Hydrothermal chimney is a product of hydrothermal activity on the seabed. Chimney samples dredged from Jade hydrothermal area in Izena depression of the Okinawa Trough, are characterized by relatively enriched light r...Hydrothermal chimney is a product of hydrothermal activity on the seabed. Chimney samples dredged from Jade hydrothermal area in Izena depression of the Okinawa Trough, are characterized by relatively enriched light rare earth elements (LREE) and strongly positive Eu anomalies. 87Sr/86Sr and 143Nd/144Nd of these samples are exactly between those of seawater and of acidic pumice, averaged at 0.708928 and 0.512292, respectively. These characteristics imply that the main source of hydrothermal sulfide at Jade area is possibly the undersurface acidic rocks. The mineralizing mechanism can be summarized as follows: Large amount of mineralized material would be leached out and LREE-enriched hydrothermal solution would be subsequently produced as a result of thermo-chemical exchange reaction between acidic volcanic rocks and heated seawater that penetrated in advance from upper water mass. The spurting out from the seabed and quickly crystallizing in the seawater of hydrothermal solution are responsible for the formation of Cu-Zn sulfide and barite-amorphous SiO2 minerals that are characterized by enriched LREE and positively strong Eu anomalies.展开更多
The determination of the stable isotopes, δD, δ18 and δ30, values from hydrothermal chimneys in the Mariana Trough, the West Pacific, indicated that the pure siliceous chimneys with gentle data variation were forme...The determination of the stable isotopes, δD, δ18 and δ30, values from hydrothermal chimneys in the Mariana Trough, the West Pacific, indicated that the pure siliceous chimneys with gentle data variation were formed in low temperature environment. It reflects that the sea-floor hydrothermal activity of the Mariana Trough is primarily low-to-medium temperature hydrothermal eruption, and those chimneys with strong data variation and containing pyrite were formed in higher temperature environment. Key words Mariana Trough - stable isotope - geochemistry - hydrothermal chimney - genetic type Project 49876016 supported by NSFC.展开更多
Microtextures and struetures of 9 hydrothermal chimneys sampled on the small spreading ridge Of the Mari ana Trough during SONNE Cruise 57 (SO57) and 69 (SO69) in 1988 and 1990 were studied by means of scanning elec...Microtextures and struetures of 9 hydrothermal chimneys sampled on the small spreading ridge Of the Mari ana Trough during SONNE Cruise 57 (SO57) and 69 (SO69) in 1988 and 1990 were studied by means of scanning electron microscope. The results reveal that the two types of chimneys from the Mariana Trough. the 'silicic chimneys' containing Fe sulfide and the pure 'silica chimneys' without sulfide, vary distinctly not only in mineral and chemical compositions, but also in microtextures and structures. The silicic chimneys generally show three major types of microtextures.The inside of the chimneys is dominated by holocrystalline or semicrystalline idiomorphic and hypidiomorphic granular textures and the outwall by amorphous colloidal texture. In some of the silicic chimneys relict texture is observed. However,the pure silica chimneys show chiefly amorphous colloidal texture from the inside to the outwall. Microstructurally. theinside of the silicic chimneys is dominated by a 'silica-covering' structure and a 'voidfilling' structure, and the outwall by a chain-like or three-dimentional chain-network structure built up by individual opal globules, whereas the pure silica chimneys are mainly three-dimentional chain-network and the dense silica bands in structure. These variations suggest that not only mineralizing conditions but also processes differ distinctly during the formation of the two types of chimneys, and that hydrothermal mineralization in the Mariana Trough shows a multistage or multieplsodical nature.展开更多
Polymetallic sulfides from two hydrothermal chimneys and talus deposit from the Vienna Woods field of Manus Basin were studied for mineralogy,elemental composition,and S-isotope ratio to understand their evolution.The...Polymetallic sulfides from two hydrothermal chimneys and talus deposit from the Vienna Woods field of Manus Basin were studied for mineralogy,elemental composition,and S-isotope ratio to understand their evolution.The factors including the nature of source fluid,mineral paragenesis,and related geochemical processes have been discussed.Mineralogy and elemental concentration of Cu and Fe-rich large chimney at the central part of this hydrothermal field was completely different from the smaller Zn-rich peripheral chimney and Fe-rich talus deposit,suggesting the variable degree of alterations generate physico-chemically different source fluids responsible for these hydrothermal structures.Similarly,S-isotope ratios also indicate chemically diverse fluids and different modes of precipitation were involved in their evolution.Distinct mineral zonings and associated elemental and isotopic compositions within individual deposit confirm paragenetic shifts were involved during their growth process.展开更多
基金This study was supported by the National Natural Science Foundation of China under the contract No.40276024 and 49873015.
文摘Hydrothermal chimney is a product of hydrothermal activity on the seabed. Chimney samples dredged from Jade hydrothermal area in Izena depression of the Okinawa Trough, are characterized by relatively enriched light rare earth elements (LREE) and strongly positive Eu anomalies. 87Sr/86Sr and 143Nd/144Nd of these samples are exactly between those of seawater and of acidic pumice, averaged at 0.708928 and 0.512292, respectively. These characteristics imply that the main source of hydrothermal sulfide at Jade area is possibly the undersurface acidic rocks. The mineralizing mechanism can be summarized as follows: Large amount of mineralized material would be leached out and LREE-enriched hydrothermal solution would be subsequently produced as a result of thermo-chemical exchange reaction between acidic volcanic rocks and heated seawater that penetrated in advance from upper water mass. The spurting out from the seabed and quickly crystallizing in the seawater of hydrothermal solution are responsible for the formation of Cu-Zn sulfide and barite-amorphous SiO2 minerals that are characterized by enriched LREE and positively strong Eu anomalies.
文摘The determination of the stable isotopes, δD, δ18 and δ30, values from hydrothermal chimneys in the Mariana Trough, the West Pacific, indicated that the pure siliceous chimneys with gentle data variation were formed in low temperature environment. It reflects that the sea-floor hydrothermal activity of the Mariana Trough is primarily low-to-medium temperature hydrothermal eruption, and those chimneys with strong data variation and containing pyrite were formed in higher temperature environment. Key words Mariana Trough - stable isotope - geochemistry - hydrothermal chimney - genetic type Project 49876016 supported by NSFC.
文摘Microtextures and struetures of 9 hydrothermal chimneys sampled on the small spreading ridge Of the Mari ana Trough during SONNE Cruise 57 (SO57) and 69 (SO69) in 1988 and 1990 were studied by means of scanning electron microscope. The results reveal that the two types of chimneys from the Mariana Trough. the 'silicic chimneys' containing Fe sulfide and the pure 'silica chimneys' without sulfide, vary distinctly not only in mineral and chemical compositions, but also in microtextures and structures. The silicic chimneys generally show three major types of microtextures.The inside of the chimneys is dominated by holocrystalline or semicrystalline idiomorphic and hypidiomorphic granular textures and the outwall by amorphous colloidal texture. In some of the silicic chimneys relict texture is observed. However,the pure silica chimneys show chiefly amorphous colloidal texture from the inside to the outwall. Microstructurally. theinside of the silicic chimneys is dominated by a 'silica-covering' structure and a 'voidfilling' structure, and the outwall by a chain-like or three-dimentional chain-network structure built up by individual opal globules, whereas the pure silica chimneys are mainly three-dimentional chain-network and the dense silica bands in structure. These variations suggest that not only mineralizing conditions but also processes differ distinctly during the formation of the two types of chimneys, and that hydrothermal mineralization in the Mariana Trough shows a multistage or multieplsodical nature.
基金The GEOSINK project funded by CSIR,Indiathe CSIR-NIO contribution No.6111
文摘Polymetallic sulfides from two hydrothermal chimneys and talus deposit from the Vienna Woods field of Manus Basin were studied for mineralogy,elemental composition,and S-isotope ratio to understand their evolution.The factors including the nature of source fluid,mineral paragenesis,and related geochemical processes have been discussed.Mineralogy and elemental concentration of Cu and Fe-rich large chimney at the central part of this hydrothermal field was completely different from the smaller Zn-rich peripheral chimney and Fe-rich talus deposit,suggesting the variable degree of alterations generate physico-chemically different source fluids responsible for these hydrothermal structures.Similarly,S-isotope ratios also indicate chemically diverse fluids and different modes of precipitation were involved in their evolution.Distinct mineral zonings and associated elemental and isotopic compositions within individual deposit confirm paragenetic shifts were involved during their growth process.
