The Ban Phuc intrusion is one of the larger ultramafic bodies in the region with dimensions of 940 by 420 metres. The intrusion is elongate with a northwesterly trend corresponding to the strike of the Devonian metasedimentary host rocks. It has intruded along the trend of a discontinuous unit of crystalline limestone. At its northwestern edge, only the flat lying base is preserved. The intrusion narrows and deepens to the southeast where it has an oval cross-section dipping steeply northeast and roughly concordant with the enveloping metasediments. A locally discordant southern contact with meta-sediments confirms the body is intrusive and not an extrusive komatiite.

Concave layering is defined by low-grade nickel-enriched sulphide layers, which are conformable with the base and walls of the intrusion. In the wider basal zone preserved at the northwestern end of the intrusion these are flat lying with only minor convexity, but in the southeastern section the layers are tightly oppressed and strongly concave, extending up the footwall and hanging walls of the intrusion. There is evidence in bedding attitudes along strike to the southeast of the intrusion for a synformal structure, suggesting that the strongly concave layering may arise from folding, with the ultramafic originally having formed a thinner sill roughly conformable with the sediments and now occupying the fold axis. The presence of cumulate sulphides along the base and walls of the intrusion indicate that it is upright, though folding, if it has occurred, is isoclinal and the hanging wall is overturned.

Massive sulphide mineralization occurs in a major shear controlled vein structure in hornfels host rock along the southern margin of the Ban Phuc intrusion. The vein is approximately 730 metres in length and is drill identified to 450 metres below surface. It has a northwesterly strike of 280-310? and is steeply dipping predominantly to the northeast. This vein cuts lithological layering in metasediments at a low angle but appears conformable in section. Offshoots and bifurcations are minor and the vein is largely a singular structure with evidence of structural thickening interpreted in places.

	Ban Phuc Plan View Geology		Ban Phuc Cross Section
	Massive Sulfide Vein: Conceptual Underground