Introduction
The Yandicoogina Project is located 55km southeast of Marble Bar in the east Pilbara region of Western Australia and covers 99.8km² in Exploration Licence E45/2578.
Geological Setting
The Yandicoogina Project is situated within the southern part of Marble Bar greenstone belt which rims the MEGC. The MEGC consists of hornblende granodiorite and quartz monzogranite intruded by irregularly shaped bodies of quartz plagioclase porphyry. Along the southern margin, fine to coarse grained amphibolite schist and deformed dykes and pods of dolerite are common.
Figure 8 Yandicoogina Project – Mineral Occurrences & Exploration Targets
Inset: Bamboo Creek – Mineralisation & Structure in Euro Basalt Host
The greenstone belt consists of the volcanic and metavolcanic rocks of the Duffer Formation, the Apex Basalt, the Panorama Formation and the Euro Basalt which are all within the Warrawoona Group. All of these rocks outcrop prominently in the tenement area. The Duffer Formation at the contact of the MEGC strikes over some 18km.
Previous Mining and Exploration
Gold was discovered in the Yandicoogina area in the late 1890s and mining continued for about ten years. Numerous pits and shafts were developed on rich mineralised quartz veins, with historic production recorded as 3304t mined at an average grade of 60.76g/t Au. The highest grade of ore came from the Invincible Mine which yielded 13.4 tonnes of gold at 1,485 g/t.
In 1988, a five hole reverse circulation drilling program at the Eastern mine and workings targeted gold mineralisation in a quartz body associated with a shear zone within the MEBC. Split samples from three holes showed intersections of 2m @ 3.8g/t Au from 12m, 2m @ 4.0g/t Au from 18m, 2m @ 1.9g/t from 20m, and 2m @ 1.4g/t from 8m.
Little recent gold exploration has been conducted in the tenement area.
Extensive exploration for base metals has been carried out at the northeastern end of the tenement at Lennons Find (excised from the tenement). Lennons Find was discovered in 1907 and was subject to small scale mining through to 1960. In 1976-77 Serem carried out a major drilling program, establishing the presence of a stratiform volcanogenic Zn, Pb, Ag and Cu resource within the Duffer Formation.
Prospects and Mineralisation
Gold
The historic line of gold shafts and workings at Yandicoogina is indicative of the potential for mineralisation along the 18km of strike of the Duffer Formation within tenement E45/2578. At the workings mineralised quartz veins are present in the zone of intense shearing along the margin of the MEGC, the veining occurring in felsic schist (metamorphosed sedimentary and felsic volcanic units of the Duffer Formation) and in sheared granitoid.
Potential mineralisation targets within the Warrawoona Group are further indicated by the proximal gold mining at Bamboo Creek, 50km to the north and at Marble Bar 50km to the northwest.
The Bamboo Creek mining centre has produced approximately 800,000t of ore @ an average 8.15g/t Au, the majority of production occurring since 1986.The main control for mineralisation is the bedding-parallel Bamboo Creek Shear Zone that contains serpentine-rich and talc-rich ultramafic rocks within the Euro Basalt. Within the southern part of E45/2578 the Euro Basalt is prominent and similar mineralisation settings may be present, associated with doming related fault systems occurring in this area.
The Marble Bar mining centre produced some 43,000oz of gold form the late 1900s to 1950. The ores are mainly hosted by the Duffer Formation with mineralised zones consisting of auriferous quartz veins within and marginal to sills of metadolerite. Again the potential of competency contrast of the rocks, in this case of the Duffer Formation, associated with doming related faulting and shearing proximal to the MEGC indicates a likely model for mineralisation in the similar setting present in E45/2578.
Base Metals
Base metals mineralisation potential within E45/2578 is exemplified by the Lennons Find resource (excised at the northeasten end of the tenement), and the proximal occurrences at Big Stubby, which lies outside of the tenement 6km south of Marble Bar. The Duffer Formation, which extends over 18km of strike in E45/2578, is a recognised host for base metals mineralisation for these deposits.
The mineralisation style, combined with its features of vertical metal zoning, texture and stratiform mode suggests that the deposits are of volcanogenic origin (volcanogenic massive sulphide, VMS).
Gossans 6km south of Marble Bar, and, 40km northwest of the tenement, mark the Big Stubbydeposit which is made up of seven massive subvertical lenses of Zn-Pb-Cu-Ba mineralisation within felsic to intermediate volcanic and volcanoclastic rocks near the top of the Duffer Formation.
Discussion
Potential for Gold
Very substantial strike lengths of Duffer Formation and Euro Basalt occur within the Marble Bar greenstone belt in E45/2578. Gold mineralisation at Yandicoogina, within the tenement, and gold mineralisation settings at the proximal Bamboo Creek and Marble Bar mining centres, indicate that good potential exists for a range of mineralisation settings within the tenement. These are as follows:
- Mineralised quartz veining along the sheared margin of the MEGC within the Duffer Formation and the granitoid itself. This applies to the area of the Yandicoogina mining centre and the entire strike length of the Duffer Formation in E45/2578.
- Mineralisation associated with competency contrast of felsic rocks and mafic and ultramafic rocks of the Duffer Formation and associated doming related fault and shear systems further away from the MEGC-Duffer Formation contact.
- Mineralisation associated with competency contrast of the mafic, ultramafic and sedimentary units of the Euro Basalt controlled by fault and shear systems associated with doming.
In general terms the east Pilbara region is only now receiving a renewed modern exploration initiative and from this impetus new discoveries are likely.
Potential for Base Metals
Previous exploration for base metals on tenement E45/2578 has been limited to the excised area at the northeastern end of the tenement at Lennons Find, where a significant deposit has been recognised.
Potential for VMS and stratabound volcanic and sedimentary mineralisation is recognised within the Duffer Formation in E45/2578 along its 18km strike length present in the tenement.
