The Beatons Creek Paleoplacer Gold Project, near the town of Nullagine in Western Australia, is one of Novo Resources' Pilbara Paleoplacer gold projects. At Beatons Creek, Novo is exploring for gold-bearing conglomerates within the Hardey Sandstone Formation, part of the Fortescue Group, a thick sequence of ancient sedimentary and volcanic rocks. Historic mines near the town of Nullagine exploited pyritic gold-bearing reefs as early as the late 1800's. Otherwise, the area has seen only very limited modern exploration. Through a 100% interest in certain tenements and a joint venture agreement with the Creasy Group on others (70% Novo, 30% Creasy Group), Novo is undertaking systematic exploration for gold-bearing reefs across this approximately 160 square kilometre project, employing large diameter diamond drilling, 50kg costean sampling and approximately 2 tonne bulk sampling to progress resource definition work.
Near the town of Nullagine, the Beatons Creek Formation is partially exposed along the Nullagine embayment, a 50-kilometer long north-trending half-graben extension of the Hammersley Basin up to approximately 30 km wide. Fortescue Group sedimentary and volcanic rocks filling the embayment are up to 3 kilometres thick, resting unconformably on ancient igneous and metamorphic rock of the Pilbara craton. Gold-bearing conglomerate horizons occurring within the Beatons Creek member of the Hardey Formation were exploited by historic mines near the town of Nullagine along the eastern margin of the embayment as early as the late 1800's.
Novo is focused on exploring for gold-bearing reefs within the Beatons Creek Formation. Previous explorers established the Beatons Creek Formation to be at least of 1,000m thick towards the southern part of the basin. Extensive outcropping ‘armoured lag’ type conglomerates make up the bulk of the mineralisation, and predominantly occurs in the top of the 1,000m sequence. Armoured lag is derived by marine reworking of a package of alluvial fan material by relative sea level movements. Material just below the wave base is winnowed out, removing smaller and more brittle clasts, such as sandstone and siltstone clasts. What remains are the larger resistive clasts, such as quartz, conglomerate ‘boulders’ (often stacked, resulting in an armoured lag), and buckshot pyrite. This process is also very efficient at concentrating gold in these lags. As the process is driven by ocean wave action, the system can be laterally extensive.
Additional mineralisation at the base of channels deposited in an alluvial fan setting is most pronounced in close proximity to the Pilbara craton basement contact. At Beatons Creek, this basement stratigraphy is the Mosquito Creek Formation, part of the De Grey Supergroup. Both the Mosquito Creek Formation and De Grey Supergroup are well endowed with small, but numerous high-grade deposits and form a likely source for detrital gold.
From 2011 through to 2017, Novo undertook systematic reverse circulation drill testing and costean sampling of the outcropping and subcropping conglomerates over an area of approximately 2km x 2km, drilling well over 35,000m of reverse circulation to better define the grade patterns and scale of this deposit.
In 2018, 27 deep PQ size diamond were drilled for a total of 4,482m to provide detailed 3D fault geometries and to establish a detailed mine stratigraphy. This was further tested and refined by collecting high resolution visual / acoustic downhole imagery from previously drilled reverse circulation holes over the project area. The mine stratigraphy allows for much better prediction of mineralisation and forms a 3D geological framework for further resource definition. Sixty-five targeted two-tonne bulk samples and 652 metres of jackhammered 50kg costean samples provide further grade definition to the model.
Definition of the Beatons Creek mine stratigraphy, by integrating historical data, diamond drilling, and detailed surface sampling has subdivided the 1,000m of conglomerates into a number of sequences, with most definition from denser drilling data in the top 300m.
The diamond drilling defined a visually distinctive ‘Beatons Upper’ sequence, laterally extensive gravels and pebble conglomerates with distinctive tuff horizons, providing a very reliable predictor of distance to mineralisation.
The ‘Beatons Mineralised’ sequence follows, merely 40m in thickness and containing the bulk of the Beatons Creek mineralisation amongst a package of predominantly cobble conglomerates. Mineralisation is laterally extensive in the two best defined marine lags (the M1 and M2 lag), recorded over 2km in strike length, although additional marine lags and several channel lodes were defined within this package. All mineralised marine and channel lags are visually definable and comprise of cobble to boulder conglomerates with increased amounts of resistive clasts and buckshot pyrite.
The ‘Beatons Middle’ package forms the bulk of the subsequent material. Visually similar to the Beatons Mineralised package with predominant cobble conglomerates it contains noticeably less pyrite (disseminated or buckshot) and several gravel or pebble conglomerate horizons can be recognized. Litho-geochemistry also highlights subtle changes. Some channel mineralisation is still defined within this package, but wider spaced and of lower tenor.
Several variations of a ‘Beatons Lower’ unit comprise the basal conglomerates which lacked mineral endowment. These comprise a lower felsic conglomerate unit, and an extensive lower pebble conglomerate.
Having constrained the bulk of mineralisation and continuous lags to within a narrow 40m thick package at a known distance below the several tuffs of the Beatons Upper unit allows for a much-improved geological model of mineralisation. An expanded wireframe model was constructed utilizing high-resolution data gathered from detailed diamond core logging and visual/acoustical imaging of reverse circulation drill holes. Such high-quality data allows for greater confidence in interpreting continuity of goldbearing conglomerate beds from one hole to the next while also allowing for tighter constraint of the upper and lower boundaries of each bed.
Oblique views of the current and updated wireframe models of gold-bearing conglomerate deposits [red] at Beatons Creek. Note the array of faults [blues and black] modeled in the lower image that define discrete domains.