The granted tenements cover 23 kilometres of strike length of the carboniferous Upper Burt Range Formation dolomites within the eastern Bonaparte Basin where numerous occurrences of base metal mineralisation have been identified from previous exploration and form a classic Missippi Valley Type (MVT) target area.
The project contains both structurally controlled and strata-bound mineralisation. Highest grade mineralisation is hosted within northerly-trending fault breccias and, to the west, by lower grade strata-bound mineralisation within sedimentary breccias. The mineralisation is believed to be controlled by growth faults which developed as splays off the major Halls Creek fault system.
Exploration for base metals in the Manbarrum Project area commenced in 1972 by Aquitaine and its Bonaparte Gulf JV partners. Exploration methods included detailed geophysical surveys, stream/soil geochemistry and drilling. By 1984 a total of 19 diamond drill holes and 50 percussion drill holes had been drilled in the region, providing the basis for resource calculations for the central zone.
In 1989 BHP entered the JV with Triako Resources, which had acquired the project from Aquitaine as part of a portfolio of tenements including the Sorby Hills base metals project in Western Australia, where the majority of work was subsequently focussed. In 1989 BHP completed an IP survey to the north of Manbarrum which demonstrated the prospectivity of the Burt Range Formation along the Sandy Creek trend. BHP subsequently drilled several diamond holes to test one of the IP anomalies 800 metres to the north.
Delta Gold farmed into the project during 1994 and conducted detailed gravity surveys and TEM soundings to provide evidence of depth to the prospective Upper Burt Range Formation dolomites. Delta concluded that gravity anomalies within the Burt Range dolerite had considerably increased the prospectivity of the Sandy Creek deposit, with the potential for extensions to the mineralised zone both north and south along strike to be tested by further drilling.
A major review of previous drilling in the eastern part of the Bonaparte Gulf Basin demonstrated that less than 4% of the drill holes in the area were effective in reaching their target, i.e., they intersected the entire topmost 50 metres of the Burt Range Formation (the principal host of Pb-Zn mineralisation).
All other holes had been collared too low in the sequence to intersect the entire favourable zone, or were in the hanging wall and had not penetrated far enough to intersect any or all of the favourable part of the Burt Range Formation.
In addition, a more restricted review covering the central zone of the Manbarrum Project area indicated that the main high-grade zone at Sandy Creek had not been fully drilled out, and that there was high potential for an open-pit of around 10-20 million tonnes @ 6-8% Pb and 2% Zn, within the main mineralised zone. This high-grade zone appears to be a near vertical fault related breccias zone, merging into a substantial gravity anomaly at its northern end, which is a particularly favourable target and has not been tested by effective drill holes.
Preliminary work suggests that the lead-zinc-silver mineralisation over much of the area is strata-bound and occurs within a fractured and slump brecciaed siltstone unit near the base of the Burt Range Formation.
Delta Gold attempted to address a lack of systematic geochemical data by implementing a regional geochemical program, as well as semi-detailed IP and gravity surveys and limited drilling. The results highlighted the exploration potential at the more recently defined North Ochre Mine prospect while also indicated potential to generate other targets away from known and tested areas.
Aboriginal Areas Protection Authority (AAPA)
AAPA issued an Amended Authority Certificate for the tenement area in 2006. This certificate allows the company to commence fieldwork over all of the Manbarrum tenements.
As a result of this amended certificate drilling commenced in September 2006.
Drill results will be released to the ASX on a regular basis and can be found in the ASX Announcements section.