Exploration of the Teena Zinc Prospect New insights for the discovery of shale-hosted zinc deposits in Northern Australia

Teena is the most significant zinc discovery for 25 years in the world-class Carpentaria Zinc province of northeast Australia. It is located just 8 km west of Glencore’s McArthur River Zn-Pb Mine (190 Mt at 9.8% Zn, 4.3% Pb and 44 g/t Ag (Glencore 2015). Teena lies within the same stratigraphic host unit, but in a separate 4th-order sub-basin along a different structural corridor. The discovery was made by Teck in partnership with Rox Resources in 2013 whilst testing a new high-grade target in the Teena Sub-basin. High-grade stratiform mineralisation has now been intersected over a 1.5 km strike extent, at depths of 600 –1000 m, with several intercepts of >10 m thickness at 13% to 17% Zn+Pb; this includes a peak intercept of 38.8 m at 16.9% Zn+Pb (Rox Resources Ltd 2015). The sub-basin depocenter formed as an asymmetric halfgraben with up to 800 m normal throw in an extensional fault relay along the south-dipping Jabiru-Bald Hills Fault Zone. We attribute formation of mineralisation at ca 1640 Ma to be related to NNW–SSE extension, not WNW – ESE compression or extension, as previously proposed (McGoldrick et al 2010). Despite its Paleoproterozoic age, inversion effects are minimal. This insight has important implications for target prediction. Mineralisation is hosted by the reduced Barney Creek Formation (BCF), the transgressive facies between the Reward and Teena dolostones. The BCF transitions from basal, thinly interbedded, dolomitic-siliciclastic sandstone– siltstone beds to laminated carbonaceous and pyritic siltstone–shale beds. Importantly, stratiform mineralisation occurs in the lower dolomitic carbonaceous shale facies, significantly below the maximum flooding surface. It comprises two lenses separated by the thickest sandstone mass flow units present in the basin, reflecting maximum fault subsidence. In contrast to the McArthur River deposit, dolomite talus breccias are very restricted to the immediate Jabiru Fault hanging wall. Two main stages of mineralisation comprise: (a) early diagenetic, fine-grained, laminated sphalerite with Exploration of the Teena Zinc Prospect – New insights for the discovery of shale-hosted zinc deposits in Northern Australia