Summary:
Caravel Copper Project combines Bindi, Dasher, and Opie deposits.
Mineralisation at the Caravel Copper Project is hosted by a highly deformed Archaean granite and considered to originate as a large porphyry copper system.
The mineralised granitic gneiss at Bindi has been deformed into a tight fold, overturned to the east with the fold hinge plunging to the northwest.
The mineralization typically forms broad, tabular zones in the order of 50-100m true thickness, zones of higher grade material are associated with fold hinges.
The mineralisation at Bindi typically consists of chalcopyrite + molybdenite, stringers and disseminations with associated pyrite ±pyrrhotite ±magnetite within a coarse-grained, quartz-feldspar-biotite ±garnet ±sillimanite gneiss.
The mineralised granitic gneiss at Bindi is overlain by upto 40m of largely barren regolith consisting of an upper laterite and saprolitic clay. Minor oxide (supergene) mineralisation is variably developed as a sub-horizontal zone within the regolith profile east of the Bindi East Limb and at the southern end of the Bindi West Limb.
The mineralisation at Dasher is very similar to Bindi except the mineralised gneiss occurs in a moderate east dipping window between younger granites and the regolith profile is much thinner.
The granite host rock, the inferred pre-metamorphic mineral assemblages and general scale and style are all consistent with the porphyry copper model. The broader geological setting is also consistent with a porphyry style of mineralisation, with the 30km mineralised trend following the margins of granite batholith of similar scale, referred to as the Wongan Batholith.
Outhwaite (2017) describes in detail age dating work and the tectonic history of the project area. Host granites and associated mineralisation have been dated at around 3.0 Ga, with subsequent deformation and metamorphism around 2.7 Ga, coincident with the regional deformation and gold mineralisation at Kalgoorlie and the wider Yilgarn goldfields, as well as the Boddington gold deposit.
Copper occurs almost exclusively as chalcopyrite sulphides associated with quartz veins. Copper grade is largely determined by the frequency and thickness of the veins, which may be semi-massive chalcopyrite up to several cm thick, though mostly the sulphide veins are more attenuated and in the range of mm thick following the main foliation. The frequency of veins or sulphide bands also varies on the scale of meters and tens of meters, where copper grades may range up to 0.6% over thicknesses of tens of meters with lower grades or waste in between.
Molybdenite, pyrite and pyrrhotite may accompany the chalcopyrite, though in much lower levels. Garnet, sillimanite and magnetite are also commonly associated with mineralisation, possibly as products from metamorphism of the primary alteration assemblages. Garnets have an almandine composition and are coarse grained, often overprinting the foliation. Both garnet and magnetite occur in sufficient abundance that they may offer opportunities as by product minerals to be recovered from the tails stream with economics still to be evaluated.
The mineralised zones have undergone higher strain than adjacent barren granites in the footwall. In the higher strain zones, the mineralised veins have been transposed into the dominant foliation.
Detailed geotechnical and structural logging from drill core has identified these foliation trends form well defined groupings that are consistent with the interpretation that the Bindi West and Bindi East Limbs converge to form a NNW plunging fold structure, the closure of this fold is termed the Bindi Hinge Zone. At the southern end of the East Limb there is evidence for another fold termed the SE Synform, where the East Limb remains open to the east and may return to surface in an area recently shown to contain significant bedrock copper mineralisation immediately east of the planned Bindi pit. The fold closures are often associated with better grades of mineralisation, possibly due to remobilisation of sulphides into the fold hinges, so the identification of these structural models has been important in both the targeting of better grade areas and the development of the Resource models.
Dimensions
Bindi West Limb of 2,950m along strike (NNE-SSW), ranging between 50-200m thick and present from surface (260mRL) down below -150mRL.
Bindi East Limb of 2,000m along strike (N-S), ranging up to 500m thick from surface (260mRL) down below -500mRL.
Dasher mineralized zone of 2,600m along strike (N-S), ranging up to 250m thick from surface (320mRL) down to -200mRL.