Estrella Resources Limited (ASX: ESR) is continuing to expand its exploration activities at its nickel sulphide projects in Western Australia.
The company has been methodically drilling various targets within the 100% owned Carr Boyd nickel and copper sulphide project 80km northeast of the City of Kalgoorlie-Boulder and will shortly commence drilling activities at its 100% owned Spargoville Nickel Rights Project 25km West of Kambalda.
Broonhill Prospect
RC results from the Phase 4 RC Programme are currently being received and collated as the back-log at the lab is cleared. The results confirm the fertility of the T5 pyroxenite beyond the initial T5 discovery.
The Broonhill sulphide discovery lies some 1.4km to the north of T5. Several RC holes intersected sulphides in an area where the intrusion takes a more easterly turn.
The sulphides form part of the sulphide rich halo that occurs from assimilation of country rock into the intrusion, a necessary step in nickel deposit formation. Structural and stratigraphic complexity within the Broonhill rocks was noted in the RC drilling and diamond drilling is underway to understand the nature of the intrusion at this location.
A moderately conductive DHEM plate was obtained from CBP076. However, its relationship to the intrusion or country rock is unknown until drilled. The plate does appear to correspond to the Broonhill basal contact.
The type of pyroxenite intersected within the RC programme suggests fertility stops 700m north-east of Broonhill where the T5 pyroxenite ends and an overlying, barren pyroxenite takes its place on the edge of the Carr Boyd Intrusion. Further east the complex is intruded by granite.
As Phase 5 continues, a series of DHEM platform holes will be drilled to provide EM coverage over the extent of the T5-Broonhill fertile pyroxenite contact in a bid to locate further massive sulphides between Broonhill and T5.
T5 Prospect
Phase 4 drilling at T5 involved both a north and south step-out section targeting around 600m below surface as well as RC drilling above the mineralisation and to the west of Flat Fault, which dislocates mineralisation. The geology and DHEM results from the northern step-out hole with two wedges (CBDD062 and 062A) indicating that potential lay to the south of the hole, confirming the southern plunge of the T5 high-grade nickel sulphide.
The best intersection was from CBDD062A which encountered 19.8m of silver enriched, low grade nickel and copper mineralisation, containing a high-grade interval of 0.9m @ 1.31% Ni & 1.16% Cu, 6.07 g/t Ag and 0.73 g/t 3PGE (Pt + Pd + Au).
Assays are presented in Table 3. Two holes, CBDD060 and CBDD067 were targeting below the known T5 mineralisation to build a better understanding of DHEM responses at depth below a second, smaller off-set flat fault encountered in previous drilling.
CBDD060 intersected 0.75m @ 1.34% Ni and 0.72% Cu on the basal contact indicating once again the plunge of mineralisation is to the south. DHEM on this hole generated a conductive plate above the hole and just below the lower Flat Fault.
CBDD067 targeted T5 at depth to assess the lower contact with DHEM. This hole intersected 17.5m of blebby and disseminated mineralisation, indicating an increase in strength of mineralisation to the south. DHEM results from this hole are expected within one week.
A second diamond drill is imminently due on site to continue expanding the T5 mineralisation with further southern step-out holes, aimed at finding the extent of influence of the Proterozoic Dyke on the T5 mineralisation, ahead of resource infill drilling.
Mossgiel Prospect
The Mossgiel Prospect is centred about 3.5km southwest of the Carr Boyd mine site. The geology consists of a basal pyroxenite (hosting nickel-copper mineralisation) overlain by a magma-tube core of peridotites.
The Mossgiel Prospect has not received any historical drilling into the 2.5km long basal contact and the Company has identified this area as being prospective due to its location at the very base of the Carr Boyd Intrusive Complex.
Five diamond drillholes have been targeted into the Mossgiel basal contact to assess the fertility of the pyroxenites in this area and to locate the contact at depth. The contact appears to dip moderately to the east and the lower pyroxenite does contain nickel-copper sulphide accumulations.
CBDD058, CBDD059, CBDD061, CBDD063 and CBDD068 have all intersected the lower pyroxenite sequence. All holes encountered dolerite dykes in the vicinity of the contact, but also intersected varying degrees of cloud sulphides, confirming the fertility of the Mossgiel Prospect. DHEM results from these holes are expected within one week.Samples have been sent to the lab and assays are expected within a few weeks. Further holes are planned to extend DHEM coverage across the strike of the Mossgiel embayment in order to locate sulphide accumulations on the basal contact.
Gossan Hill Prospect
The Gossan Hill Prospect is the southern-most basal contact of the oldest part of the Carr Boyd Igneous Complex. Recognising this position as significant, Estrella designed an RC program to locate and define the orientation of the contact ahead of diamond drilling and DHEM.
The contact is reminiscent of that seen at T5-Broonhill. The first two RC holes at the Gossan Hill Prospect intersected zones of cloud and disseminated nickel-copper sulphides within the lower pyroxenite unit. This demonstrates the Gossan Hill Pyroxenite has had exposure to wall rock contamination and sulphide assimilation, a necessary criterion required to form nickel-copper deposits. The Company is not expecting the intersection to grade as significantly as massive sulphides due to the early stage of exploration at Gossan Hill.
However, proving the existence of a similar sulphide plume halo to that seen at T5 bodes well for future follow-up. It was not appropriate for the RC rig to continue drilling at Gossan Hill due to issues with the compressed air supply and the increase in groundwater interaction with the sample.
The RC rig was let go, to be swapped with the second diamond drill. Up until now, the 3.6km long basal contact had not received any historical drilling and remains open in all directions. Drilling and DHEM testing of this contact at depth will commence within weeks once results of the recent seismic programme have been received and the basal contact remodelled.
Stage Two Seismic Programme
The company continued its R&D partnership with Ultramag into a stage 2 seismic survey at Carr Boyd. Recommendations from the stage 1 trials were implemented and the seismic program was conducted at the end of April. Approximately 27 lineal kilometres were surveyed using the Syncro E-vibe system.
The enhancements made will enable the company to image the Mossgiel and Gossan Hill basal contacts at depth, prior to drilling. Historically, several holes drilled by other explorers at Carr Boyd have failed to find their targets at depth due to a lack of information to inform targeting. As a result, drillholes have been pushed to great lengths at considerable cost to the program, several of which still did not intersect the intended geology.
The use of seismic will be crucial in assisting the Company to better target drillholes at depth at Carr Boyd, particularly into locations such as Mossgiel and Gossan Hill, where no previous drilling has intersected the basal contact at depth.
