CONCLUSIONS

The sulfide textures of the BHMS deposit feeder system suggest a simple system where hydrothermal fluids were first transported from basement via a fault conduit (Fig. F13). From the conduit, hydrothermal fluids entered the sediment system along permeable sandy turbidite layers. These fluids then precipitated chalcopyrite and pyrrhotite as they cooled. Less permeable mud- and clay-rich layers effectively confined sulfide deposition to sedimentary pore spaces within the permeable sandy units. Sulfide veining in the mud-rich sediments resulted from elevated fluid pressures induced by sulfide precipitation within the sandy units or by fluid flow through existing fracture networks. Most subvertical veins provided only limited hydrothermal fluid transport, but several centimeter-wide, multistage sulfide veins provide evidence for effective transport of fluids vertically through the sediment pile. Continued precipitation of sulfides within the permeable units and within veins of the impermeable units resulted in the well-developed feeder system at Bent Hill.

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