A number of mud volcanoes exist in the southern Junggar Basin. To date few systematic studies on natural gas geochemistry of mud volcanoes have been conducted in China. In June 1991 and August 2010, the authors invest...A number of mud volcanoes exist in the southern Junggar Basin. To date few systematic studies on natural gas geochemistry of mud volcanoes have been conducted in China. In June 1991 and August 2010, the authors investigated the mud volcanoes in the southern Junggar Basin twice, and the mud volcanism weakened gradually as seen from the variations such as the decrease of gas pressure and output, the downthrow and dry up of the mud pool. The volcanic intensity was significantly weaker than that in Taiwan. The natural gas from the mud volcanoes in the southern Junggar Basin has similar geochemical characteristics, indicating the same source or origin. The main component of the mud volcano gas is alkane gas with contents of 91.15%-97.49%, and the gas is high-quality commercial gas since methane dominates in the alkane. The 513C1 values are -49.1‰-0.6‰, which are in accordance with the peak δ3C1 frequency of mud volcano gas around the world, and the alkane gas displays positive carbon isotopic series, i.e., δ3C1〈δ3C2〈δ13C3, suggesting typical thermogenic origin. The helium in the mud volcano gas is typically crust-derived due to the low R/Ra values of 0.011-0.054. The mud volcano gas is coal-derived since the δ13C2 values are all greater than -28‰, and C1/C1-4 and δ13C1 values are in accordance with those of natural gas derived from the Lower-Middle Jurassic coal-measures. Therefore, alkane gas from mud volcanoes in the southern Junggar Basin is mainly sourced from the Lower-Middle Jurassic coal-measures.展开更多
Since the eruption of the Tianchi volcano about 1000 years ago, there have been at least 3 to 5 eruptions of small to moderate size. In addition, hazardous avalanches, rock falls and debris flows have occurred during ...Since the eruption of the Tianchi volcano about 1000 years ago, there have been at least 3 to 5 eruptions of small to moderate size. In addition, hazardous avalanches, rock falls and debris flows have occurred during periods between eruptions. A future eruption of the Tianchi volcano is likely to involve explosive interaction between magma and the caldera lake. The volume of erupted magma is almost in a range of 0.1-0.5 km3. Tephra fallout may damage agriculture in a large area near the volcano. If only 1% of the lake water were ejected during an eruption and then precipitated over an area of 200 km2, the average rainfall would be 100 mm. Moreover, lahars are likely to occur as both tephra and water ejected from the caldera lake fall onto flanks of the volcano. Rocks avalanching into the caldera lake also would bring about grave hazards because seiches would be triggered and lake water with the volume equal to that of the landslide would spill out of the existing breach in the caldera and cause flooding downstream.展开更多
The tremendous development of Synthetic Aperture Radar(SAR)missions in recent years facilitates the study of smaller amplitude ground deformation over greater spatial scales using longer time series.However,this poses...The tremendous development of Synthetic Aperture Radar(SAR)missions in recent years facilitates the study of smaller amplitude ground deformation over greater spatial scales using longer time series.However,this poses greater challenges for correcting atmospheric effects due to the wider coverage of SAR imagery than ever.Previous attempts have used observations from Global Positioning System(GPS)and Numerical Weather Models(NWMs)to separate atmospheric delays,but they are limited by(1)The availability(and distribution)of GPS stations;(2)The low spatial resolution of NWM;And(3)The difficulties in quantifying their performance.To overcome these limitations,we have developed the Generic Atmospheric Correction Online Service for InSAR(GACOS)which utilizes the high-resolution European Centre for Medium-Range Weather Forecasts(ECMWF)products using an Iterative Tropospheric Decomposition(ITD)model.This enables the reduction of the coupling effects of the troposphere turbulence and stratification and hence achieves equivalent performances over flat and mountainous terrains.GACOS comprises a range of notable features:(1)Global coverage;(2)All-weather,all-time usability;(3)Available with a maximum of two-day latency;And(4)Indicators available to assess the model’s performance and feasibility.In this paper,we demonstrate some successful applications of the GACOS online service to a variety of geophysical studies.展开更多
Kueishan Tao (24°51′N, 121°55′E) is located at a tectonic junction of the fault system extension of Taiwan and the southern rifting end of the Okinawa Trough. A cluster of over 30 vents, at a water depth o...Kueishan Tao (24°51′N, 121°55′E) is located at a tectonic junction of the fault system extension of Taiwan and the southern rifting end of the Okinawa Trough. A cluster of over 30 vents, at a water depth of about 10-20 m off the eastern tip of the tao emits hy-drothermal fluids and volcanic gases such as H2S. A sulfur chimney or mound, formed by condensation of the sulfur contained in the hydrothermal fluid, can usually be seen around the vents. The tallest chimney reaches 6 m. Vents discharging a yellowish fluid have temperatures between 92 and 116 ℃ and flow rates as high as 158 t/h; vents discharging a whitish fluid have lower temperatures of between 48 and 62 ℃ and lower flow rates of about 7.0 t/h. These world-record, breaking low pH (as low as 1.52) fluids are totally different from those found in the black and white-chimneys of the mid-ocean ridges. Magnesium and SiO2 data indicate that these hydrothermal fluids probably originate from a depth of 915-1 350 m below the surface.While the ratios of major ions relative to the sodium of these hydrothermal fluids are quite similar to open ocean water, the ratios of SO4 and chloride to sodium seem to be higher for some of the vents. It is suggested that the volcanic gases contribute SO4 and chlorine to the fluids, hence increasing their ratios relative to sodium. Some hydrothermal fluids, however, are found to be depleted of the major elements which can have been caused by phase separation. The concentrations of iron and manganese in the fluids are much lower than those found in the mid-ocean ridges, while the aluminium content is higher. Four species of benthos (Xenograpsus testudi-natus, a snail, a sea anemone, and a Sipuncala), 1 species of algae (Corallinaceae), and 1 species of fish (Siganus fusescens) were recorded near the hydrothermal vents. A mitochondria DNA sequence comparison of Xenograpsus testudinatus with 6 other decapod species shows the greatest number of nitrogen base differences in the DNA fragments from 225 to 270. The gene diversity展开更多
文摘A number of mud volcanoes exist in the southern Junggar Basin. To date few systematic studies on natural gas geochemistry of mud volcanoes have been conducted in China. In June 1991 and August 2010, the authors investigated the mud volcanoes in the southern Junggar Basin twice, and the mud volcanism weakened gradually as seen from the variations such as the decrease of gas pressure and output, the downthrow and dry up of the mud pool. The volcanic intensity was significantly weaker than that in Taiwan. The natural gas from the mud volcanoes in the southern Junggar Basin has similar geochemical characteristics, indicating the same source or origin. The main component of the mud volcano gas is alkane gas with contents of 91.15%-97.49%, and the gas is high-quality commercial gas since methane dominates in the alkane. The 513C1 values are -49.1‰-0.6‰, which are in accordance with the peak δ3C1 frequency of mud volcano gas around the world, and the alkane gas displays positive carbon isotopic series, i.e., δ3C1〈δ3C2〈δ13C3, suggesting typical thermogenic origin. The helium in the mud volcano gas is typically crust-derived due to the low R/Ra values of 0.011-0.054. The mud volcano gas is coal-derived since the δ13C2 values are all greater than -28‰, and C1/C1-4 and δ13C1 values are in accordance with those of natural gas derived from the Lower-Middle Jurassic coal-measures. Therefore, alkane gas from mud volcanoes in the southern Junggar Basin is mainly sourced from the Lower-Middle Jurassic coal-measures.
基金The research was funded by the Natural Science Foundation of China(40172033)and the state volcano program of the tenth Five-Year Plan period(2001BA601B06-01-4).
文摘Since the eruption of the Tianchi volcano about 1000 years ago, there have been at least 3 to 5 eruptions of small to moderate size. In addition, hazardous avalanches, rock falls and debris flows have occurred during periods between eruptions. A future eruption of the Tianchi volcano is likely to involve explosive interaction between magma and the caldera lake. The volume of erupted magma is almost in a range of 0.1-0.5 km3. Tephra fallout may damage agriculture in a large area near the volcano. If only 1% of the lake water were ejected during an eruption and then precipitated over an area of 200 km2, the average rainfall would be 100 mm. Moreover, lahars are likely to occur as both tephra and water ejected from the caldera lake fall onto flanks of the volcano. Rocks avalanching into the caldera lake also would bring about grave hazards because seiches would be triggered and lake water with the volume equal to that of the landslide would spill out of the existing breach in the caldera and cause flooding downstream.
基金National Natural Science Foundation of China(No.41941019)Fundamental Research Funds for the Central Universities(Nos.300102260301/087,300102260404/087)。
文摘The tremendous development of Synthetic Aperture Radar(SAR)missions in recent years facilitates the study of smaller amplitude ground deformation over greater spatial scales using longer time series.However,this poses greater challenges for correcting atmospheric effects due to the wider coverage of SAR imagery than ever.Previous attempts have used observations from Global Positioning System(GPS)and Numerical Weather Models(NWMs)to separate atmospheric delays,but they are limited by(1)The availability(and distribution)of GPS stations;(2)The low spatial resolution of NWM;And(3)The difficulties in quantifying their performance.To overcome these limitations,we have developed the Generic Atmospheric Correction Online Service for InSAR(GACOS)which utilizes the high-resolution European Centre for Medium-Range Weather Forecasts(ECMWF)products using an Iterative Tropospheric Decomposition(ITD)model.This enables the reduction of the coupling effects of the troposphere turbulence and stratification and hence achieves equivalent performances over flat and mountainous terrains.GACOS comprises a range of notable features:(1)Global coverage;(2)All-weather,all-time usability;(3)Available with a maximum of two-day latency;And(4)Indicators available to assess the model’s performance and feasibility.In this paper,we demonstrate some successful applications of the GACOS online service to a variety of geophysical studies.
文摘Kueishan Tao (24°51′N, 121°55′E) is located at a tectonic junction of the fault system extension of Taiwan and the southern rifting end of the Okinawa Trough. A cluster of over 30 vents, at a water depth of about 10-20 m off the eastern tip of the tao emits hy-drothermal fluids and volcanic gases such as H2S. A sulfur chimney or mound, formed by condensation of the sulfur contained in the hydrothermal fluid, can usually be seen around the vents. The tallest chimney reaches 6 m. Vents discharging a yellowish fluid have temperatures between 92 and 116 ℃ and flow rates as high as 158 t/h; vents discharging a whitish fluid have lower temperatures of between 48 and 62 ℃ and lower flow rates of about 7.0 t/h. These world-record, breaking low pH (as low as 1.52) fluids are totally different from those found in the black and white-chimneys of the mid-ocean ridges. Magnesium and SiO2 data indicate that these hydrothermal fluids probably originate from a depth of 915-1 350 m below the surface.While the ratios of major ions relative to the sodium of these hydrothermal fluids are quite similar to open ocean water, the ratios of SO4 and chloride to sodium seem to be higher for some of the vents. It is suggested that the volcanic gases contribute SO4 and chlorine to the fluids, hence increasing their ratios relative to sodium. Some hydrothermal fluids, however, are found to be depleted of the major elements which can have been caused by phase separation. The concentrations of iron and manganese in the fluids are much lower than those found in the mid-ocean ridges, while the aluminium content is higher. Four species of benthos (Xenograpsus testudi-natus, a snail, a sea anemone, and a Sipuncala), 1 species of algae (Corallinaceae), and 1 species of fish (Siganus fusescens) were recorded near the hydrothermal vents. A mitochondria DNA sequence comparison of Xenograpsus testudinatus with 6 other decapod species shows the greatest number of nitrogen base differences in the DNA fragments from 225 to 270. The gene diversity
