The Imbin Project (Lodestar 100%)

Targeting VMS copper in under explored interpreted rifted margin – significant historic copper and gold anomalies extend over 20km The Imbin project is located 180 kilometres northeast of Wiluna. Age dating of the Proterozoic sediments in this eastern extension of the Capricorn Orogen gives ages similar to those expected for the Bryah Basin, implying that the sequence was deposited at a similar time to the Bryah Basin and may have potential to host high value VMS style mineralisation. This interpretation is reinforced by the extensive Cu-Au anomalies in historic exploration. The Bryah Basin is an important host for significant copper and gold deposits, including the DeGrussa discovery of Sandfire Resources NL and Horseshoe Lights. Equivalent age rocks in volcanosedimentary basins along the northern margin of the Yilgarn Craton may have similar prospectivity and therefore historic gold and copper prospects in the Imbin region have added significance when considered in the context of the tectonic setting, gold and copper endowment and the Cu-Au metal associations of the Bryah Basin. Four applications and one granted tenement cover over 50 kilometres (900 square kilometres in area) of strike over a sequence of weakly to strongly deformed sedimentary rocks with intercalated Bryah-age felsic rocks and mafic intrusives (a prospective siliciclastic-mafic sequence, host to Besshi-style VMS deposits). A 20km long gravity anomaly within the belt may be attributed to ultramafic to mafic rocks associated with volcanic activity related to rifting. The concept of an adjacent rift axis is supported by the presence of previously unrecognised, dense ultramafic rocks within the regional gravity anomaly. Other potential styles of mineralisation within the belt include SEDEX copper and orogenic gold. Historic exploration has outlined gold, copper arsenic, lead and antimony anomalies extending over 20km of strike. Drilling targeted anomalies related to outcropping gossans or ironstones in four areas and significant Cu mineralisation was discovered at the Main Gossan prospect where drilling has reported intersections within graphitic shale, including;
  • 36m at 0.76% Cu, 0.11g/t Au and 2.91g/t Au in RC drilling including
    • 2.0m at 4.65% Cu and 17.5g/t Ag
  • 1.5m at 2.98% Cu and 0.12g/t Au within a 15.8m intersection of semi-massive to massive sulphide in a diamond drill hole. The intersection reported very poor core recovery and was not effectively sampled.
  • Elsewhere, limited drilling has reported up to 23m at 0.3g/t Au and 16m at 0.18% Cu at the Catalina prospect.
The sequence consists of folded sandstone, mudstone, siltstone, carbonaceous shale, chert intruded by conformable dolerite sills.  The relationship between the sedimentary and intrusive rocks and alteration and mineralisation is not well understood. Bunting (1986)[1] compares the sequence to the Karalundi Formation in the Bryah Basin and interprets the depositional environment as an active and rapidly sinking basin margin transitional into a deeper trough – the geological features are consistent with a rifted basin margin. The key features of the Imbin project are
  • Geological associations consistent with a rifted basin margin setting, age equivalent to the Bryah Basin and prospective for VMS style mineralisation,.
  • Evidence of significant copper mineralisation in bedrock drilling and extensive copper-gold anomalies that require follow up drilling.
  • Historic exploration focussed on areas of outcropping ironstones or gossans, large areas under shallow aeolian sand cover were inaccessible to surface geochemistry and have not been effectively explored.
[1] Bunting, J. A., 1986. Geology of the Eastern Part of the Nabberu Basin Western Australia, Bull. 131 Geol. Surv. Western Australia p12.

Imbin project copper in drilling (background 1VD magnetic image).

Imbin project gold in drilling

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