Exceptionally thick, high-grade gold hits have indicated that there is far more mineralisation at the Bekajang prospect within Besra Gold’s (ASX:BEZ) Bau project than previously believed.

Hole BKDDH-27 returned intercepts of 10m grading 7.09 grams per tonne (g/t) gold from a down-hole depth of 8m including 2.6m at 20.81g/t gold from 15.1m, 2m at 8.81g/t gold from 40m, and 13m at 22.91g/t gold from 58m including 1m at 64g/t gold from 61m.

Not only are the grades in the deepest interval some of the highest documented at the project since modern exploration began, it also indicates a potentially very significant understorey of mineral endowment, separate and distinct from the shallow Bau Limestone – Pedawan Shale Contact (LSC) target.

The customary views of the tenor of mineral endowment associated with the LSC target has also been challenged by hole BKDDH-23 which intersected more than 22m of mineralisation including 9m grading 17.71g/t gold from 19m including 1.4m at 71.9g/t gold from 19.4m.

Deeper mineralisation

Besra Gold (ASX:BEZ) believes that while LSC mineralisation is dominantly stratigraphically controlled, deeper Bau mineralisation may have greater structural control which is possibly directly linked to a nearby intrusive that was interpreted from geophysical anomalies.

“The results of the BKDDH drilling program highlight just how little understood are the controls on mineral endowment within what is the most mature sector of the Bau Gold Field corridor that includes two very significant historical mines, Tai Parit and BYG,” chief executive officer Dr Ray Shaw said.

“The potential implications of the exceptional grades intercepted during our recent drilling, demand priority follow-up, and may lead to a fundamental revision and upgrade of Bekajang’s potential.”

Bau gold project

Bau is located about 30km from Kuching, Sarawak, at the western end of an arcuate metalliferous belt extending through Borneo that is associated with significant gold mining – including the 7Moz Kelian and 3Moz Mt Muro projects – in the Indonesian portion of the island.

The field itself is defined by a gold mineralisation system covering a 15km by 8km corridor where the company has already defined total resources of 72.6Mt grading 1.4g/t gold, or 3.3Moz of contained gold, within a number of discrete deposits.

Bekajang lies along a very prospective trend that includes the historical Bukit Young Gold (BYG) pit, which produced about 440,926t of ore at 4.51g/t until September 1992, and the Tai Parit mine that has recorded production of some 700,000oz of gold.

Historical drilling had previously allowed the company to define a high confidence Measured and Indicated Resource of 120,400oz of gold and an Inferred Resource of 524,000oz of gold.

Drilling challenging previous views

Besra Gold’s 21 hole drill program (BKDDH-12 to -30) totalling 1,402m focused on testing the northern flank and the southwest flank of the historical Bekajang tailings dam to provide the first comprehensive cored drilling of three distinct mineralisation targets.

This confirmed the highly variable nature of gold mineralisation at the shallow LSC target which was the subject of historical shallow reverse circulation holes.

Core analysis consistently shows higher gold tenor associated with more intensely altered host lithologies, typically found either at the LSC stratigraphic boundary itself or within the overlying Pedawan Formation, especially proximal to dyke intrusion and/or silica replacement.

The company expects these results to greatly assist in increasing the understanding of those mechanisms responsible for local occurrences of very shallow high grade zones of gold mineralisation.

Meanwhile, the four deepest holes BKDDH-27 to -30 were drilled to provide the first systematic evaluation of the extent of hydrothermal alteration beyond the uppermost units of the Bau Limestone.

While results for the last three wells are pending, BKDDH-27 has already confirmed the presence of exceptional gold mineralisation some 40m below, and distinct from, that associated with the overlying LSC.

This rich interval with visible gold – rarely seen in the Carlin-like mineralisation that dominates the Bau Gold Field corridor – is adjacent to intrusives which may have “super-charged” the hydrothermal alteration processes in order to accommodate its exceptional gold tenor.

Follow-up exploration

Besra will resume drilling in December with a rig capable of drilling holes deeper than 300m to undertake exploration and delineation of the deeper lead potential – especially associated with structuring controlling the DIGHEM identified intrusive located beneath the Bekajang tailings dam.

This will test the two alternate models that could significantly revise the prospectivity of Bekajang.

The first posits that a sub-vertical structural corridor provided a pathway for the preferential flow of mineral charged hydrothermal fluids upwards to endow the overlying LSC.

Alternatively, the deeper mineralisation in BKDDH-27 may reflect strata-bound relative permeability differences inherent within the Bau Limestone.

This might imply that the mineralised body is more stratigraphically, rather than structurally, controlled, in which case multiple stacked bodies of mineralisation may have developed.



This article was developed in collaboration with Besra Gold (ASX:BEZ), a Stockhead advertiser at the time of publishing.  

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.