Porphyry Exploration & Development
Dart Mining’s key founding strategy was to seek opportunities for porphyry-style mineralisation in NE Victoria. NE Victoria has a variety of prospective granitic plutons, which have been demonstrated by Dart Mining and others to contain Cu, Au, Ag, Zn, Li, Sn, Ta, Mo and W. Dart Mining recognised the unique tectonic setting of the region, located above a large strike swing in the Gilmore Suture and straddling an Arc – Back Arc setting, imparting juxtaposed metallogenic signatures and mineralisation styles of both settings – the Unicorn Cu-Mo-Ag Porphyry deposit being a recent porphyry discovery by Dart Mining (see Map below). The region is thought to be underlain by the Macquarie Arc, the host rocks of porphyry gold, gold/copper and copper porphyry mineralisation further north into NSW at mining centres around Cadia – Ridgeway and the Endeavour deposits. This is a highly prospective area and is recognised by the Geological Survey of Victoria as being one of two newly recognised Arc Belts within Victoria, the other being the Stavely Belt in western Victoria.
Dart Mining has already made significant discoveries in altered, oxidised, fractionated, I-type intrusions at Unicorn and Morgan (see Map below) with previous explorers discovering polymetallic mineralisation, including gold and silver at the Mammoth Porphyry some 70km south of Corryong.
Dart Mining’s recent exploration history has focussed on zones of alteration within demagnetised oxidised plutons. This resulted in the discovery of strong geochemical anomalies over demagnetised zones at Gentle Annie and Staceys (both within EL4726) that await drilling. Historic Mining at Granite Flat (EL006277) focussed on high-grade gold concentrated in shear zones within the Banimboola pluton. However, Potter (1997) identified two mineralising phases, a broad low grade signature (potential porphyry style stockwork Au / Cu) overprinted by narrow, high grade zones. Potter (1997) recognised a more mafic phase of the intrusion that is not strongly sheared and shows no obvious lode style quartz mineralisation. The potential porphyry style gold and copper mineralisation is disseminated (possibly associated with micro-breccia and 2 – 5mm quartz veining), present as free gold and chalcopyrite blebs. Chalcopyrite up to 1 – 2% in hand specimens (petrographic samples) is present as scattered clots up to 4mm in size, a 2m interval from 30 – 32m in hole DD91 BO2 shows 2.81 g/t Au, 0.88% Cu and 7 g/t Ag from this mafic phase (see EL3025_G27419_199711_Annual Report Source: http://geology.data.vic.gov.au/searchAssistant/document.php?q=reference_id:27419
A Porphyry Exploration Strategy will comprise the de-risking of known and potential porphyry mineralisation via targeted drilling and alteration studies, all work being focussed toward farm-out arrangements with majors or joint venture partners to take projects through to production with a retained interest.
Given the potential scale of the porphyry projects and the attractiveness of that scale to majors, whose production profiles are continuously eroding, Dart is confident of finding partners to help uncover this potentially extraordinary value.
The challenge for Dart is to get the balance right between further internally funded exploration and externally funded JV exploration. Carried interest percentage is the key in this equation for the creation of shareholder value.