Yabba dabba doo: Middle Island spins drill bit in NT

Middle Island Resources has hit the ground running as fast as Fred Flintstone’s feet with the completion of the first of three diamond drill holes at its Georgina project in the Northern Territory where it is testing for iron oxide-copper-gold (IOCG) potential.

The company recently kicked off its first round of drilling at Georgina – which features the Pebbles, Dino and Wilma IOCG targets that are all named after characters from the famous The Flintstones cartoon – and is expecting to drill three diamond drill holes between 600m and 650m deep.

The program constitutes Middle Island’s maiden testing of its priority Pebbles, Dino and Wilma targets, with Pebbles being the first cab off the rank in the current program.

The three targets were selected after an extensive program of identification, confirmatory and infill gravity surveys and comparative evaluations.

The processes finally distilled out several of what the company describes as “well-defined density anomalies” that are interpreted as being consistent with the densities, size and geometry of known IOCG examples or analogues. All of the targets are “blind”, meaning they do not outcrop and lie beneath recent surface cover and/or other post-mineralisation rock cover.

Initial logging and visual observations of core from the first diamond hole, which was drilled to 645.21m depth, shows it successfully intersected broad zones of haematite- and magnetite-altered intrusive basement rocks near the predicted depths. The company recorded narrow intervals containing trace copper and iron sulphides, mainly between 547m and 548m, 564m and 565m and intermittently from 616.6m to 645.21m at the end of the hole.

Such rock types could be consistent with the IOCG target concept as they reveal narrow intervals with trace iron and copper sulphides.

Additionally, the hole also bored through an overlying sequence of Georgina Basin fractured and brecciated carbonates and black shales containing narrow intercepts of minor lead, copper, iron and possible zinc sulphides, mainly in intervals between 227.5m and 231m, 270.4m and 271.4m and from 303.8m to 304.1m.

Middle Island Resources chief executive officer Roland Bartsch said: “The start to the drill program has progressed smoothly. While no visible economic mineralisation was intersected in the first hole, observed alteration and presence of minor copper sulphide is encouraging and a start from which to build as the first hole only tested a small part of the extensive Pebbles gravity anomaly that extends over several kilometres. The presence of observed base metal sulphides in the cover rocks is also an interesting development that opens new exploration possibilities in shallower target positions.”

A possible model for the overlying mineralisation could be the classic Mississippi Valley Type (MVT) of zinc and lead concentrations in carbonate sedimentary rocks where the ore minerals are typically sphalerite (zinc sulphide) and galena (lead sulphide), with other accessory minerals such as the iron sulphides, pyrite and marcasite.

MVT host rocks are typically sedimentary limestones and dolomitic rocks and their sulphides are commonly disseminated in pores and vugs. When in abundance, they tend to form massive to semi-massive beds that partially replace the carbonate hosts.

While it’s early days yet, the finding could mean that the Pebbles target could have an MVT deposit lurking beneath cover, in addition to further IOCG possibilities at greater depth.

At the very least, the hole looks to have confirmed the existence of potential ore metals in the systems encountered. But it is important to appreciate that the impressions are visual and await assay confirmation.

The Georgina project is part of Middle Island’s massive almost 7000-square-kilometre Barkly copper-gold “super project” that extends eastward from Tennant Creek and straddles the general area around the intersections of the Stuart, Barkly and Tablelands Highways at Tennant Creek in Australia’s Top End.

The drilling on the three IOCG targets at Georgina will be followed by testing of three sediment-hosted copper-zinc-lead-silver (SedH) targets in the company’s Bedrock and Tumbleweed prospects in its separate Barkly project that lies east of Georgina. Bedrock is likely to be the first target to feel the drill bit.

Both IOCG and SedH-type priority targets are accompanied by several lower-priority options distributed throughout the tenement groups that make up the Barkly super project.

Middle Island was awarded a maximum $300,000 under two co-funding grants – to test both the IOCG and SedH concepts – under the NT Government’s Geophysics and Drilling Collaborations program. The program is funded as part of the Resourcing the Territory initiative and is administered by the Northern Territory Geological Survey.

The drill rig has already begun drilling on the second IOCG target at Dino and once it and Wilma are completed, the company says its next round of drilling will test the Bedrock SedH prospect in the Barkly project, which received the second co-funding grant.

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