西太平洋高丰度高覆盖率多金属结核的发现受到各国学者的高度关注,如何高效探测不同覆盖率和丰度的多金属结核分布特征是目前研究的重点。利用EM122多波束回波强度资料对西太平洋海盆结核分布特征进行分析,结果表明,回波强度的高低变化...西太平洋高丰度高覆盖率多金属结核的发现受到各国学者的高度关注,如何高效探测不同覆盖率和丰度的多金属结核分布特征是目前研究的重点。利用EM122多波束回波强度资料对西太平洋海盆结核分布特征进行分析,结果表明,回波强度的高低变化与结核覆盖率关系密切,而当结核覆盖率相当时,回波强度的高低变化反映了结核的粒径大小,其中大型结核(直径D>6 cm)较多时,回波强度值明显增大。利用最大似然分类方法对回波强度资料进行监督分类,得出深海沉积物、低丰度、中等丰度和高丰度结核空间分布,结果显示,深海粘土沉积区与丰度>>30 kg/m2的高丰度结核分布区多回波强度差异高达近20 d B。展开更多
In 2001, the International Seabed Authority （ISBA） initiated the consideration relating to the Regulations for Prospecting and Exploration for Hydrothermal Polymetallic Sulphides and Cobalt-rich Ferromanganese Crust...In 2001, the International Seabed Authority （ISBA） initiated the consideration relating to the Regulations for Prospecting and Exploration for Hydrothermal Polymetallic Sulphides and Cobalt-rich Ferromanganese Crusts in the Area at its 7th session. Since then, the consideration of the Regulations has been mainly focused on the size of areas to be allocated for exploration and exploitation of the crusts. This paper, based on the investigation data and the analysis of the distribution characteristics of the crusts, suggests a model for determining the size of areas for exploration and exploitation of the crusts, taking into account various factors such as production scale, crust thickness and grade, mineable area proportion, recovery efficiency, exploration venture, and so on. Through the modeling, the paper suggests that the exploration area （the area covered by each application for approval of a plan of work for exploration of cobalt-rich crusts） shall be 4 856 km2 and the exploitation area （the mine site area） shall be 1 214 km2, for 20 years of 1 million wet tonnes annual production.展开更多
Submarine landslides have been observed in the Baiyun Depression of the South China Sea. The occurrence of hydrates below these landslides indicates that these slope instabilities may be closely related to the massive...Submarine landslides have been observed in the Baiyun Depression of the South China Sea. The occurrence of hydrates below these landslides indicates that these slope instabilities may be closely related to the massive release of methane. In this study, we used a simple Monte-Carlo model to determine the first-order deformation pattern of a gravitationally destabilizing slope. The results show that a stress concentration occurs due to hydrate dissociation on the nearby glide surface and on top of a gas chimney structure. Upon the dissolution of the gas hydrate, slope failure occurs due to the excess pore pressure generated by the dissociation of the gas hydrates. When gas hydrates dissociate at shallow depths, the excess pore pressure generated can be greater than the total stress acting at those points, along with the forces that resist sliding. Initially, the failure occurs at the toe of the slope, then extends to the interior. Although our investigation focused only on the contribution of hydrate decomposition to submarine landslide, this process is also affected by both the slope material properties and topography.展开更多
Shenhu Area is one of the most promising areas for gas hydrate exploration in the northern South China Sea (SCS). Pore water sulfate gradient, sulfate-methane interface (SMI) depth, and sulfate flux were analyzed at 5...Shenhu Area is one of the most promising areas for gas hydrate exploration in the northern South China Sea (SCS). Pore water sulfate gradient, sulfate-methane interface (SMI) depth, and sulfate flux were analyzed at 53 sites in this area. SO42 gradient ranges between 0.33 and 4.43 mmol L-1 m-1 . SMI depths are from 7.7 to 87.9mbsf. Sulfate flux varies between 2.0 and 26.9 mmol m-2 yr-1 , with a mean of 11.7 mmol m-2 yr-1 . Correlation coefficient between SMI depth and methane flux for the 53 sites is 0.80, implying that methane flux regulates the rate of anaerobic methane oxidation (AMO), SMI depth, and sulfate flux. Twelve anomalous fields with high methane flux and steep sulfate gradients were recognized. Bottom simulating reflector (BSR) is distributed mainly in areas where SMI depth is less than 50 mbsf or places with sulfate flux larger than 3.5 mmol m-2 yr-1 . It is suggested that the Baiyun Sag and the Southern Uplift are potential areas for gas hydrate exploration.展开更多
Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred i...Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred in limited areas of the slope. Drillings in the BSR-distributed area (the District S) on the northern slope of the South China Sea suggested that gas hydrate only occurred at Sites SH2, SH3, and SH7 with high saturation (up to 20%-40%), and there is no hydrate at Sites SH1 and SH5 although the distance between SH1 to SH3 is only 500m. In this paper, we investigated seafloor gradient, fault development, temperature, and pressure in the District S on the northern slope of the South China Sea to understand the possible factors con- trolling BSR distribution and gas hydrate occurrence. The District S is a structurally fractured continental slope zone and its seafloor gradient varied greatly. The BSR-occurred areas have an average gradient of 19.89×10 2 whereas the BSR-free zone has the average gradient of 10.57×10 2 . The calculated relative structural intensities from fault densities and displacements show that the BSR-distributed areas tend to occur in the areas with a moderately high structural intensity, where faults frequently developed close to the seafloor that are possibly favored for lateral migration of gases. On the basis of temperatures and pressures at drilling sites, hydrate-occurred Sites SH2, SH3, and SH7 are located within the thermodynamically stable area for methane hydrate, and hydrate-absent Sites SH1 and SH5 are out of the thermodynamically stable area for methane hydrate formation, suggesting that both BSR and the thermodynamic stability are necessary for hydrate occurrence in the subsurface.展开更多
文摘西太平洋高丰度高覆盖率多金属结核的发现受到各国学者的高度关注,如何高效探测不同覆盖率和丰度的多金属结核分布特征是目前研究的重点。利用EM122多波束回波强度资料对西太平洋海盆结核分布特征进行分析,结果表明,回波强度的高低变化与结核覆盖率关系密切,而当结核覆盖率相当时,回波强度的高低变化反映了结核的粒径大小,其中大型结核(直径D>6 cm)较多时,回波强度值明显增大。利用最大似然分类方法对回波强度资料进行监督分类,得出深海沉积物、低丰度、中等丰度和高丰度结核空间分布,结果显示,深海粘土沉积区与丰度>>30 kg/m2的高丰度结核分布区多回波强度差异高达近20 d B。
基金China International Seabed Area R & D Program under contract No.DYXM-115-01-1
文摘In 2001, the International Seabed Authority （ISBA） initiated the consideration relating to the Regulations for Prospecting and Exploration for Hydrothermal Polymetallic Sulphides and Cobalt-rich Ferromanganese Crusts in the Area at its 7th session. Since then, the consideration of the Regulations has been mainly focused on the size of areas to be allocated for exploration and exploitation of the crusts. This paper, based on the investigation data and the analysis of the distribution characteristics of the crusts, suggests a model for determining the size of areas for exploration and exploitation of the crusts, taking into account various factors such as production scale, crust thickness and grade, mineable area proportion, recovery efficiency, exploration venture, and so on. Through the modeling, the paper suggests that the exploration area （the area covered by each application for approval of a plan of work for exploration of cobalt-rich crusts） shall be 4 856 km2 and the exploitation area （the mine site area） shall be 1 214 km2, for 20 years of 1 million wet tonnes annual production.
基金supported by the National Science Foundation of China (No. 41306037) the National Science and Technology Works Special Project of the China Geological Survey (No. DD20160213)Qingdao National Laboratory for Marine Science and Technology (No. 2016ASKJ13)
文摘Submarine landslides have been observed in the Baiyun Depression of the South China Sea. The occurrence of hydrates below these landslides indicates that these slope instabilities may be closely related to the massive release of methane. In this study, we used a simple Monte-Carlo model to determine the first-order deformation pattern of a gravitationally destabilizing slope. The results show that a stress concentration occurs due to hydrate dissociation on the nearby glide surface and on top of a gas chimney structure. Upon the dissolution of the gas hydrate, slope failure occurs due to the excess pore pressure generated by the dissociation of the gas hydrates. When gas hydrates dissociate at shallow depths, the excess pore pressure generated can be greater than the total stress acting at those points, along with the forces that resist sliding. Initially, the failure occurs at the toe of the slope, then extends to the interior. Although our investigation focused only on the contribution of hydrate decomposition to submarine landslide, this process is also affected by both the slope material properties and topography.
基金supported by the National Basic Research Program of China (Grant Nos. 2009CB219508 and 2009CB219502)Research Program for Non-profit Industries of the Ministry of Land and Resources of the People’s Republic of China (Grant No. 200811014)
文摘Shenhu Area is one of the most promising areas for gas hydrate exploration in the northern South China Sea (SCS). Pore water sulfate gradient, sulfate-methane interface (SMI) depth, and sulfate flux were analyzed at 53 sites in this area. SO42 gradient ranges between 0.33 and 4.43 mmol L-1 m-1 . SMI depths are from 7.7 to 87.9mbsf. Sulfate flux varies between 2.0 and 26.9 mmol m-2 yr-1 , with a mean of 11.7 mmol m-2 yr-1 . Correlation coefficient between SMI depth and methane flux for the 53 sites is 0.80, implying that methane flux regulates the rate of anaerobic methane oxidation (AMO), SMI depth, and sulfate flux. Twelve anomalous fields with high methane flux and steep sulfate gradients were recognized. Bottom simulating reflector (BSR) is distributed mainly in areas where SMI depth is less than 50 mbsf or places with sulfate flux larger than 3.5 mmol m-2 yr-1 . It is suggested that the Baiyun Sag and the Southern Uplift are potential areas for gas hydrate exploration.
基金supported by National Basic Research Program of China(Grant No. 2009CB219508)Chinese Academy of Sciences (Grant No.KZCX2-YW-GJ03)National Natural Science Foundation of China(Grant No. 91228206)
文摘Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred in limited areas of the slope. Drillings in the BSR-distributed area (the District S) on the northern slope of the South China Sea suggested that gas hydrate only occurred at Sites SH2, SH3, and SH7 with high saturation (up to 20%-40%), and there is no hydrate at Sites SH1 and SH5 although the distance between SH1 to SH3 is only 500m. In this paper, we investigated seafloor gradient, fault development, temperature, and pressure in the District S on the northern slope of the South China Sea to understand the possible factors con- trolling BSR distribution and gas hydrate occurrence. The District S is a structurally fractured continental slope zone and its seafloor gradient varied greatly. The BSR-occurred areas have an average gradient of 19.89×10 2 whereas the BSR-free zone has the average gradient of 10.57×10 2 . The calculated relative structural intensities from fault densities and displacements show that the BSR-distributed areas tend to occur in the areas with a moderately high structural intensity, where faults frequently developed close to the seafloor that are possibly favored for lateral migration of gases. On the basis of temperatures and pressures at drilling sites, hydrate-occurred Sites SH2, SH3, and SH7 are located within the thermodynamically stable area for methane hydrate, and hydrate-absent Sites SH1 and SH5 are out of the thermodynamically stable area for methane hydrate formation, suggesting that both BSR and the thermodynamic stability are necessary for hydrate occurrence in the subsurface.
