Yarawindah Brook Project (80% interest)
- Exciting new PGE-Ni-Cu frontier driven by the success of Chalice Mining at the neighbouring Julimar Project
- Large landholding in the region (>400km) and an early mover into the district
- Encouraging results to date, with minimal effective exploration conducted
- Prospective geology and near-surface occurrences of nickel and copper mineralisation
- Exploration programs underway, generating new data and targets
The Yarawindah Brook Project is located ~100km northeast of Perth, in the emerging PGE-Ni-Cu sulphide New Norcia province. The Project comprises a significant ground position of over 400km2, approximately 40km north from Chalice Mining’s discovery of the high-grade Gonneville PGE-Ni-Cu deposit.
The New Norcia region is deeply weathered, with little fresh rock outcrop and extensively covered by cultivated farmland. Despite the presence of known Ni-Cu occurrences, discovered in the 1970s, most historical exploration has focused on surficial bauxite deposits. As a result, there is limited deeper, bedrock drilling and the geology is poorly understood. Historical exploration focused near-surface platinum and palladium (PGE) mineralisation which Caspin considers to be indicative of a large basement sulphides deposit of PGEs including nickel and copper.
These elements are critical components of advanced battery and electrical technology. Caspin is therefore well placed to benefit from global trends towards electrification and decarbonisation.
Yarabrook Hill is a new PGE target identified after review of historical exploration for sulphide PGE’s, beneath oxide mineralisation striking over 2km at surface. The Prospect was the focus of limited PGE exploration during the 1970’s and 1980’s, following the discovery of surficial deposits of palladium and platinum within lateritic rocks. Several drill programs identified supergene mineralisation at shallow depths, but rarely explored deeper than the weathered zone, nominally below 50m vertical depth.
Phase 1 of an RC program was completed in August through September 2021. The program consisted of 11 holes for approximately 3,000m of drilling as a first pass test of the Yarabrook Hill intrusion, with the aim being to provide early insight into the architecture of the intrusion and assist any subsequent programs in vectoring towards its most prospective parts.
Results from the Phase 1 drilling returned broad zones of mineralisation including a standout intersection from YARC0001 of 263m @ 0.24g/t Pd+Pt+Au (3E), 0.11% Ni & 0.13% Cu (see ASX announcement of 24 January 2022). Further broad zones were returned in YARC0009, including 116m @ 0.11g/t 3E, 0.15% Ni & 0.11% Cu, hosted within peridotite and pyroxenite rocks. Note that these intersections contain some internal dilution from rocks such as late-stage, barren dolerites. YARC0009 was drilled 135m up dip of YAD0017 which previously intersected multiple zones of PGE-Ni-Cu sulphide mineralisation (see ASX announcement of 5 July 2021).
Phase 2 consisted of a further 16 RC holes (~2,500m) and two diamond drill holes (YARCD0012, YAD0019; ~1,500m). The RC program mostly tested targets at the Eastern geochemical soil anomaly (5 holes, YARC0017 – YARC0021) and XC-22 airborne electromagnetic anomaly (6 holes; YARC0024 – YARC0027). Three holes (YARC0013-YARC0015) tested a magnetic feature to the south of Yarabrook Hill but only intersected barren lower sequences of the intrusion.
Results from YAD0019 and the diamond tail of YARCD0012 received showed broad zones of PGE, nickel and copper anomalism with narrow higher-grade zones, as predicted from visual observations. Anomalous PGE, nickel and copper mineralisation was returned over widths of 120m and 123m respectively. YAD0019 was a deep stratigraphic diamond hole, part-funded by the WA government Exploration Incentive Scheme, designed to provide a better understanding of the Yarabrook Intrusion architecture rather than directly targeting economic mineralisation (Figure 2).
The Central Yarabrook Hill mineralised zone strikes over at least 2km and remains relatively under-explored, with large gaps of up to 500m without any significant drilling beyond 100m depth. Therefore, further interpretation and understanding is warranted.
Significant Nickel, Copper and PGEs at Serradella Prospect (previously named XC-22 Prospect)
Drill hole YARC0022 was the first hole to test an AEM anomaly (XC-22) at the northern end of Yarabrook Hill and intersected a sulphide zone over 60m thick from immediately beneath the fresh rock interface, only 46m down hole (see ASX announcement of 9 February 2022).
Two significant zones of mineralisation were encountered. A semi-massive sulphide zone from 46m downhole returned assay results of 2m @ 1.42% Ni, 0.47% Cu and 0.33g/t 3E (Pd+Pt+Au), hosted within a mafic pyroxenite-gabbro rock. This is a significant result at this shallow depth and appears to be coincident with the Serradella airborne electromagnetic (AEM) anomaly.
The 68m mineralised interval also included a zone of significant low-sulphide, but PGE-rich mineralisation. Subsequent re-assaying for the full six element PGE-suite (iridium (Ir), osmium (Os), rhodium (Rh) and ruthenium (Ru), as well as platinum and palladium) returned significant rhodium mineralisation up to 465ppb, grading 13m @ 0.17g/t Pd, 0.74g/t Pt, 0.11g/t Rh, 0.26% Ni, 0.21% Cu from 101m. This intersection included a high-grade interval of 2m @ 0.40g/t Pd, 2.45g/t Pt, 0.41g/t Rh, 0.23% Ni, 0.09% Cu from 112m. When adding the minor gold contribution, this can be expressed as 13m @ 1.08g/t 4E, 0.26% Ni & 0.21% Cu, including 2m @ 3.29g/t 4E, 0.23% Ni & 0.09% Cu, which at this depth the Company considers to be very significant (Figure 3).
This lower zone has a clear stratigraphic control, occurring at the lower contact of the mineralisation-hosting pyroxenite-gabbroid unit with underlying peridotite.
This lower PGE-rich horizon correlates well with the mineralisation (3m @ 1.04g/t Pt, 0.50g/t Pd) in historical drill hole YBR063 and likely supergene mineralisation intersected near surface in YBR060 – YBR062. This stratigraphic correlation is supported by both these intersections having distinctively high Pt/Pd ratios.
Since first identifying significant mineralisation at the Serradella Prospect in November 2021, the Company has drilled a further 18 holes, stepping-out along strike and down-dip from the discovery hole, YARC0022. The Company has used magnetic imaging to map the prospective contact zone between upper pyroxenite (mafic) and lower peridotite (ultramafic) units which hosts the PGE-Ni-Cu mineralisation. The magnetic anomaly has a strike length over 1.2km long and is open down-dip, plunging to the northeast (Figure 4).
Several RC holes that originally failed to reach target depth have been extended with diamond tails. Diamond tails have been completed for YARC0025 and YARC0027, however YARC0024 was unable to be re-entered and extended. A new diamond hole, YAD0020 was completed as a replacement, which drilled through a thick late-stage dolerite dyke at the approximate position where the bulk of mineralisation would have been expected. As a result, only minor zones of peridotite and pyroxenite with associated sulphides have been observed.
Diamond tails on YARC0025 and YARC0027 (from here referred to as YARCD0025 & YARCD0027) have intersected significant zones of sulphides, approximately correlating with mineralisation intersected in YARC0022 (see ASX Announcement 2 May 2022 – for Table of lithologies intersected). All assays remain pending.
It should be noted that PGE-rich mineralisation in YARC0022 is not always associated with significant sulphides, sometimes being associated with less than 3% sulphide. The presence of sulphides is considered a useful indicator of the potential presence of PGE-mineralisation, but the amount of sulphide does not necessarily correlate with the tenor of PGE mineralisation.
In addition to these diamond holes, a total of 16 RC holes have been drilled on broad spacings across the magnetic anomaly at Serradella, designed to test the continuity of PGE mineralisation at the prospective pyroxenite – peridotite contact, along strike and down-dip. This target contact has been successfully intersected in all drill holes and appears to have defined a consistent mineralised horizon over a strike of at least 1.2km. The upper zone of nickel-copper mineralisation intersected in YARC0022 appears to be relatively localised, as predicted by airborne electromagnetics, but may yet also prove to be significant.
A further 5 RC holes have been drilled at the Northwest soil anomaly, a large PGE-Ni-Cu anomaly approximately 1,000m west of Serradella, intersecting thick sequences of pyroxenite, metagabbro and metasediments, with minor disseminated sulphides. The geology of the area is not well understood but does appear to be part of the main Yarabrook Intrusion. The source of the PGE-Ni-Cu soil anomaly cannot be determined until assay results are returned.
Serradella is now considered a unique part of the Yarabrook Intrusion. The northern part of the Yarabrook Intrusion hosts rocks that are interpreted to be much deeper in the stratigraphic sequence and therefore closer to the primary basal contact of the intrusion. Consistent with this, these rocks tend to be generally higher in MgO content than at Central Yarabrook Hill. The stratigraphically lower, more MgO-rich parts of intrusions are typically the most prospective.
The Company has long recognised the Brassica trend as a prospective belt of mafic and ultramafic rocks striking over 17km within the Company’s project area. Mineralisation potential has been demonstrated by previous drilling of anomalous nickel-copper sulphide mineralisation, providing strong evidence of orthomagmatic mineralisation in the area.
The XC-46 anomaly (and nearby XC-45 anomaly) was identified during the December 2021 AEM survey (see ASX announcement from 23 March 2022). The anomaly is a strong late-time anomaly with continuity across multiple survey lines over 200m. Ground electromagnetics confirmed two discrete conductive plates (XC-46a & XC-46b) at the anomaly.
A single hole was drilled through each plate for a total of 432.8m. The northernmost hole, YAD0024, drilled the south-eastern edge of modelled plate (XC-46b) and intersected three main zones of blebby to stringer and shear style magmatic sulphide mineralisation spanning intermittently over 48.5m from 36.9m to 85.4m downhole. Minor nickel and copper sulphides were observed amongst more abundant iron sulphides, with total sulphide content locally up to 10%.
The southernmost hole, YAD0023, was targeted at the centre of a lower conductance modelled plate (XC-46a) and intersected a single zone of sulphide mineralisation over 19.5m from 63.3-82.8m downhole. Minor nickel and copper sulphides were also observed but were generally less abundant than in YAD0024.
Visual geological logging, supported by portable XRF data, show that both sulphide content and associated Ni-Cu tenor is markedly higher in YAD0024. Pending geochemical assays and downhole electromagnetic (DHEM) surveys will help to better evaluate the significance of this mineralisation and guide further drilling at the prospect. However, as YAD0024 intersected the south-eastern edge of the plate, it is anticipated that step out drilling further to the northwest along the approximately 100m long plate could conceivably encounter stronger sulphide mineralisation coincident with the highest modelled zone of conductivity.
Previous work along the Brassica trend has focused on individual and isolated AEM anomalies (XC-05, XC-06 and XC-29) which collectively make up only a tiny fraction of the broader ~17km long Brassica Shear Zone. The Brassica Shear Zone is defined by a belt of structurally dislocated lenses of mafic-ultramafic intrusive rock that is likely the extension of the Julimar intrusive complex to the south, with mineralisation potentially remobilised along this shear zone. The Brassica Shear Zone shows considerable similarities to Yarabrook Hill and XC-22 across various datasets, most notably:
- Broad and locally complexly deformed strong magnetic anomalies mapping the likely location of ultramafic serpentinised peridotites
- Variably associated gravity anomalies demonstrating large accumulations of dense mafic-ultramafic rocks
- Multiple shallow and poorly constrained AEM conductivity anomalies
- Numerous surface Ni-Cu-PGE anomalies in soil data within the area, with large strike lengths yet to be sampled
There remains potential for separate or isolated intrusions elsewhere within the shear zone or the broader project area, with the Yenart magnetic anomaly a likely example of a discrete magmatic intrusion.
Given the encouragement to date from relatively sparse exploration along a prospective belt of rocks that hosts a new world-class PGE-Ni-Cu deposit only 40km to the south, the Brassica trend is an important discovery opportunity that warrants further exploration and which the Company is keen to progress alongside its other priorities.
For further information on the Yarawindah Brook Project please view our latest ASX Announcements.