Studies On Hydrothermal Circulation And Smokers Of Modern Seafloor Hydrothermal Activity

Geological information of all vent sites of modern seafloor hydrothermal activity found till now are researched systematically, such as geographical location, water depth, structural setting, activity, and so on. Deposit resource and biological features are summarized specially.Currently, plentiful and substantial achievements of seafloor hydrothermal activity research are gained. But, many deep-level questions still remain unsolved, mainly including: hydrothermal circulation, forming mechanism, mass evolution and hydrothermal biology, of them the first one is the key point. Process of hydrothermal circulation can be divided into 3 parts scientifically and reasonably, that is, (1) hydrothermal circulation under the seafloor, (2) hydrothermal circulation in the interface of seafloor and ocean (near vents), and (3) hydrothermal fluid entering the ocean (hydrothermal plume). According to flowing features and available data, applying conservation of mass, conservation of momentum, conservation of energy and hydrodynamics, mathematical model in every part is set up for the first time, and then initial conditions and boundary conditions of each model are determined, and numerical solution of equations are discussed respectively.Software Hydrotherm is recompiled and applied to model flow field of hydrothermal fluid in geological conditions. Some physical properties (for example, permeability, specific heat, etc.) do not keep constant in geological process, and changes of these parameters with temperature are considered for the first time. Systematically, hydrothermal circulations with different strata permeability structures and under different boundary conditions are analyzed for the first time. Firstly, pressure, enthalpy, temperature and velocity of pure water at different location of hydrothermal circulation system are described. Density and viscosity of fluid are calculated from temperature and pressure using properties of pure water. Secondly, influences of formational anisotropy and crack zone on hydrothermal circulation areanalyzed. Finally, hydrothermal circulation near critical state and with cooling pluton are modeled respectively.Finite Element software ANSYS are applied to analyze structure features and heat field of black smoker and white smoker for the first time. Effects of convective coefficients of inside and outside of smokers (reflecting disturbance of hydrothermal fluid and seafloor) on heat distribution of smoker are researched. Heat field of smoker with little lateral branch is analyzed. At the same time, flow fields with different shape, size, velocity and viscosity of fluid and Reynolds number in horizontal crack are discussed.On the base of contrasting and comparing current estimating method and estimated value of hydrothermal heat flux, exponential attenuation model are put forward to compute heat flux of hydrothermal activity. Using this method, calculated average heat flux of ocean crust is 69 mW/m2, and total heat flux of hydrothermal activity in global oceans is 4.11 X 1012 W. Whereas, values calculated from smokers and plumes are 9.7359 X 1010 W and 8.4895 X1010 W respectively.