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
The determination of the stable isotopes, δD, δ 18 O and δ 30 Si, values from hydrothermal chimneys in the Mariana Trough, the West Pacific, indicated that the pure siliceous chimneys with gentle data variation wer...The determination of the stable isotopes, δD, δ 18 O and δ 30 Si, 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.展开更多
Studies on the Mariana Trough basalts began in the early 1970s, and during the past two decades, they are getting deeper and deeper with the Deep Sea Drilling Project devoted to the back-arc and the trough.From the ea...Studies on the Mariana Trough basalts began in the early 1970s, and during the past two decades, they are getting deeper and deeper with the Deep Sea Drilling Project devoted to the back-arc and the trough.From the early 1980s to展开更多
The submarine hydrothermal activity, its occurrence, the minerals and the chemical features of the hydrothermal sulfides in the Mariana Trough are described. The mineral phases and their existing forms of the hydrothe...The submarine hydrothermal activity, its occurrence, the minerals and the chemical features of the hydrothermal sulfides in the Mariana Trough are described. The mineral phases and their existing forms of the hydrothermal products formed at high temperature and intermediate-low temperature are discussed. It has been considered that the hydrothermal activity in the Mariana Trough isa small-scale one, different from those on the mid-ocean ridges and in the deep fracture zones.展开更多
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.
文摘The determination of the stable isotopes, δD, δ 18 O and δ 30 Si, 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.
文摘Studies on the Mariana Trough basalts began in the early 1970s, and during the past two decades, they are getting deeper and deeper with the Deep Sea Drilling Project devoted to the back-arc and the trough.From the early 1980s to
文摘The submarine hydrothermal activity, its occurrence, the minerals and the chemical features of the hydrothermal sulfides in the Mariana Trough are described. The mineral phases and their existing forms of the hydrothermal products formed at high temperature and intermediate-low temperature are discussed. It has been considered that the hydrothermal activity in the Mariana Trough isa small-scale one, different from those on the mid-ocean ridges and in the deep fracture zones.
