Influence of normal faults and basement topography on ridge-flank hydrothermal fluid circulation

Abstract

Summary Mid‐ocean ridge‐flank hydrothermal fluid circulation is drawing increasing attention since about 70 per cent of the advective heat flux through oceanic crust occurs on ridge flanks. Previous numerical studies have largely considered the effect of basement relief but ignored the role of normal faults, although it is well known that normal faults are pervasive in the ridge‐flank environment. This paper investigates the importance of normal faults and basement topography in controlling ridge‐flank hydrothermal convection. Numerical experiments are conducted using a sophisticated finite‐element software package JHU2D. A 2‐D conceptual model is constructed based on a variety of in situ geophysical data recently collected around the DSDP/ODP site 504B. Four scenarios are examined in which basement topography, and active and inactive normal faults are included. Numerical simulation results indicate the active normal faults that penetrate through the sediment layer to the seafloor are a key factor governing the sea water circulation and the thermal regime within the oceanic crust. The presence of these faults challenges the previously discovered correlation among the seafloor heatflow, bathymetry and basement relief. It is the spacing between adjacent faults that determines the wavelength of the heatflow variations. Basement relief becomes important only when there are no active faults present. Fluid circulation is thus then confined mainly within the pillow lavas layer and the seafloor heatflow anomalies therefore have the same wavelength as that of the basement topography.

Evidence for hydrothermal Archaea within the basaltic flanks of the East Pacific Rise

“…1B and C) that expose cross sections of subseafloor basalt normally hidden beneath marine sediment. These faults also penetrate ridge flank basement crust and may be natural conduits connecting ridge flank hydrothermal reservoirs to the ocean floor (Yang, 2002; Haymon et al ., 2005).…”

Basin-Scale Numerical Modeling to Test the Role of Buoyancy-Driven Fluid Flow and Heat Transfer in the Formation of Stratiform Zn-Pb-Ag Deposits in the Northern Mount Isa Basin

“…Several driving forces have been deemed responsible for basin-scale fluid flow, related to fluid density variations associated largely with gradients in temperature and salinity. Historically, heat-induced and salinity-driven fluid flow have been treated separately (e.g., Frind, 1982;Voss and Souza, 1987;Fisher and Becker, 1995;Yang and Edwards, 2000;Sharp et al, 2001;Yang, 2002). Only a few studies have considered the effects of thermally and salinity-induced buoyancy simultaneously (e.g., Rosenberg and Spera, 1992;Sarkar et al, 1995;Yang et al, 2004a;Oliver et al, 2006;Yang, 2006a).…”

Factors controlling free thermal convection in faults in sedimentary basins: implications for the formation of zinc–lead mineral deposits

“…Numerical modelling has proved useful for testing and comparing various hypotheses regarding subsurface fluid flow and the resulting geological processes (e.g. Raffensperger & Garven 1995a,b;Garven & Raffensperger 1997;Hayba & Ingebritsen 1997;Barrier et al 1999Barrier et al , 2001Yang & Edwards 2000;Yang 2002). In many cases, it may be the only available tool because geological processes, such as ore formation, occur too slowly in time and too widely in space to be directly observed in the field or laboratory.…”

“…Raffensperger & Garven 1995a,b; Garven & Raffensperger 1997; Hayba & Ingebritsen 1997; Barrier et al. 1999, 2001; Yang & Edwards 2000; Yang 2002). In many cases, it may be the only available tool because geological processes, such as ore formation, occur too slowly in time and too widely in space to be directly observed in the field or laboratory.…”