|
Deposit Synonyms
Challenger I; Challenger West; Ml 6103; Ml 6457
Mineral District
Deposit Summary
Au-As-Bi mineralisation in 3 main NE-trending shoots in host Archean migmatitic, qz-fx-gn gneiss, plunge 30 to 030, mineralisation remaining open at depth. Resources 1,852,213t @ 8.45g/t Au (2006). Production 2002-09 ~17.6t gold bullion.
Deposit Description
CHALLENGER, gold deposit discovered in 1995 by a Dominion-Resolute JV during follow up drilling of a gold-in-calcrete anomaly. Gold mineralisation occurs in a host synorogenic, high-grade, granulite facies metamorphic terrain (~2.41-2.46 Ga) of the Christie Gneiss (~2.9Ga), overlain by retrograde amphibolite facies recrystallisation (1650-1450Ma).
High-grade gold mineralisation is developed within a number of NE-trending lodes in host migmatitic, quartz-feldspar-garnet-biotite-cordierite gneiss of Archean age interpreted as volcaniclastics that underwent pre- to early-metamorphic epithermal style mineralisation. The Challenger structure has been defined as a laterally extensive shear zone with ore shoots plunging 30 to 029.
The ore shoots are defined by leucosome veins, which are characteristically ptygmatically folded, with the small-scale folds parasitic to overall larger scale folds. The folding has been interpreted as synchronous with peak metamorphism along with gold mineralisation. Gold mineralisation was emplaced as partial melts into low-strain positions. McFarline et al (2007), using monazite geochronology proposed a 40Ma mineralisation period from 2460-2420Ma during repeated hight T episodes. Post-folding, the ore shoots were subjected to extreme WNW-ESE shortening and extension directed shallowly to the NE. There are cross cutting dykes of lamprophyre (1950Ma), diabase, and K-feldspar pegmatite.
Overall form of Challenger deposit is pipe-like, comprising a number of shoots, including several high-grade shoots. Drilling to mid 2017 has confirmed Main Shoot (M1) with a down-plunge extension from surface (1193mRL) to ~2800m, with several adjacent shoots also remaining open at depth. At Mine Grid level RL 215m (AHD 1215m), shoots are displaced sinistrally by ~220m in a cross fault (age ~1405Ma). Proven surface strike length is ~750m, width ~250m.
Individual shoots have variable stylised spatial forms related to their structural style. The structural styles include folded migmatite packages occurring as a series of ‘short-limb’ fold packages, with m-scale folded veins (M1), connected by ‘long-limb’ more highly strained packages (M2). Also linear, shear-hosted lodes (M3, Challenger West).Host migmatite has frequent in-situ pegmatitic intervals. 3 main types of leucosome/vein styles have been recognised, quartz-dominant veins, possibly representing pre-metamorphic mineralised veins, polysilicate veins dominant in the main ore zones, and the main host to mineralisation, and cross-cutting pegmatitic veins, which are unmineralised, and late stage.
High grades of gold occur in coarse grained quartz veins with feldspar, cordierite, and sulphides dominated by arsenopyrite, pyrrhotite, and lesser telluride. Gold occurs predominantly (70%), as free gold, with non-visible gold dispersed in loellingite and forming microscopic inclusions in arsenopyrite, pyrrhotite, bismuth, and at quartz and silicate grain boundaries and in micro fractures. Sulphides are sparsely scattered in bluish quartz that substituted for the quartzo-feldspathic neosome in migmatite and graded into it. Geochemical associations in ore are Au-As-Bi (Ag-Co-Ni-Cu-Te). Silver content is <2%.
Initial total indicated and inferred resources published in 2006 were 1,852,213 tonne @ 8.45 g/tAu for 503,362oz (15,657kg) gold. Remaining JORC compliant gold endowment at Challenger as announced by WPG Resources in March 2017 is 343,299oz (10,679 kg), with ongoing exploration of deeper levels, and adjacent lodes indicated potential for significant additional resources. Production from 2002- June 2017 estimated at 1,134,555 oz bullion gold (excludes 2,643 oz from Tarcoola Perseverance). Historical production has been from Main or M1, M2, and M3 shoots, more lately Challenger West, with other production from lodes Aminus, M1 Shadow, Hanging Wall, and SEZ. Ore tonnage throughput had increased to ~700,000 tpa by 2017. Processing plant is conventional carbon-in-pulp
Discovery Year
? 1995
Commodities
Gold, Silver
Ore Minerals
Bismuth, Bismuthinite, Chalcopyrite, Gold
Gangue Minerals
Arsenopyrite, Biotite, Cordierite, Garnet, Graphite, Loellingite, Orthopyroxene, Pentlandite, Perthite, Plagioclase, Pyrite, Pyrrhotite, Quartz, Sphalerite, Spinel
|