Yangibana Geology

The Yangibana Project covers a majority of the Gifford Creek Ferrocarbonatite Suite (GCFS). The GCFS is located within the Gascoyne Province of the Capricorn Orogen, between the Archaean Yilgarn Craton to the south, and the Archaean Pilbara Craton to the north. The Gascoyne Province, which consists of a suite of Archaean to Proterozoic gneisses, granitic and metasedimentary rocks is overlain by the Paleoproterozoic Ashburton Formation to the north, the Mesoproterozoic Edmund and Collier Basins to the east, and the Phanerozoic Carnarvon Basin to the west .

Locally, the tenement area consists of granitic rocks of the 1680-1620 Ma Durlacher Supersuite, specifically the Pimbyana and Yangibana Granites, which contain rafts of sedimentary rocks including arenites, calc-silicates, and quartzites of the 1760-1680 Ma Pooranoo Metamorphics. These rocks are intruded by sills, dykes, and veins of ferrocarbonatite and ironstone, and associated fenitic alteration, which comprise the 1,300-1,280 Ma GCFS.

The Yangibana Project area has been subject to several distinct tectonothermal cycles of which the Mangaroon Orogeny (1680-1620Ma), the Mutherbukin Tectonic Event (1385-1200Ma) and the Edmundian Orogen (1030-955Ma) are the most significant. During the Mangaroon Orogeny, intense deformation and metamorphism were coincident with the intrusion of the Durlacher Supersuite. The ferrocarbonatites that occur within the project area have been dated at 1262-986Ma, dates coincident with both the Mutherbukin Tectonic Event and the Edmundian Orogeny. The Lyons River Fault, which is a deep crustal lineament that has been traced to the Mohorovicic discontinuity, may have acted as a fluid conduit during these events, resulting in the emplacement of the ferrocarbonatites and associated hydrothermal alteration over a period of several hundred million years.

The GCFS is dominated by two major southeast trending shear zones, which are cross-cut by multiple north-south to north-east trending faults. The northern shear zone, the Bald Hill Lineament, is anastomosing and variable in width, comprising multiple fault splays. Geophysical interpretation by Southern Geoscience Consultants during 2016 indicated that the Bald Hill Lineament separates an early, highly fractured granite to the north from folded Pooranoo Metamorphics to the south.

The southern shear zone, the Lyons River Fault, is less complex and relatively narrow, forming the boundary between the Edmund Group, and an early granite to the north.

The Pooranoo Metamorphics are multiply-folded along southeast trending axes. In the north-west of the area of interest these folds are generally wide with granite cores. This area of wider folding has also been intruded by a later granite.

One of the key features of the GCFS within the project area is the widespread occurrence of ironstone dykes that are spatially associated with the ferrocarbonatite intrusions. The ironstone dykes are surrounded by relatively narrow haloes of fenitic alteration, and locally associated with quartz veining. Fenitic alteration haloes are characterised by the presence of feldspars and/or Na-amphiboles and magnetite. The ironstone dykes, with dominant north, northeast and west-northwest trends, consist predominantly of goethite, hematite, and magnetite, and are locally weakly radioactive. The ferrocarbonatites and ironstones of the GCFS occur as sinuous pods and veins generally less than 10m wide, that are traceable cumulatively for up to 25 kilometres. The ironstones of the GCFS have historically been the focus of exploration activity in the area, due to enrichment in Rare Earths Elements (REE).

Rare earths mineralisation at Yangibana is predominantly hosted by monazite, a phosphate mineral. Initial petrological assessment of samples of mineralised carbonatite from Yangibana North, identified the monazite as being the Ce-rich end-member, Ce-monazite. With the acquisition of further data from other areas within the project area, significant variations in the Nd content from prospect to prospect were identified. Prospects in the Eastern Belt of mineralisation (Bald Hill, Fraser’s, Auer, and Auer North) were identified as having significantly higher Nd content than prospects within the Western Belt of mineralisation (Yangibana West to Kane’s Gossan) suggesting that monazite may vary throughout the project area from the Ce-monazite variant, toward more Nd-rich variants (Nd-monazite).

Petrology and mineralogy has identified additional rare earths-bearing phosphates, mainly bastnasite with lesser aluminium phosphates (gorceixite, florencite and rhabdophane). Fluorapatite occurs as subordinate rare earths-bearing mineral in the ironstones but is more often found in the fenite haloes.

The dominant lithologies in the tenement area are granites of the Durlacher Supersuite. Rafts of older sedimentary rocks occur within these intrusives.

The primary mineralisation targets within the Yangibana Project are narrow, discontinuously but regionally extensive outcropping ironstone dykes that carry anomalous rare earths associated with monazite mineralisation. The project also has the potential for as yet untested rare earths mineralisation associated with deeper carbonatite bodies.

Previous exploration at Yangibana has included reverse circulation drilling in the 1980s at a number of prominent targets, all now within Hastings’ current tenements, and on the basis of this drilling a non-JORC resource of 3.5 million tonnes at 1.63%TREO was estimated by a previous explorer. The vast majority of this resource lies in the near surface oxidised zone.

The ironstones are now considered to be a younger intrusive phase that has cut across slightly older ferrocarbonatite dykes, possibly leaching and upgrading rare earths (and base metals) from them. The carbonatite dykes themselves, along with the associated fenitic alteration, are considered to be sourced from an as yet undiscovered carbonatite intrusion which could potentially host significant rare earths and possibly base metals. Hastings tenements now total almost 650 sq km, covering the bulk of the Gifford Creek Ferrocarbonatite Complex.

Hastings has completed seven drilling programmes at the Yangibana Project, testing a number of targets throughout its major tenement holding.

On this basis of this drilling a JORC Resource estimation has been completed by independent consultant Lynn Widenbar and Associates Pty Limited and this was reported in November 2017.

The current total diluted resources for the Yangibana Project are:-

CategoryTonnesNd2O3+Pr6O11TREONd2O3Pr6O11
%%ppmppm
Measured3,900,0000.421.193,370850
Indicated8,600,0000.421.253,370860
Inferred8,400,0000.361.092,830740
Total21,000,0000.401.173,150810

Click here for Yangibana JORC Resources

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