Manbarrum Zn-Pb-Ag Project, Burt Range Shelf, Bonaparte Basin, NT: Conference Abstract

Abstract

In its first six months of operation in the Bonaparte Basin of north-western Australia, Tennant Creek Gold Ltd (TNG) has significantly advancement the resource potential of the Manbarrum Zn-Pb-Ag Project. TNG successfully completed 62 Reverse Circulation (RC) drill holes for 9,471m on a 50 by 50m grid. Contemporaneously, the company conducted an IP survey which covered selected parts of the tenement holding in the area. Individual ground-gravity traverses were also carried out. The Sandy Creek Prospect was discovered by Aquitaine Australia in the mid-1970's. The prospect area was explored by several companies until the late 1990's. A pre-JORC resource of 3.2Mt @ 4.5%Pb, 2.4%Zn and 15g/t Ag was delineated at the prospect in the early 1980's by Aquitaine and its partners. The Sandy Creek Prospect was believed to contain primarily structurally-controlled lead mineralisation. The Sandy Creek Prospect is located in the Burt Range sub-basin of the southern onshore Bonaparte Basin. The mineralisation is hosted in Lower Carboniferous shallow-marine clastic (sandy) dolomite rocks of the Burt Range Formation which unconformably rest on Proterozoic basement and in turn are unconformably overlain by fine-grained carbonaceous siltstones and sandstones of the Upper Lower Carboniferous Milligans Formation. TNG has been able to demonstrate that the mineralisation is dominated by zinc-lead-silver sulphides replacing the carbonate matrix of the host formation in the form of disseminated and massive sulphides. The morphology of the deposit appears to be controlled by sub-vertical, possibly deformation-induced porosity and by stratigraphic controls, particularly the carbonate-shale contact which forms the hanging wall to mineralisation. The location of mineralisation at Sandy Creek corresponds closely with a surface (soil) geochemical anomaly and the location of a west-dipping IP (chargeability) anomaly. Regional and prospect-scale gravity data do not provide sufficient detail over the prospect area, however, the data suggest that the mineralisation is situated near the margin of a gravity high (slope). The major advancements to the project were made by TNG in the areas of geological understanding, mineralisation geometry, mineralisation, and geophysical controls and can be summarised as follows: - Zinc is the primary economic commodity at the Sandy Creek Prospect with lead occurring on average at a ratio of 20:1. Lead is estimated to constitute about 20% of the deposit (preliminary visual estimates). Base metal intercepts of combined zinc and lead greater than 2 to 3%, show silver values generally exceeding 20g/t. - The deposit includes a supergene and a primary mineralisation zone with the primary (hypogene) zone dominating the overall mineralisation volume. - The centre of mineralisation is a sub-vertical pipe-like body with a flat and shallow-dipping top. - A strong correlation exists between an IP (chargeability) anomaly and the main zinc mineralisation. - The bulk of the mineralisation is interpreted to be represented by a matrix-replacement style of mineralisation. - The insight TNG has gained from the discovery of this deposit will be used to effectively guide future exploration.