Abstract. The Lady Bountiful granitoid-hosted lode gold deposit, located in the mid-greenschist facies metamorphosed Ora Banda greenstone sequence, is hosted predominantly by the late-tectonic Liberty Granodiorite. Gold mineralisation is localised along quartz-veined, sinistral, brittle fault-zone(s) that transect the boundary between the Liberty Granodiorite and Mt Pleasant sill. Quartz vein textures indicate two stages of a single goldrelated vein-development event, with high-grade gold mineralisation restricted to the second stage. Ore minerals include pyrite, chalcopyrite, pyrrhotite, galena, sphalerite, Au-Ag-Bi-Pb-tellurides, and native gold. Fluid infiltration has resulted in narrow (< 1 m) bleached wallrock alteration envelopes to the fault zones comprising albite-K-mica + chlorite + calcite + futile assemblages. Temperature-pressure conditions varied from Stage I (300 ~ + 50~ ~ 2 kbar) to Stage II (250 ~ +_ 50 ~ ~ 0.5 to 2 kbar), with the hydrothermal fluid in both stages characterised by X(COj < 0.15 and moderate salinity ( ~ 1.28 m NaC1). Intermittent phase separation of Stage II mineralising fluids, initiated by pressure fluctuations in dilational sites, and/or fluid-dominated fluid:wallrock interaction, are invoked as the dominant depositional mechanisms. The granitoid-hosted Lady Bountiful lode gold deposit shares many features with other granitoidhosted lode gold deposits in the Yilgarn Craton and the Superior Province. Granitoid-hosted lode gold deposits, such as the Lady Bountiful deposit, provide additional evidence that the dominant control on the localisation of gold mineralisation within a granitoid host is structure, with competency contrasts playing a significant role. Furthermore, the hydrothermal wallrock alteration and orefluid chemistry characteristics of the granitoid-hosted lode gold deposits are comparable to those established for greenstone-hosted lode gold mineralisation.
* Present address:Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, S7N OWO Canada Late-Archaean granitoid-greenstone terranes contain numerous lode gold deposits hosted by a variety of lithologies in a variety of structural settings. The genesis of such lode gold deposits remains equivocal with models incorporating derivation of gold-bearing fluids via magmatic, metamorphic and/or mantle processes. The majority of this documentation and model-building has been based on description of sub-amphibolite-facies, greenstonehosted lode gold deposits, with little documentation of either granitoid-hosted and/or amphibolite-facies deposits. Several recent studies (e
