones and possible extensions for targeted growth towards 10 million gold ounces
Key advancements in resource optimization, discovery, and geoscience include:
- The significant extension of the Llama underground gold structure. Mineralization from the bottom of the Llama open pit reserve now extends for greater than 1,200 m down plunge. Recent successes include the extension from the existing Llama underground resource (which is not in the current development plan) adding an additional plunge length of approximately 580 m, as well as the discovery of higher-grade mineralization over numerous drill holes within this plunge extension. The mineralizing structure at Llama underground remains open to depth.
- The new discovery of a significant zone of gold mineralization, the Nuvuyak Zone, located approximately 1,000 m west of the Goose Main deposit. The Nuvuyak gold zone has now been tested by 14 drill holes which confirm a strongly mineralized, folded iron formation package over a plunge extent of 370 m, open both up and down plunge. The Nuvuyak gold zone is analogous in size and mineral robustness to the other Goose deposits and is the most important discovery since the Umwelt discovery in 2010.
- The definition and expansion of a thickened, high grade corridor of mineralization within the Umwelt underground, initially at the Vault Zone and more recently in the up-plunge direction. Recent drilling and modelling show that the high-grade zone or corridor extends through Vault, up and down plunge with excellent potential for significant optimization through additional drilling. Early development of the Umwelt underground has the potential to add over 80,000 ounces a year of gold production to the Back River gold deposit.
- Key components of relevant data sets have been integrated into a 3D platform to facilitate construction of a robust geological model that has greatly enhanced the ability to interrogate, review and prioritize exploration targeting. Some of the key outcomes include: a better understanding of ore controls, a stronger and more detailed model of all important stratigraphic units, a better understanding of key structural components and the effect on iron formation and ore deposit geometry, and a better understanding of gold distribution and related mineralogy.
Description of Currently Defined Goose Project Advancement Through Recent Drilling and Discussion of Resource Opportunities
Llama Underground - Llama Extension
The Llama Deposit contains an estimated 3,557,000 tonnes at 6.50 g/t Au for 743,000 ounces of gold in the Measured and Indicated categories, and an additional 295,000 tonnes at 6.77 g/t Au for 64,000 ounces of gold in the Inferred category. Of this, 1,749,000 tonnes at an average grade of 7.15 g/t Au for 402,000 ounces in the Proven and Probable categories make up the open pit Reserve. The current Feasibility Study does not contemplate an underground development at Llama. Exploration at Llama in 2017 aimed to test the down plunge continuity of the deposit, successfully returning significant high grades such as 9.48 g/t Au over 38.55 m in drill hole 17GSE516B and 15.67 g/t over 23.25 m in drill hole 18GSE530. To date 15 drill holes have extended the gold mineralization shell down plunge from the Inferred Mineral Resources (outside of the open pit shell) by approximately 580 m with grades and thicknesses greater than those intersected in the current Llama underground Resource. This drilling has extended the total “outside” of the pit gold mineralization at Llama to over 1,200 m of strike extent and it remains open to depth.
Current combined Measured, Indicated and Inferred Underground resources total 1,160,000 tonnes at 7.94 g/t Au for 295,000 ounces.
Figure 2: Llama long section showing current resource and reserves in red and the new Llama Extension mineral zone in green with recent drilling and select significant gold intercept values
The Nuvuyak Zone was discovered in 2018 with drill hole 18GSE545 that returned 11.58 g/t Au over 39.50 m. The mineral zone which is located approximately 1,000 m down plunge of the Goose Main deposit has now been drilled over 370 m of plunge length in 14 drill holes and exhibits many of the geologic and mineralogic characteristics of the existing Goose property deposits; Llama, Umwelt, and Goose Main. The deposit is open both up and down plunge, as well as in the down dip direction along the limbs of the anticlinal fold. Examples of select significant intervals from recent Nuvuyak drilling include; drill holes 18GSE559W1 which returned 12.41 g/t Au over 8.70 m, 18GSE558 which returned 16.39 g/t Au over 13.20 m, 18GSE558W2 which returned 5.81 g/t Au over 34.60 m and 19GSE566 which returned 10.04 g/t Au over 18.00 m.
Figure 3: Nuvuyak Zone discovery mineral zone with drill holes and modeled iron formation interpretation
Figure 4: Goose – Hook – Nuvuyak unfolded and idealized long section showing gold structure connection to the Goose Main deposit and high grade nature of many of the Nuvuyak discovery and follow-up drill hole values
The Nuvuyak geometry, fold amplitude, extensive strike length of the mineralized structure, considerable thickened iron formation in the hinge zone, and axial planer positioning of the felsic dyke/mineralizing structure allow for preliminary positive modelling and scoping of a large-scale mineral zone. To date current drilling at Nuvuyak shows a higher than Back River average grade of 7.86 g/t.
High Grade Corridor - Umwelt Underground
The underground portion of the Umwelt Deposit that is planned for development currently hosts an estimated 3,491,000 tonnes of 7.38 g/t for 829,000 ounces of gold in Proven and Probable Reserves. The underground mineral structure is contiguous with that of the open pit which hosts 2,668,000 tonnes of 6.49 g/t Au for 557,000 ounces of gold in Proven and Probable Reserves. Exploration at Umwelt since the Mineral Resource Estimate in October of 2014 has focused on targeting a higher grade and thickened host rock corridor demarked by a Quartz-Feldspar Porphyry (QFP) intersection with the Lower Iron Formation (LIF). The Vault Zone is situated along the QFP-LIF intersection at depth, and drilling during 2018 and 2019 illustrated that the exceptional high grade and thick intersections seen at Vault are present up-plunge from the Vault Zone; drill hole 18GSE532 returned 8.38 g/t Au over 11.45 m and drill hole 19GSE569 returned 14.97 g/t Au over 21.75 m. These recent drill intercepts suggest an opportunity to improve the current grades and thicknesses within the existing Mineral Resources at Umwelt.
Figure 5: Umwelt Underground and Vault zone drilling with highlighted high grade intercepts
Additional down plunge opportunity is significant and untested by drilling where the Umwelt structure remains open. There is a strong opportunity to increase the high grade mineralization within the existing resource along the QFP/LIF intersection up-plunge from Vault and along the upward plunge of the intersection towards the open pit. The more recent drilling has given confidence to the concept that the iron formation and mineralization is thicker and higher grade near this central QFP/LIF intersection which provides significant opportunity to impact the resource.
To properly scope the higher grade and thicker mineralized intersections within an approximate 100 m wide corridor in the prospective area would require approximately 6,500 m of additional drilling. The proposed optimization drilling (yellow stars) is indicated in Figure 6 below.
Figure 6: Umwelt Long Section Showing High Grade Corridor and Planned Drilling
Geology and Exploration Targeting Advances
Several field programs and geoscience initiatives were undertaken at Back River between 2018 and early 2020 to complement the drilling programs and further advance new target generation, target testing, and mineral system/ore deposit understanding. The geoscience initiatives were detailed studies contributing to a broad mission of establishing the structural evolution and the paragenesis of gold mineralization with a primary goal of improving regional exploration criteria. Initiatives included: reconnaissance drilling, focused oriented core audits and structural data review, geological mapping and rock sampling, trenching and detailed structural mapping, targeted structural studies, quaternary mapping and till sampling, and age dating studies of key host rocks and prominent sulphide minerals.
The strong focus on geoscience and detailed observation resulted in several products and recommendations that have improved and aided in the updating of the Goose property stratigraphy and structural model. All data sets have been integrated to some degree into a 3D platform to facilitate construction of a robust geological model that has greatly enhanced the ability to interrogate, review and prioritize exploration targeting. Some of the key outcomes include; a better understanding of ore controls, a stronger and more detailed model of all important stratigraphic units, a better understanding of key structural components and the effect on iron formation and ore deposit geometry, and a better understanding of gold distribution and related mineralogy.
Figure 7: Goose property iron formation modelling, deposit mineralization and select targeting locations
The development of this multi-focus approach and integrated 3D exploration model along with a comprehensive target-log book and re-defined exploration tool box has allowed the exploration team to advance a number of priority targets including opportunities; outside the conventional iron formation host rock, targets extensional to defined ore bodies, and higher grade resource optimization targets within ore bodies at the Goose property.
Evidence of the success of this approach is highlighted by the discovery of Nuvuyak a mineral zone fast approaching 1,000,000 oz in scope, the identification and expansion of a high grade corridor within the Umwelt underground and the large drilling step-outs that resulted in the significant extension of the Llama underground deposit.
The increased understanding of gold mineralization controls at the Goose property and the geological evolution of the Back River basin continues to be evolved. With better understanding and incorporation of these new understandings and continued refined exploration methods Sabina has increased potential for success in future exploration through the Back River gold complex.
A planned 8,500 meter drill program will target additional high grade potential at Umwelt, infill and plunge extension at Llama and other new high potential exploration targets within the 8km Goose Property gold complex. An initial focus will be at Umwelt to test the high-grade underground corridor continuity up plunge from Vault towards the bottom of the planned open pit. Exploration will also commence infill drilling at Llama with the objective of extending resources from the bottom of the current Llama underground resource model, further down plunge and potentially beyond the limits of recently established mineralization intercepts.
An additional focus of drilling will be the testing of a select number of new exploration targets. These targets have been identified through an intensive re-evaluation of the exploration model leading to a target ranking exercise based on potential impact and prospective geological characteristics. The exploration team continues to strongly review and improve its understanding of the gold mineralization system to strengthen the ability to find new gold zones but also to help define and trace high grade structures within known deposits. Exploration targeting will be supported and advanced by a field program that includes an airborne geophysics survey, trenching , rock sampling and mapping.