Stavely Minerals (ASX:SVY) reports it is preparing to begin a new phase of exploration activity, targeting rare earth elements (REEs) at its 100% owned Stavely Copper-Gold Project, located in western Victoria.
During the 2021-22 field season, Stavely conducted a regional exploration program including 400m by 400m spaced soil auger sampling in areas of sub-crop while areas with younger basalt cover and transported Tertiary cover were tested by vertical (AC) drill holes.
A total of 12 of 19 identified ‘blind’ prospects were tested.
Additionally, the more advanced Toora West target was tested with four diamond drillholes and was confirmed to host porphyry-style mineralisation, albeit with apparently only a single pulse of porphyry mineralisation which is considered insufficient to produce an economic deposit.
The Toora West prospect is ‘blind’, being located beneath 30m of yonder transported cover, and demonstrates that Stavely Minerals’ targeting process has successfully identified mineralised systems under cover.
A total of 106 soil auger samples were collected to the north and south of the Lexington Prospect over the Buckeran Diorite Intrusion, Yarrack Fault and surrounding volcano-sedimentary rocks,
The Lexington Prospect area was not sampled due to land access issues.
The auger sampling was designed to test for anomalism associated with porphyry-style mineralisation as observed at the Cayley Lode at the Thursday’s Gossan Prospect, located on the adjacent tenement RL2017.
Sampling has identified weak As and Bi anomalism on the south-west margin of the intrusive complex.
Additionally, samples SSL13042 returned Ce (over 500ppm) at above the detection limit, and was re-assayed for an additional suite of rare earth elements (ALS method ME-MS81).
A Ce value of 886ppm was returned for this sample. Oxide conversion of the REE results returned 0.24% TREO+Y.
Of note, the results indicate that a significant portion of the contained REE in Sample SSL13042 are the ‘high-value’ REE magnet metals Neodymium (Nd) and Praseodymium (Pr). The adjacent sample, SSL13033 also returned an elevated Ce value of 286ppm.
The minerals bastnasite and monazite are common in carbonatite composition intrusions, which generally occur in larger intrusions of alkali-rich silicate igneous rocks.
The minerals bastnasite and monazite are common in carbonatite composition intrusions, which generally occur in larger intrusions of alkali-rich silicate igneous rocks
Carbonatites weather recessively which might account for the lack of outcrop in the southern lobe of the Buckeran Diorite.
From the data available, there appears to be potential for a REE-enriched carbonatite or perkalkaline intrusion in the Narrapumelap Prospect area.
This will need to be confirmed with additional soil auger sampling and aircore (AC) drilling prior to any definitive diamond drilling.
Stavely Minerals Executive Chair and Managing Director Chris Cairns said the company is very excited to be approaching its new exploration field season in Western Victoria.
“Stavely Minerals has evolved with a diverse suite of targets ranging from those slated for initial testing to targets which require follow-up based on previous anomalous results.
“The new Narrapumelap REE target was unexpected and is at a very early stage of evaluation, but has the potential to evolve into something completely different to our previous and ongoing copper-gold focus.”.
Proposed follow-up work programs include in-fill soil auger sampling from 400m by 400m in the initial program to 100m by 100m in the immediate vicinity of soil sample SSL13042 and broader 200m by 200m in-fill sampling in other areas of REE anomalism.
These in-fill soil auger programs will commence once ground conditions allow tractor with auger access.
Victoria, along with most of southeast Australia, has experienced a third consecutive La Nina weather event with an extremely wet winter and a wet spring forecast.
Stavely Minerals has no view on whether the soil auger samples may demonstrate enrichment or depletion of REEs through surficial/regolith weathering processes.
Once coherent REE soil auger anomalies are defined, a program of AC drilling to acquire fresh bedrock samples will follow and provide a better indication with respect to bedrock REE abundances, and this would be followed by definitive diamond core drilling if warranted.
Investors are cautioned that while the Narrapumelap REE prospect is an exciting emerging opportunity, it is at the very earliest stage of evaluation.
Stavely applies a model for interpreting the alteration, sulphides noted and geochemical signatures within a framework developed by the Mineral Deposit Research Unit at the University of British Columbia for the multi-element geochemical zonations above and proximal to porphyry copper-gold deposits.
This guide allows interpretation of alteration noted in AC drill chips and geochemical pathfinder elements to determine where in the vertical column of a hydrothermal porphyry system the results are reflected.
‘High-level’ alteration and geochemical signatures may be prospective for structurally-controlled ‘high-sulphidation’ or lode style copper-gold, but may also be too far vertically above porphyry-style mineralisation.
Likewise, strong molybdenum and copper geochemistry, in conjunction with inner-propylitic or outer potassic alteration, would demonstrate the potential for proximal porphyry copper-gold style mineralisation.
During the 2021-22 field season, a total of 12 of 19 previously identified targets were tested with AC drilling.
The 19 regional targets were identified by interpretation of regional aeromagnetic gravity gradiometer and historic exploration data.
The majority of these regional targets are ‘blind’, covered by either younger basalt flows or younger transported cover, or in some instances both.
Of the targets tested with AC drilling, some 80% of targets demonstrated hydrothermal alteration ± sulphides ± quartz veining.
Stavely is ‘very encouraged’ by the effectiveness of the targeting criteria, with significant results returned from a number of targets that require follow-up work.
The Toora Road target is within recently granted EL7347, and aircore results from previous explorers include 15m @ 1.28g/t Au, 11g/t Ag, 0.26% Cu, 0.94% Pb and 0.1% Zn from 12m drill depth to end of drillhole WL030.
The results from hole WL030 can be interpreted in the context of experience at the Cayley Lode as a distal base-metal and precious metal intercept.
The anomaly is located on a magnetic high along a trend of highs that extend north-west from the Cayley Lode and the Northern Flexture Prospect.
The magnetic highs at the Cayley Lode and the Northern Flexture Prospect are caused by serpentinised ultramafic with abundant magnetite.
Additionally, the Toora Road drill intercept is located to the north of a distinct circular gravity low that may reflect a buried intrusion/intense hydrothermal alteration.
Located 1.5km north of Thursday’s Gossan, the Northern Flexture target occurs along the margin of the structurally offset slice of the Williamson Road Serpentinite, in a similar dilatant structural position to that of the Cayley Lode.
Anomalous zinc, silver, manganese, molybdenum and copper results were returned from soil auger sampling during the 2021 field season.
Work plan submission and follow-up soil auger, AC and potential diamond drilling is planned to test this anomaly in the upcoming field program.
Junction 1 forms the largest (1,200m by 500m) and highest tenor soil auger copper anomaly identified in the Stavely Project area.
The majority of the soil auger and rotary air blast (RAB) drilling on this target was completed in the 1980s.
The anomaly is located 3.5km south-southeast of the Cayley Lode along a sub-cropping portion of the Stavely Volcanic Belt.
Limited AC and diamond drilling intersected a best result of 35m @ 3.4% copper from 24m drill depth to end of hole in TGAC078.
Shallow RAB conducted in the 1980s throughout most of the anomalous zone may have not penetrated past the leached zone, as has been seen in Thursday’s Gossan.
Once access agreements are in place, in-fill auger sampling using modern analytical techniques will be completed and angled AC holes designed in search of the source of this significant copper anomaly.
Previous drilling by the company to follow up on TGAC078 intercept resulted in intersections of peripheral base-metal mineralisation (e.g 5m @ 0.37% Pb and 2.4g/t Ag in SMD077 from 275m drill depth) and will require a full review of structural orientations at Junction 1 once the proposed soil auger and AC programs are complete.
The S41 target area comprises an aeromagnetic low with coincident gravity low.
This anomaly was selectively tested by North Limited AC drillholes.
However, these holes failed to test basement, having intersected clays and intervals of tertiary basalt from surface.
At the S41 target, Stavely Minerals drilled 8 AC holes along two lines 1.5km apart, with holes spaced 400m apart for a total of 749m.
AC drilling by Stavely successfully penetrated these cover rocks and intersected strongly silica sericite altered dacite porphyry with weak disseminated pyrite.
This style of alteration with associated sulphides and geophysical characteristics justifies priority AC follow-up.
At the S41 Prospect, strongly sericite+quartz+pyrite-altered dacite was observed at the base of hole STAC0071. Disseminated pyrite also occurred in STAC0009.
The Ac drilling returned assays up to 0.025g/t Au, 3.57g/t Ag, 7.37ppm Sb, 564ppm Cu, 286ppm As, 5.47ppm Mo and 0.77ppm Bi.
Overlapping zones of anomalous Cu, Mo, Au and Ag extend through the S41 and adjacent S29 target areas.
The S41 Prospect is considered a priority target for follow-up in-fill AC drilling.
Located 3.5km southeast of S41 within the Elliot volcanic segment, S29 is characterised by an aeromagnetic low with coincident gravity low.
Like S41, previous AC drilling failed to penetrate the tertiary basalt, however AC drilling completed by Stavely intersected kaolinite altered dacite porphyry with trace quartz-pyrite veining in STAC013.
At the S29 Prospect, the AC drilling returned assays up to 0.046g/t Au, 1.07g/t Ag, 359ppm Cu, 5.63ppm Mo and 1.3ppm Bi. The S29 Prospect is considered a priority target for follow-up in-fill AC drilling.
The alteration and mineralisation identified at the Nekeeya Prospect alteration lies south of the Navarre Minerals’ Morning Bill Prospect within the Glenlyle Project.
At Nekeeya, extensive AC drilling by the company transects a broad gravity high several kilometres wide which partly encloses several gravity lows.
The elevated gravity anomaly appears to correlate with andesite flows which have undergone chlorite-epidote alteration observed in AC rock chips, whereas clay altered mudstone has been noted in the gravity lows.
There is a suggestion that the structural grain, characterised by the 340º orientation of the Moyston Fault on the eastern side of Nekeeya and extending south towards the Bunninjon anomaly, might vary from 311º in the central and western portion of the Nekeeya anomaly.
Alternatively, the 311 degrees orientation may be reflecting a northwest oriented linking structure.
If this is the case, Nekeeya may exhibit a dilatant character similar to Cowal, not present at Glenlyle in the formation of the Morning Bill mineralisation.
The geophysical feature is interpreted to represent the eroded remnants of a submarine stratovolcano, situated on possible arc parallel faults that were later reactivated.
Current exploration at Nekeeya has focused upon a 1km by 2km gravity low dominated by clay altered mudstone with lesser andesite in which AC drillholes to date have identified anomalous Ag, As, Sb, Ba and Mo, including a 1.5km by 1km over 5ppm Mo anomaly.
The AC holes returned strongly anomalous assays in epithermal and porphyry pathfinder elements including up to 10.85ppm Ag, 0.06ppm Au, 3,720ppm As, 1,295ppm Cu, 35.8ppm Mo, 409ppm Zn, 266ppm Sb, 0.94ppm Bi and +10 weight % S.
The geological setting, wall rocks, hydrothermal alteration and geochemical signature are all consistent with the setting of Nekeeya being within wall rocks well above a magmatic source in the epithermal regime.
If present, a Cowal-Cayley Lode structural setting, characterised by north-west dilatant structures formed as a result of transient sinistral strike-slip movement on the north-south structural grain, might provide an environment required for the formation of epithermal transition to porphyry and possibly wall rock porphyry (Cadia East) mineralisation at Nekeeya.
Continued exploration could include in-fill AC drillholes currently at 400m centres on lines about 750m apart, while further processing of gravity and magnetic data might investigate for the presence of a north-west flexture in the structural grain that might provide encouragement to progress to a northeast-southwest oriented diamond drill test.
The Nekeeya Prospect has been rated as priority B, that is of some interest and should be subject to further work if funds are available.
The economic mineralisation may be deeply buried and ‘higher-level’ copper-gold mineralisation may be only likely to develop in the presence of favourably dilatant structural setting.
However, the strongly anomalous copper and molybdenum assay results may indicate that there may be some degree of alteration overprint on a deeper portion of the large hydrothermal system at Nekeeya.
Stavely Minerals is a mineral resource company focused on the exploration and development of the Stavely, Yarram Park and Ararat copper-gold-silver projects in western Victoria.