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<p>The Beta-Hunt Au-Ni deposit hosts coinciding orogenic Au and komatiite-hosted Ni-Cu-(PGE) mineralisation. The close spatial relationship between the two diachronous mineralisation styles suggests that long-lived local structural architecture played a role in the superposition of the two deposit types. Deposit-scale field geological and structural analysis was conducted to define the deformation paragenesis and structural framework associated with Ni-Cu-(PGE) and Au mineralisation. Structural reconstruction suggests that komatiite-hosted Ni-Cu-(PGE) sulfides were preferentially deposited within a pre- or syn-magmatic SW-dipping growth fault array during early extension (D<sub>BH1</sub>), associated with a ~ 2700&#xa0;Ma regional SW-NE directed rifting event. During subsequent ~ 2690–2630&#xa0;Ma rift inversion (D<sub>BH2</sub>– D<sub>BH3</sub>), the early growth faults were reactivated by fluid-mediated deformation and were associated with brittle-ductile shearing and Au mineralisation. Early D<sub>BH2a</sub> horizontal shortening and ductile reactivation of D<sub>BH1</sub> growth faults resulted in the formation of shear zones hosting low-grade Au mineralisation. This was followed by a rotation of the local stress field to vertical shortening during D<sub>BH2b</sub>, synchronous with mean stress reduction and increased fluid pressure associated with an influx of hydrothermal fluids. The associated brittle reactivation of the shear zones caused the development of a D<sub>BH2b</sub> extension and hydraulic breccia vein network, which promoted advective open fracture fluid flow and the formation of high-grade to locally ultra-high-grade Au mineralisation. Structural inheritance and reactivation during subsequent deformation events were, therefore, key to the superposition of komatiite-hosted Ni-Cu-(PGE) and orogenic Au mineralisation at Beta-Hunt.</p>

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Structural controls of superposed komatiite-hosted Ni and orogenic Au mineralisation at Beta-Hunt, Western Australia

  • 期刊论文

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  • 发表日期：

    2025年8月7日

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  • Lauri T. Virnes,
  • Nicolas Thébaud,
  • Helen B. McFarlane,
  • Laura Petrella,
  • Denis Fougerouse,
  • Anne Brandt Virnes,
  • Laure Martin

摘要

The Beta-Hunt Au-Ni deposit hosts coinciding orogenic Au and komatiite-hosted Ni-Cu-(PGE) mineralisation. The close spatial relationship between the two diachronous mineralisation styles suggests that long-lived local structural architecture played a role in the superposition of the two deposit types. Deposit-scale field geological and structural analysis was conducted to define the deformation paragenesis and structural framework associated with Ni-Cu-(PGE) and Au mineralisation. Structural reconstruction suggests that komatiite-hosted Ni-Cu-(PGE) sulfides were preferentially deposited within a pre- or syn-magmatic SW-dipping growth fault array during early extension (DBH1), associated with a ~ 2700 Ma regional SW-NE directed rifting event. During subsequent ~ 2690–2630 Ma rift inversion (DBH2– DBH3), the early growth faults were reactivated by fluid-mediated deformation and were associated with brittle-ductile shearing and Au mineralisation. Early DBH2a horizontal shortening and ductile reactivation of DBH1 growth faults resulted in the formation of shear zones hosting low-grade Au mineralisation. This was followed by a rotation of the local stress field to vertical shortening during DBH2b, synchronous with mean stress reduction and increased fluid pressure associated with an influx of hydrothermal fluids. The associated brittle reactivation of the shear zones caused the development of a DBH2b extension and hydraulic breccia vein network, which promoted advective open fracture fluid flow and the formation of high-grade to locally ultra-high-grade Au mineralisation. Structural inheritance and reactivation during subsequent deformation events were, therefore, key to the superposition of komatiite-hosted Ni-Cu-(PGE) and orogenic Au mineralisation at Beta-Hunt.