The Barrow Creek Lithium Project covers an area of 278km2, located in the highly prospective Northern Arunta Pegmatite Province of Central Northern Territory.
The Barrow Creek Lithium Project is considered highly prospective for hard-rock Lithium-Tin-Tantalum (Li + Sn + Ta) mineralisation and is adjacent to tenements held by Core Lithium Limited (ASX: CXO) and Lithium Plus Minerals Limited (ASX: LPM). The Northern Arunta Pegmatite Province has been described as one of the largest pegmatite provinces in Central Northern Territory.
During the Quarter ended 31 March 2022, the Company announced that the Exploration Licence, EL 32804, which encompasses the Barrow Creek project had been granted by the NT Mines Department for an initial period of 6 years.
The Company has recently submitted its mine management plan and exploration permits to enable RC drilling to commence in the NW project area and is currently working with the Aboriginal Areas Protection Authority (AAPA) to obtain an authority certificate for the proposed drilling campaign per standard exploration requirements.
Exploration to date has been very successful with initial reconnaissance work highlighting the fertility of the pegmatites at Barrow Creek in the NW project area. The Company has also subsequent to the end of the Quarter ended 31 March 2022 conducted a mapping and sampling campaign on the SE project area and is currently planning to mobilise a team to commence a similar mapping and sampling campaign at the SW project area where no work has previously been conducted.
The figure below depicts a satellite location map of the Barrow Creek Lithium Project as well as surrounding projects owned by Core Lithium Limited and Lithium Plus Minerals Limited:
Figure 1: Satellite image location map of the Barrow Creek Lithium Project, Northern Arunta Pegmatite Province of Central Northern Territory
The BCL Project is surrounded by Core Lithium Limited (ASX: CXO) and Lithium Plus Minerals Limited (ASX: LPM) and is proximal to several known Lithium-Tin-Tantalum occurrences, sharing similar geological settings with the BCL Project. Highly fractionated pegmatites have been mapped and documented in government reports in this region. Although limited exploration has been undertaken on the BCL Project area, the project’s location, together with the numerous mineralised occurrences and workings located nearby, point to the significant exploration upside that exists at the BCL Project.
The pegmatites of the Barrow Creek Pegmatite Field have yielded historic discoveries of Sn-Ta-W, however, before investigation by government geologist Frater (2005), no historical exploration had considered the potential for Lithium (Li) mineralisation. Geochemical analysis by Frater (2005) strongly points to Lithium-Caesium-Tantalum (L-C-T) Type pegmatites in the Barrow Creek Pegmatite Field. Swarms of pegmatite dykes and sills are related to the Ooralingie and Bean Tree granites of the Barrow Creek Granite Complex (~1803 Ma; Smith 2001).
Hyperspectral Remote Sensing Survey
During the Quarter ended 31 March 2022, the Company completed a Hyperspectral Remote Sensing Survey at the Barrow Creek project. The Hyperspectral program used Sentinel-2 satellite longwave infrared (LWIR), visible/near-infrared (VNIR), and shortwave infrared (SWIR) imagery for interpretation across the Barrow Creek Lithium Project.
The results were most encouraging, and multiple high priority exploration targets were identified. The hyperspectral targets were generated by interrogating known associated minerals of LCT pegmatites, known as endmembers, like Phlogopite (Mica), Orthoclase (Feldspar) and others. This analysis resulted in the generation of mineralisation target maps. These maps (relative abundance) were then compared with known Tantalum (Ta) occurrences to validate their ability to identify the Tantalum occurrences, which share the same LCT pegmatite lithology that are known to host Lithium mineralisation. As a result, the target maps generated were based on known geological signatures derived from nearby known Tantalum occurrences, thereby increasing the confidence on the exploration targets.
The Tantalum occurrences were successfully identified, supporting the use of these endmember maps to identify high potential LCT pegmatite locations and targets within the Barrow Creek Lithium Project. Swarms of pegmatites occur 15 km north of Barrow Creek and directly west of the Stuart Highway in the Northern Territory.
The pegmatites contain Lithium, Niobium, Tantalite, Columbite and Cassiterite Pegmatite is an igneous rock composed predominantly of quartz, feldspar and mica. The Hyperspectral review mapped the Barrow Creek area by mica (phlogopite) and orthoclase abundance in the regolith and revealed that the known Tantalum (Ta) occurrences occur on mica anomalies. This knowledge demonstrates and supports that the mica anomalies identified within the Barrow Creek Lithium Project are high priority exploration targets.
The orthoclase hyperspectral abundance map supports the characteristics identified by the phlogopite maps. Combining these two endmember maps proved helpful in identifying potential Lithium exploration targets on the Barrow Creek Lithium Project. The multivariate statistical technique of linear discriminant function analysis was also used to generate a single abundance map, trained by using the spectral abundances of the Tantalum occurrences. The classifier was driven (in order of importance) by phlogopite, orthoclase, magnetite, illite, rhodonite, celestite and hematite and generated several high-priority exploration targets as set out in the map below.
Figure 2: Hyperspectral target exploration map. High priority targets are shown in yellow
Initial Reconnaissance Exploration
The field reconnaissance sampling program completed during the due diligence phase of the Barrow Creek Lithium Project acquisition has yielded highly encouraging results with anomalous lithium, tantalum, caesium, niobium and rubidium in samples collected from the outcropping pegmatites.
The program focused on the NW of the project and identified a mineralised zone of 950m x 500m which remains open in all directions and where multiple LCT-type pegmatites were identified.
Assay results from initial reconnaissance sampling have confirmed the presence of fertile LCT pegmatites at Barrow Creek and produced results of up to 817ppm Li2O, demonstrating the fertility of the LCT pegmatites and warranting further systematic exploration of the area. Identifying LCT pegmatites as well as the shared elevated Lithium content of the samples (refer to Table 1) is highly encouraging. The highest Lithium assays (387ppm-817ppm Li2O) are from seven samples that were collected over a strike distance of 950m and from two interpreted north-west trending pegmatite dykes (refer to Figures 3 and 4). The presence of these Lithium-rich pegmatites are significant and warrant further work.
The map below illustrates the location of the samples that were collected:
Figure 3: Sample location map from the reconnaissance field program at the Barrow Creek Lithium Project. Lithium results are shown as Li ppm, which convert to Li2O by a factor of 2.15 per industry standard
Sampling has also demonstrated elevated results for Caesium (Cs), Tantalum (Ta), Rubidium (Rb) and Niobium (Nb), which are important trace elements in the LCT pegmatite structures. The enriched pegmatites are considered part of zoned LCT pegmatite swarms, and exploration is ongoing to identify more extensive Lithium-rich outcrop and areas.
Lithium-caesium-tantalum (LCT) pegmatites are the class of rare-element pegmatites that host the major hard-rock Lithium and Tantalum deposits in Western Australia, including Greenbushes, Pilgangoora and Wodgina. The pegmatites develop from differentiated granitic magmas that in addition to the LCT elements are also commonly enriched in niobium (Nb), beryllium (Be), rubidium (Rb), and tin (Sn). As a function of the differentiation process a spatial zonation of the rare-element assemblages is often present within the pegmatites with a progressive increase of Ta, Li, and Cs concentrations with increased granite differentiation.
The positive results from this program warrant an accelerated and more focused exploration effort that will include detailed surface sampling and mapping and the design of an inaugural RC drilling program.
The table below summarises the assay results received from the reconnaissance field program.
Table 1: Summary table of the Barrow Creek assay results
The results from the reconnaissance field program were also compared to the recently completed Hyperspectral Survey. A high correlation exists between the outcrops with anomalous lithium values and those highlighted by the Hyperspectral Survey, providing the Company with a higher degree of confidence that the additional targets identified from the Hyperspectral Survey, remain high-priority exploration targets.
These additional target areas are outside of the zone which was discretely sampled during the reconnaissance program and remain untested, highlighting the significant exploration upside and potential of the Barrow Creek project.
The map below illustrates that assay results overlaid by the Hyperspectral Survey data.
Figure 4: Sample location map from the reconnaissance field program at the Barrow Creek Lithium Project. Lithium results are shown as Li ppm, which convert to Li2O by a factor of 2.15 per industry standard. Hyperspectral Survey data is also illustrated for correlation purposes
Phase II Exploration Program
The second phase exploration program followed up and expanded upon areas identified as fertile pegmatite zones from samples collected during the initial reconnaissance program. The results from the phase one program included lithium mineralisation up to 817ppm Li2O. In addition, target areas highlighted through the Aster based hyperspectral survey identified high-priority targets which were tested during the Phase II exploration program.
The program targeted all pegmatite outcrops in the north-eastern part of the tenement. At the same time, soil samples were collected from all granite derived soils where outcrops were not available. Combining these results will help the Company determine geochemical signatures to be used for target vectoring for the proposed inaugural drill program on the project, anticipated to commence as early as Q2 of 2022, subject to receipt and interpretation of the assay results from this Phase II campaign.
The area covered by the second phase of work measures 8km x 6km and is shown in Figure 5 (below). The Hyperspectral anomalies are also highlighted.
Figure 5: High-priority exploration target area at the Barrow Creek Lithium Project, NT
An example of pegmatoidal veins and dykes is shown in Figure 6.
Figure 6: Image depicting some of the pegmatite veins and dykes encountered on the Barrow Creek Lithium Project
The initial reconnaissance field program identified elevated results for Caesium (Cs), Tantalum (Ta), Rubidium (Rb) and Niobium (Nb), which are essential elements in LCT pegmatite fertility and warranted an accelerated and more focused exploration effort.
The design for the Phase II exploration program was to focus on those areas that had already been identified as having fertile LCT-Type Pegmatites and increasing the sample density in that area and its immediate surroundings. Reconnaissance sampling conducted by the Company previously identified a zone measuring 950m x 500m in the north-eastern extent of the project. The results from those samples indicated several fertile LCT-Type Pegmatites based on lithium and trace element grades.
The focus area has been expanded significantly, now measuring 3.8km x 4.8km where systematic rock and soil sampling was conducted during this Phase II campaign.
An additional high potential area remains untested in the southeast of the project which will be tested in a similar manner as soon as possible.
Soil samples were collected in areas where the soil demonstrated an original granite origin and are believed to be in situ, meaning they are believed to have formed from a granite/pegmatite originally located in that area. In some areas, the soils were clay based alluvial and colluvial sediments and samples were not collected in these areas. Samples were collected in lines spaced about 400m apart, with individual samples being collected at 50m intervals along the lines. A total of 350 soil samples were collected in this manner.
The soil sample grid, represented by blue dots is depicted in Figure 7 below.
Figure 7: Figure depicting the phase two soil sample locations collected on the Barrow Creek Lithium Project, Northern Territory
A total of 119 rock samples were also collected in the target area, with the majority focusing on the north-eastern portion of the project. The rock samples were collected by inspecting all rock outcrops in the area. If pegmatitic veins or dykes were identified, samples were collected on those outcrops. Rock outcrops became less prevalent toward the west of the target area. However, soil samples collected over the area is intended to provide insight into the rocks below the cover.
The rock sample locations, represented by red dots is depicted in Figure 8 below.
Figure 8: Figure depicting the phase two rock sample locations collected on the Barrow Creek Lithium Project, Northern Territory
Figure 9: Depicts an example of another pegmatite outcrop sampled during the second phase of field work.