Study of petrophysical properties of rocks in seafioor hydrothermal fields has great significance for inves- tigation of seafloor hydrothermal activities, especially for polymetallic sulfides prospecting. In the prese...Study of petrophysical properties of rocks in seafioor hydrothermal fields has great significance for inves- tigation of seafloor hydrothermal activities, especially for polymetallic sulfides prospecting. In the present study, based on the current experimental conditions, we conducted systematic experiments to measure the magnetic susceptibility, electrical resistivity, porosity, density, as well as acoustic wave velocity of seafloor rocks and sulfides. Subsequently, we measured the physical characteristics of hydrothermal sulfides, basalts and peridotites which were collected from newly discovered seafloor hydrothermal fields at 49.6°E, 50.5°E, 5 1°E, 63.5°E, and 63.9°E of the Southwest Indian Ridge （SWIR）. Previously available and newly collected data were combined to characterize the physical differences between polymetallic sulfides and rocks. We also discussed the impact of hydrothermal alteration on the bedrock and demonstrated how these petrophysical properties of rocks can help in geophysical prospecting of seafloor hydrothermal fields as indicators.展开更多
Suspended particle samples were collected at 11 stations on the shelf and slope regions of the Chukchi Sea and the central Arctic Ocean during the fifth Chinese National Arctic Research Expedition （summer 2012）. The...Suspended particle samples were collected at 11 stations on the shelf and slope regions of the Chukchi Sea and the central Arctic Ocean during the fifth Chinese National Arctic Research Expedition （summer 2012）. The particle concentration, total organic carbon （TOC）, total nitrogen （TN） and the isotopic composition of the samples were analyzed. The suspended particle concentration varied between 0.56 and 4.01 mg.Ll; the samples collected from the sea ice margin have higher concentrations. The organic matter content is higher in the shelf area （TOC： 9.78%-20.24%; TN： 0.91‰-2.31%）, and exhibits heavier isotopic compositions （δ13C： -23.29‰ to -26.33‰ PDB; δ15N： 6.14‰-7.78‰）, indicating that the organic matter is mostly marine in origin with some terrigenous input. In the slope and the central Arctic Ocean, the organic matter content is lower （TOC： 8.06%- 8.96%; TN： 0.46%-0.72%）, except for one sample （SR15）, and has lighter isotopic compositions （δ13C： -26.93‰ to -27.78‰ PDB; δ15N： 4.13‰-4.84‰）. This indicates that the organic matter is mostly terrestrially-derived in these regions. The extremely high amount of terrigenous organic matter （TOC： 27.94%; TN： 1.16%; δ13C： -27.43‰ PDB; δ15N： 3.81‰） implies that it was carried by transpolar currents from the East Siberian Sea. Material, including sea ice algae, carried by sea ice are the primary source for particles in the sea ice margins. Sea ice melting released a substantial amount of biomass into the shelf, but a large amount of detrital and clay minerals in the slope and the central Arctic Ocean.展开更多
Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot poi...Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot point of the continental slope(FOS), the central axial point, and the maximum depth point. A total of 48 topographical profiles that crosscut the continental slope have been used to determine the trends of the BOS and FOS(the BOS and FOS lines) in the East China Sea(ECS). The trend of central axial points in the OT has been similarly determined by analyzing 39 topographical profiles across the axis of the trough. The BOS line forms the boundary between the continental shelf and slope. In the ECS, the BOS line roughly follows the 200 m isobath, continuously in the northern and middle parts of the OT, but jumping about somewhat in the south. The FOS line is the boundary between the continental slope and the bottom of the trough. The depth of the FOS increases gradually from north to south in the OT. Intense incisions by canyons into the slope in the southern part of the trough have led to the complex distribution of FOS. Topographical profiles crosscutting the northern, middle, and southern parts of the OT exhibit features that include: a single W-shape, a composite W-shape, and a U-shape, respectively, which suggests that in the middle and northern parts of the trough the central axial points are always located on seamount peaks or ridges associated with linear seamounts, whereas in the south they are found in the center of en echelon depressions. The line formed by the central axial points is the east-west dividing line of the OT, which indicates that the trough is a natural gap that prevents the extension of ECS continental shelf to the east. The distributions of the BOS and FOS lines are influenced by fluctuation of sea levels and submarine canyons, whereas the distribution of axis lines is controlled by tectonics and deposition.展开更多
基金The National Basic Research Program of China (973 Program) under contract No.2012CB417305COMRA Major Project under contract No.DY125-11-R-01-05the National Natural Science Foundation of China under contract Nos 49906004 and 41104073
文摘Study of petrophysical properties of rocks in seafioor hydrothermal fields has great significance for inves- tigation of seafloor hydrothermal activities, especially for polymetallic sulfides prospecting. In the present study, based on the current experimental conditions, we conducted systematic experiments to measure the magnetic susceptibility, electrical resistivity, porosity, density, as well as acoustic wave velocity of seafloor rocks and sulfides. Subsequently, we measured the physical characteristics of hydrothermal sulfides, basalts and peridotites which were collected from newly discovered seafloor hydrothermal fields at 49.6°E, 50.5°E, 5 1°E, 63.5°E, and 63.9°E of the Southwest Indian Ridge （SWIR）. Previously available and newly collected data were combined to characterize the physical differences between polymetallic sulfides and rocks. We also discussed the impact of hydrothermal alteration on the bedrock and demonstrated how these petrophysical properties of rocks can help in geophysical prospecting of seafloor hydrothermal fields as indicators.
基金funded by the Chinese Polar Environment Comprehensive Investigation and Assessment Program (Grant no. CHINARE-03-02)
文摘Suspended particle samples were collected at 11 stations on the shelf and slope regions of the Chukchi Sea and the central Arctic Ocean during the fifth Chinese National Arctic Research Expedition （summer 2012）. The particle concentration, total organic carbon （TOC）, total nitrogen （TN） and the isotopic composition of the samples were analyzed. The suspended particle concentration varied between 0.56 and 4.01 mg.Ll; the samples collected from the sea ice margin have higher concentrations. The organic matter content is higher in the shelf area （TOC： 9.78%-20.24%; TN： 0.91‰-2.31%）, and exhibits heavier isotopic compositions （δ13C： -23.29‰ to -26.33‰ PDB; δ15N： 6.14‰-7.78‰）, indicating that the organic matter is mostly marine in origin with some terrigenous input. In the slope and the central Arctic Ocean, the organic matter content is lower （TOC： 8.06%- 8.96%; TN： 0.46%-0.72%）, except for one sample （SR15）, and has lighter isotopic compositions （δ13C： -26.93‰ to -27.78‰ PDB; δ15N： 4.13‰-4.84‰）. This indicates that the organic matter is mostly terrestrially-derived in these regions. The extremely high amount of terrigenous organic matter （TOC： 27.94%; TN： 1.16%; δ13C： -27.43‰ PDB; δ15N： 3.81‰） implies that it was carried by transpolar currents from the East Siberian Sea. Material, including sea ice algae, carried by sea ice are the primary source for particles in the sea ice margins. Sea ice melting released a substantial amount of biomass into the shelf, but a large amount of detrital and clay minerals in the slope and the central Arctic Ocean.
基金supported by Public Science and Technology Research Funds Project of Ocean(Grant No.201105001)Fundamental Project of Science and Technology(Grant No.2013FY112900)National Natural Science Foundation of China(Grant Nos.40506017,41206046)
文摘Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot point of the continental slope(FOS), the central axial point, and the maximum depth point. A total of 48 topographical profiles that crosscut the continental slope have been used to determine the trends of the BOS and FOS(the BOS and FOS lines) in the East China Sea(ECS). The trend of central axial points in the OT has been similarly determined by analyzing 39 topographical profiles across the axis of the trough. The BOS line forms the boundary between the continental shelf and slope. In the ECS, the BOS line roughly follows the 200 m isobath, continuously in the northern and middle parts of the OT, but jumping about somewhat in the south. The FOS line is the boundary between the continental slope and the bottom of the trough. The depth of the FOS increases gradually from north to south in the OT. Intense incisions by canyons into the slope in the southern part of the trough have led to the complex distribution of FOS. Topographical profiles crosscutting the northern, middle, and southern parts of the OT exhibit features that include: a single W-shape, a composite W-shape, and a U-shape, respectively, which suggests that in the middle and northern parts of the trough the central axial points are always located on seamount peaks or ridges associated with linear seamounts, whereas in the south they are found in the center of en echelon depressions. The line formed by the central axial points is the east-west dividing line of the OT, which indicates that the trough is a natural gap that prevents the extension of ECS continental shelf to the east. The distributions of the BOS and FOS lines are influenced by fluctuation of sea levels and submarine canyons, whereas the distribution of axis lines is controlled by tectonics and deposition.
