Recent fluid monitoring work shows that the contents of mantle-derived CO2, He and CH4 increased anomalously in 2002 and 2003. The ^3He/^4He ratio of the deep-fault-type Jinjiang hot springs increased highly anomalous...Recent fluid monitoring work shows that the contents of mantle-derived CO2, He and CH4 increased anomalously in 2002 and 2003. The ^3He/^4He ratio of the deep-fault-type Jinjiang hot springs increased highly anomalously in 2003, and then decreased in 2004. The ^3He/^4He ratio from the thermal-reservoir-type Changbaijulong hot springs increased slowly in 2003, and the increase continued in 2004. The mantle-derived He content of the He released from the Changbaijulong springs increased obviously in 2004. The anomaly of the released gases and the isotopic He was consistent with the trends of seismic activities in the Tianchi volcanic area between 2002 and 2004. The abnormal release of the Jinjiang hot springs apparently decreased after the seismic activities ceased in the second half of 2004, while the abnormal release from the Changbaljulong increased significantly after these seismic activities. It shows that the abnormal release of magmas-derived gases from the thermal-reservoir-type springs lags behind that of the deep-fault-type springs. These characteristics may be of great significance for identifying deep magmatic activity and predicting volcanic earthquakes in the future.展开更多
Objective The Tengchong volcanic field is situated along the southeastern margin of the Tibetan Plateau and adjacent to the border area of western Yunnan Province of China and Myanmar.Affected by the intense tectonic ...Objective The Tengchong volcanic field is situated along the southeastern margin of the Tibetan Plateau and adjacent to the border area of western Yunnan Province of China and Myanmar.Affected by the intense tectonic stress of subduction of the Indian plate to Eurasian plate,this volcanic field has experienced strong volcanism.展开更多
This paper deals with geochemical features of gas emitted from the Hubin Springs. The Hubin Springs zone, a strong thermal emission zone, is are locatedd at the north edge of the Tianchi caldera lake. Very young depos...This paper deals with geochemical features of gas emitted from the Hubin Springs. The Hubin Springs zone, a strong thermal emission zone, is are locatedd at the north edge of the Tianchi caldera lake. Very young deposits with uncertain eruption date are found on the top area of the Tianwenfeng, which might have been formed in one of the recent eruptions or the Millennium Eruption. It is of significance to study the geochemistry features of the emitting gas from the Hubin Springs to understand the activities of the Tianchi Volcano. This paper systematically sampled and analyzed the gases emitted from the Hubin Springs and discussed their geochemistry features. The results show that there is a high content of deep derived gases, such as CO2, He, CH4 and Ar in Hubin Springs zone. The isotopic ratio of He lies between 4. 18 and 5. 95 Ra. The averaged mantle derived gas content calculated from the ^4He/2^20Ne ratio and He content reaches 67.1%. All these show that the Hubin Springs are located on a special belt of deep gases released in high intensity and large scale. The spatial distribution of Helium isotope is characterized by concavity, showing that this special area may be related to the volcanic edifice. It is highly possible that the released gases represent the residual gas samples of the latest eruptions from the Tianchi Volcano. However more detailed studies are demanded.展开更多
The huge comendite ignimbrite-forming eruption of Tianchi Volcano maintained a stable plinian column during its earlier stage of eruption, and succeeded a collapsing of the column producing pumiceous ignimbrite deposi...The huge comendite ignimbrite-forming eruption of Tianchi Volcano maintained a stable plinian column during its earlier stage of eruption, and succeeded a collapsing of the column producing pumiceous ignimbrite deposits. It is estimated that the column height (Hb) varied from 20km to 10km in its eruption period, with a maximum height of 25km in the eruption peak. Its umbrella cloud spread into the stratosphere with a top height of 35km (Ht). The dense lithics whose diameter exceeded 8cm followed a ballistics trajectory in a 3km-high gas thrust region, while the smaller lithics and pumices entered the convection region in the column. The initial magma temperature was 780℃. The comendite magma had an exit velocity of 300m/s, volatile content of about 1wt% and lithics of 8.5wt%. From a 400m-wide vent the magma was expelled out with a mass eruption rate of 108.36kg/s, corresponding to a volume rate of 104.95m 3/s. Over 1.3436×10 19 J of energy had been released from Tianchi Volcano, of which the kinetic proportion was about 8%. The plume had a temperature of -50℃ at the base focus of the cloud and a upward speed of 215m/s. The cloud spread out at a gradually downspeed with the increasement of distance from its center. For example, at a distance of 25km from its center the spreading velocity is about 250m/s, and is about 60m/s at distance of 100km. The main part of the plinian column, that is the convection region, once occurred in the height between 3 to 25km, and its maximum width was about 13km in radius.展开更多
基金This study was financially supported by the Joint Earthquake Science Foundation,CEA(A07058) .
文摘Recent fluid monitoring work shows that the contents of mantle-derived CO2, He and CH4 increased anomalously in 2002 and 2003. The ^3He/^4He ratio of the deep-fault-type Jinjiang hot springs increased highly anomalously in 2003, and then decreased in 2004. The ^3He/^4He ratio from the thermal-reservoir-type Changbaijulong hot springs increased slowly in 2003, and the increase continued in 2004. The mantle-derived He content of the He released from the Changbaijulong springs increased obviously in 2004. The anomaly of the released gases and the isotopic He was consistent with the trends of seismic activities in the Tianchi volcanic area between 2002 and 2004. The abnormal release of the Jinjiang hot springs apparently decreased after the seismic activities ceased in the second half of 2004, while the abnormal release from the Changbaljulong increased significantly after these seismic activities. It shows that the abnormal release of magmas-derived gases from the thermal-reservoir-type springs lags behind that of the deep-fault-type springs. These characteristics may be of great significance for identifying deep magmatic activity and predicting volcanic earthquakes in the future.
基金supported by the National Science Foundation of China(grant No.41472305)Special Project of China Earthquake Administration(grant No. 201108001)
文摘Objective The Tengchong volcanic field is situated along the southeastern margin of the Tibetan Plateau and adjacent to the border area of western Yunnan Province of China and Myanmar.Affected by the intense tectonic stress of subduction of the Indian plate to Eurasian plate,this volcanic field has experienced strong volcanism.
基金sponsored by the National Natural Foundation (40172033),China
文摘This paper deals with geochemical features of gas emitted from the Hubin Springs. The Hubin Springs zone, a strong thermal emission zone, is are locatedd at the north edge of the Tianchi caldera lake. Very young deposits with uncertain eruption date are found on the top area of the Tianwenfeng, which might have been formed in one of the recent eruptions or the Millennium Eruption. It is of significance to study the geochemistry features of the emitting gas from the Hubin Springs to understand the activities of the Tianchi Volcano. This paper systematically sampled and analyzed the gases emitted from the Hubin Springs and discussed their geochemistry features. The results show that there is a high content of deep derived gases, such as CO2, He, CH4 and Ar in Hubin Springs zone. The isotopic ratio of He lies between 4. 18 and 5. 95 Ra. The averaged mantle derived gas content calculated from the ^4He/2^20Ne ratio and He content reaches 67.1%. All these show that the Hubin Springs are located on a special belt of deep gases released in high intensity and large scale. The spatial distribution of Helium isotope is characterized by concavity, showing that this special area may be related to the volcanic edifice. It is highly possible that the released gases represent the residual gas samples of the latest eruptions from the Tianchi Volcano. However more detailed studies are demanded.
基金Sponsored by NSFC and the state volcano program 95 -11
文摘The huge comendite ignimbrite-forming eruption of Tianchi Volcano maintained a stable plinian column during its earlier stage of eruption, and succeeded a collapsing of the column producing pumiceous ignimbrite deposits. It is estimated that the column height (Hb) varied from 20km to 10km in its eruption period, with a maximum height of 25km in the eruption peak. Its umbrella cloud spread into the stratosphere with a top height of 35km (Ht). The dense lithics whose diameter exceeded 8cm followed a ballistics trajectory in a 3km-high gas thrust region, while the smaller lithics and pumices entered the convection region in the column. The initial magma temperature was 780℃. The comendite magma had an exit velocity of 300m/s, volatile content of about 1wt% and lithics of 8.5wt%. From a 400m-wide vent the magma was expelled out with a mass eruption rate of 108.36kg/s, corresponding to a volume rate of 104.95m 3/s. Over 1.3436×10 19 J of energy had been released from Tianchi Volcano, of which the kinetic proportion was about 8%. The plume had a temperature of -50℃ at the base focus of the cloud and a upward speed of 215m/s. The cloud spread out at a gradually downspeed with the increasement of distance from its center. For example, at a distance of 25km from its center the spreading velocity is about 250m/s, and is about 60m/s at distance of 100km. The main part of the plinian column, that is the convection region, once occurred in the height between 3 to 25km, and its maximum width was about 13km in radius.
