Controls of surface topography on submarine and subaerial hydrothermal fluid flow and vent-site location

Bani Hassan, Nasser, Iyer, Karthik, Rüpke, Lars and Borgia, Andrea (2010) Controls of surface topography on submarine and subaerial hydrothermal fluid flow and vent-site location [Talk] In: AGU Fall Meeting 2010, 15.12.2010, San Francisco, California, USA .

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Abstract

OS34A-05:
Hydrothermal convection is an important process that occurs in the oceanic lithosphere as well as within continents where the geothermal gradient is high enough to drive fluid flow. This process efficiently mines heat from the lithosphere, sustains life in the otherwise bleak settings at oceanic depths and is associated with mineral deposits. Although recent focus on hydrothermal systems has greatly improved our understanding on how they work, the detailed effects of topography on these systems has largely been ignored. While the qualitative effects of topography on hydrothermal flow are largely known (e.g. Ingebritsen 2006), we here present results from systematic numerical modeling on the importance of topography for both, subaerial and submarine hydrothermal convection. The model is based on a 2-D Finite Element Method (FEM) solver for fully compressible, single-phase, porous media fluid flow and is used to simulate hydrothermal convection in a number of synthetic studies as well as for two case studies for the Lucky Strike vent field (submarine) and the Amiata volcano (subaerial). The results of synthetic studies using sinusoidal topography variations show that topography indeed has a profound effect on the distribution and flow field of the convection cells. In the submarine case, fluid venting occurs at the topographic highs while the recharge zones are restricted to the lows. For the subaerial scenarios, the opposite occurs where groundwater flow focuses venting at flank regions and the recharge zones are situated at the highs. For example, in the submarine case, ~90% of the hydrothermal fluids vent at upper 50% of topographic highs if the number of topographic highs equals the number of plumes in a flat-top reference simulation. The results show that the focusing effect into topographic highs (submarine) and lows (subaerial) is highly dependent on the wavelength and amplitude of topography, i.e. wavelengths that are too high or low result in venting at flanks or even topographic lows (submarine case). Amplitude also has a first-order effect of focusing the vent sites on topographic highs and lows. Another observation is that the wavelength of the topography affects the number of plumes generated in the model. These findings are confirmed in two case studies for the submarine Lucky Strike hydrothermal field on the Mid-Atlantic Ridge and the subaerial geothermal field of Amiata, Italy. In both case studies the predicted vent locations fit well with the observed ones.

Document Type: Conference or Workshop Item (Talk)
Keywords: Meeresgeologie; Heat flow; Hydrothermal systems; Midocean ridge processes; Seafloor morphology, geology, and geophysics; Ocean Sciences
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-JRG-B3 Seabed Resources
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Date Deposited: 07 Jan 2011 10:51
Last Modified: 23 Feb 2012 05:17
URI: http://oceanrep.geomar.de/id/eprint/10699

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