Influence of permeability on hydrothermal circulation in the sediment-buried oceanic crust  

作　　者：WANG Xingtao1,2, ZHAI Shikui1, MENG Fanshun1, LI Huaiming1, YU Zenghui1, SUN Ge1 & XUE Gang1 1 Marine Geoscience Institute, Ocean University of China, Qingdao 266003, China 2 Bureau of Ocean and Fishery, Weihai 264200, China 

出　　处：《Science China Earth Sciences》2006年第7期773-784,共12页中国科学（地球科学英文版）

基　　金：This work was supported by the National Project'973'(Grant No.G2000078503);the National Natural Science Foundation of China(Grant No.40246024)

摘　　要：Hydrothermal convection in the upper oceanic crust has been inferred to be a common and important process. Under the simplified conditions of planar boundaries, permeability provides a strong constraint on the pattern of circulation, the dimensions of convective cells and flow field of hydrothermal circulation. By applying an advanced numerical modeling method, to our knowledge, it is the first time to investigate convection as it is influenced by different strata permeability structures, formational anisotropy, fracture zone and cooling intrusion. The simplified geological model is com-posed of 3 layers, sedimentary layer, high permeable basement layer and low permeable basement layer from top to bottom. When permeability in high permeable layer is 10 times larger than that in sedimentary layer, convection occurs in high permeable layer. The pattern of hydrothermal circulation and flow velocity of hydrothermal fluid are strongly influenced by strata permeability structures, changes of permeability in high permeable basement layer, fracture zone and cooling intrusion. However, formational anisotropy relatively exerts weak influence on hydrothermal circulation, with the ratio up to 1.5 of vertical permeability to lateral permeability in high permeable layer. Fracture zone existing in basement is the most important factor affecting the circulation field. The effects of a local intrusion are limited to convection intensity above the intrusion and have little impact on the fluid flow on a regional scale. As the result of numerical modelling, key factors affecting the hydrothermal cir-culation are good permeable zone and long-term heat source, not including fluid source.Hydrothermal convection in the upper oceanic crust has been inferred to be acommon and important process. Under the simplified conditions of planar boundaries, permeabilityprovides a strong constraint on the pattern of circulation, the dimensions of convective cells andflow field of hydrothermal circulation. By applying an advanced numerical modeling method, to ourknowledge, it is the first time to investigate convection as it is influenced by different stratapermeability structures, formational anisotropy, fracture zone and cooling intrusion. The simplifiedgeological model is composed of 3 layers, sedimentary layer, high permeable basement layer and lowpermeable basement layer from top to bottom. When permeability in high permeable layer is 10 timeslarger than that in sedimentary layer, convection occurs in high permeable layer. The pattern ofhydrothermal circulation and flow velocity of hydrothermal fluid are strongly influenced by stratapermeability structures, changes of permeability in high permeable basement layer, fracture zone andcooling intrusion. However, formational anisotropy relatively exerts weak influence on hydrothermalcirculation, with the ratio up to 1.5 of vertical permeability to lateral permeability in highpermeable layer. Fracture zone existing in basement is the most important factor affecting thecirculation field. The effects of a local intrusion are limited to convection intensity above theintrusion and have little impact on the fluid flow on a regional scale. As the result of numericalmodelling, key factors affecting the hydrothermal circulation are good permeable zone and long-termheat source, not including fluid source.

关 键 词：HYDROTHERMAL circulation  permeability  OCEANIC crust  numerical model. 

分 类 号：P733.4[天文地球—物理海洋学]