Chilwa Minerals starts infill and extensional drilling at Mposa heavy minerals target

Perth-based junior Chilwa Minerals (ASX: CHW) has commenced infill and extensional drilling at the Mposa target area within the advanced-stage Chilwa heavy mineral sands project in Malawi.

The 6000 metre campaign is designed to test the extent and lateral continuity of potential mineralisation at depth by twinning a series of existing holes and drilling new holes adjacent to the target.

The company plans to use a sonic rig to penetrate the water table and improve sample recoveries from previous aircore drilling which averaged less than 70%.

Milestone development

Managing director Cadell Buss said the campaign represented a milestone development for Chilwa.

“We will be seeking an improved understanding of the mineralisation at Mposa especially at depth which was not targeted in previous drilling due to inadequate equipment,” he said.

“Mposa comprises approximately 30% of the project’s total inferred mineral resource by tonnage, making it the largest deposit at Chilwa and the logical place to start our campaign.”

Inferred mineral resource

The Chilwa project has an existing total inferred mineral resource of 61.6 million tonnes of heavy mineral sands at 3.9% for 2.4Mt total heavy minerals at a 1% cut-off grade over 10 known deposits.

Mposa accounts for 19.4Mt of heavy mineral sands at 4.3%, for 830,000 tonnes total heavy minerals at a 1% cut-off grade.

The Mposa resource was determined from 340 holes averaging a depth of 6.23m, with the shallowest hole being 2m and the deepest being 11m.

Many of these holes remained in mineralisation due to the use of an aircore rig, which was unable to penetrate the water table.

Recoveries were also variable.

Mr Buss said the project’s attraction was based on a number of factors including a high-value heavy mineral assemblage; areas of high grade and low slime mineralisation; positive initial concept studies; potential end markets; access to existing rail lines and port facilities; exploration upside; and strong commodity prices.

Sonic rig benefits

The use of a sonic rig at Mposa is expected to improve sample recoveries and achieve deeper penetration into the target.

It allows for complete encapsulation of the sample within the core barrel to prevent drill holes from collapsing, thereby enhancing the recovery of intact samples.

Sonic drilling also enables operations to be conducted beneath the water table which is not possible using conventional methods.