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 Tianchi volcano in the Changbai Mountains is located on the boundary between China and North Korea.There are many times of eruptions of the Tianchi volcano during the Holocene.One of its large eruptions occurred a...The Tianchi volcano in the Changbai Mountains is located on the boundary between China and North Korea.There are many times of eruptions of the Tianchi volcano during the Holocene.One of its large eruptions occurred around 1000 years ago dated by ^(14)C method and historical records.Composition of products of the largest Tianchi volcanic eruption studied is characterized by comendi-tic Plinian fallout and unwelded ignimbrite,which are mainly distributed in China and North Korea.Caldera is about 4.4 km long and 3.4 km wide,which had filled with water(e.g.Tianchi Lake).The Tianchi volcanic cone is about 2700 m high above sea level.The Tianchi Lake is located on the summit of the volcanic cone,that is also highest peak of the Changbai Mountains in northeastern China.This study analyzed Cl,F,S and H_(2)O concentrations of melt inclusions in the phenocryst min-erals(anorthoclase and quartz)and co-existing matrix glasses using the electron microprobe and estimated environmental effect of Tianchi volcanic gases.The authors proposed a new method to evaluate future eruption of active volcano and estimate potential volcanic hazards based on contents of volatile emissions.Using this method,we made a perspective of future volcanic hazard in this region.展开更多
On the basis of the chemical components and stable isotopic compositions of escaped gases from the Tianchi volcanic geothermal area, the material sources of these gases are discussed, presenting that they are mainly d...On the basis of the chemical components and stable isotopic compositions of escaped gases from the Tianchi volcanic geothermal area, the material sources of these gases are discussed, presenting that they are mainly derived from the residual mantle-derived magma in the crust; Changbai geothermal area may be directly interlinked with the eruption canal in history; there is a stable reservoir of the geothermal water and the deep-seated gases under the Changbai geothermal area, with water temperature of the reservoir being about (166±9)℃.展开更多
In this paper, we describe three strata at the distal part of the pyroclastic-flow from the Tianchi volcano in 1215 （±15） eruption. One of the strata with crosslayers that are different from typical pyroclastic...In this paper, we describe three strata at the distal part of the pyroclastic-flow from the Tianchi volcano in 1215 （±15） eruption. One of the strata with crosslayers that are different from typical pyroclastic-flow strata may come from a ground-surge. The grain-size and scanning electron microscopy （SEM） analysis was performed to study the origin of the pyroclastic-flow. Characteristics of grain-size distribution show that it is similar with the ash cloud. Through the SEM analyses, we found some quench structures with less damage on the surfaces of the vitric pumices. These phenomena indicate that there has been hydration in the transportation processes at the distal of pyroclastic-flow. It has partly changed the transportation mechanism of pyroclastic-flow, which transitions form dense flow to diluted flow. This paper develops a new distal pyroclastic-flow model in the Tianchi volcano that can be divided into three stages, i.e. the quench stage, expanding stage and depositing stage.展开更多
Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation.The Tianchi Bogda Peak Natural Reserve(TBPNR),located in Xinjiang Uygur Autonomous Region,China,i...Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation.The Tianchi Bogda Peak Natural Reserve(TBPNR),located in Xinjiang Uygur Autonomous Region,China,is an important ecological barrier area in the temperate arid zone.The evaluation of its important ecosystem services is of great significance to improve the management level and ecological protection efficiency of the reserve.In the present study,we assessed the spatiotemporal variations of four ecosystem services(including net primary productivity(NPP),water yield,soil conservation,and habitat quality)in the TBPNR from 2000 to 2020 based on the environmental and social data using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.In addition,the coldspot and hotspot areas of ecosystem services were identified by hotspot analysis,and the trade-off and synergistic relationships between ecosystem services were analyzed using factor analysis in a geographic detector.During the study period,NPP and soil conservation values in the reserve increased by 48.20%and 25.56%,respectively;conversely,water yield decreased by 16.56%,and there was no significant change in habitat quality.Spatially,both NPP and habitat quality values were higher in the northern part and lower in the southern part,whereas water yield showed an opposite trend.Correlation analysis revealed that NPP showed a synergistic relationship with habitat quality and soil conservation,and exhibited a trade-off relationship with water yield.Water yield and habitat quality also had a trade-off relationship.NPP and habitat quality were affected by annual average temperature and Normalized Difference Vegetation Index(NDVI),respectively,while water yield and soil conservation were more affected by digital elevation model(DEM).Therefore,attention should be paid to the spatial distribution and dynamics of trade-off and synergistic relationships between ecosystem services in future ecological management.The findings of the present 展开更多
The impact of tourist disturbance on the environment has become a focal issue of environmental science, ecology, and travel management studies. To assess the influence of tourist disturbance on soils and plants in the...The impact of tourist disturbance on the environment has become a focal issue of environmental science, ecology, and travel management studies. To assess the influence of tourist disturbance on soils and plants in the Tianchi scenic area of Xinjiang, China, we compared soil properties and plant community characteristics at 0, 5, 10, and 20 m from the tourist trail within areas at three different altitudes, where the intensities of tourist disturbance are distinct. Surface water quality was also studied at three different levels relative to the Tianchi Lake. The results showed that tourist disturbance significantly increased soil pH within 10 m from the trail and soil bulk density on the edge of the trail, but significantly reduced soil organic matter and total nitrogen contents within 5 m from the trail. The number of tree seedlings on the edge of the trail and the shrub coverage and height of herbaceous plants within 5 m from the trail significantly decreased due to tourist disturbance. Changes in herbaceous plant diversity differed by soil zones. In the high altitude region, tourist disturbance led to a remarkable increase in the herbaceous plant diversity on the edge of the trail, while in the low altitude region, tourist disturbance had a low impact on the diversity of herbaceous plants. In addition, tourist activities polluted the surface water, significantly reducing water quality. Thus, current tourist activities have a significant negative impact on the ecological environment in the Tianchi scenic area.展开更多
As an important approach for relieving conflicts between ecosystems and human activities in the Tianchi Scenic Area, Xinjiang of China, an ecological migration policy was implemented, aiming to improve the regional ec...As an important approach for relieving conflicts between ecosystems and human activities in the Tianchi Scenic Area, Xinjiang of China, an ecological migration policy was implemented, aiming to improve the regional ecological environment. The case of resettlement was closely related to the smooth implementation of the migration project. Based on the questionnaires and farmer family interviews, both changes in the ecological environment and the living conditions of migrant farmer families in the Tianchi Scenic Area were investigated in this study. The objectives were to assess the benefits of the ecological migration policy and to analyze the effects of ecological migration on migrant farmer families. The results showed that （1） awareness of the need for ecological environmental protection and the types of migrant families had a great influence on the willingness to migration; （2） since the implementation of the ecological migration project, the ecological environment in the Tianchi Scenic Area had improved significantly, particutarly in terms of returning farmland to forestry, while pressures on grassland had also been relieved to some extent; （3） the major income sources and occupations of the migrant farmer families changed, the range of their income sources declined, and their per capita incomes decreased at different degrees; and （4） nearly half of the farmer families were not satisfied with the living environment of new settlements and the decline in the quality of life had significant influences on the attitudes of migrants. In order to ensure the successful implementation of an ecological migration project, it is essential to enhance farmer awareness of needs for ecological environmental protection, and to solve resettlement problems properly.展开更多
The Changbaishan Tianchi volcano is composed of the basaltic rocks at the shield-forming stage, the trachyte and pantellerite at the cone-forming stage and modern eruption. Studies on their REE, incompatible elements ...The Changbaishan Tianchi volcano is composed of the basaltic rocks at the shield-forming stage, the trachyte and pantellerite at the cone-forming stage and modern eruption. Studies on their REE, incompatible elements and Sr, Nd, Pb isotopes suggest that rocks at different stages have a common magma genesis and close evolution relationship with differentiation crystallization playing the key role. The co-eruption of basaltic trachyandesite magma and pantellerite magma indicates that there exist both crustal magma chamber and mantle magma reservoir beneath the Tianchi volcano.展开更多
We report the oxide,element geochemistry and Nd isotopic geochemical data of apatite in the middle Pleistocene medium-and fine-grained trachyte in the Tianchi volcanic area(TVA)of Changbai Mountain,discussing the rela...We report the oxide,element geochemistry and Nd isotopic geochemical data of apatite in the middle Pleistocene medium-and fine-grained trachyte in the Tianchi volcanic area(TVA)of Changbai Mountain,discussing the relationship between apatite and the composition of the whole rock.The purpose is to use the apatite geochemical data to constrain the evolutionary process of trachytic magma and the petrogenesis of trachyte in the cone-forming period of the Tianchi volcano.Apatite(Ca_(5)(PO_(4))_(3)(OH,F,Cl))is a common accessory mineral that occurs widely in volcanic rocks in the TVA.The apatites in the trachyte are mainly subhedral-anhedral,having the characteristics of magmatic apatite.In terms of oxide and element geochemistry,they have homogeneous Al_(2)O_(3),SiO_(2),MgO,P_(2)O_(5),K_(2)O,CaO and heterogeneous TiO2,with high F content.They are generally enriched in Th,U and LREEs,depleted in Nb,Ta,Zr,Hf and HFSEs,showing negative Ba,Sr and Ti anomalies,similar to those of the whole-rock host trachytes.The ratios of high(La/Yb)_(N),low δEu(Eu/Eu*),Sr/Y value and ΣREE content in apatite,and the F,Sr,Y,Th/U,La/Sm,and Nd/Tb with ΣREE andδEu anomalies showed a linear correlation,all of those indicating that the host magma has the characteristic of high differentiation.The apatite grains generally having ^(147)Sm/^(144)Nd,^(143)Nd/^(144)Nd ratios and ε_(Nd)(t)values of 0.1072-0.1195,0.5123-0.5126 and -3.49 to -0.10,respectively,are similiar to those of the host rock.The Nd model ages TDM1 are 949-803 Ma in apatite.Combined with theεNd(t)value of the apatite core(-7.06 to-3.49),we conclude that the initial magma of the host trachyte was derived from the partial melting of Proterozoic crustal material and there was an assimilation of wall rocks during its evolution.展开更多
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
TIANCHI volcano,Changbaishan Mountains isthe largest modern active volcano in East Chi-na.Many times strong volcanic erupting activ-ities occurred in the Cenozoic Era.The vol-canic activities have revived again in the...TIANCHI volcano,Changbaishan Mountains isthe largest modern active volcano in East Chi-na.Many times strong volcanic erupting activ-ities occurred in the Cenozoic Era.The vol-canic activities have revived again in the Re-cent.Field investigation results show thatthere are a lot of hydrothermal anomaly out-展开更多
Volcanic eruption is an important external forcing factor of climate change on time scale from month to hundred years.In this paper,the climatic effect of the last large historical eruption of Tianchi volcano,which ha...Volcanic eruption is an important external forcing factor of climate change on time scale from month to hundred years.In this paper,the climatic effect of the last large historical eruption of Tianchi volcano,which happened in 1229 AD,has been investigated with a two-dimensional energy balance model.Taking Mt.Pinatubo volcano and Changbai Mountain-Tianchi volcano for example,the numerical simulation on time scale from months to years indicates that such large eruptions may have significant impacts on global climate.Based on the simulation results,it is suggested that the last large eruption of Tianchi volcano should be responsible for the abrupt climate change event,which began in the period from 1230 to 1260 AD.展开更多
Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave along the profile L1 are determined simultaneously with deep seismic sounding data in Changbai...Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave along the profile L1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson's ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method, and it is also very effective to determine Poisson's ratio distribution of deep seismic sounding profile, especially useful for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson's ratio body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson's ratio is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature. There is a high Poisson's ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot substance. The lower part with high Poisson's ratio, which stretches downward to Moho, is possibly the extrusion way of hot substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination of 3D crustal structure and magnetotelluric survey in this region.展开更多
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supported by the National Natural Science Foundation of China(Grant No.40372045)the Chinese Academy of Sciences(Grant No.KZCX3-SW-145)the Chinese Academy of Sciences(Grant No.KZCX3-SW-145).
文摘The Tianchi volcano in the Changbai Mountains is located on the boundary between China and North Korea.There are many times of eruptions of the Tianchi volcano during the Holocene.One of its large eruptions occurred around 1000 years ago dated by ^(14)C method and historical records.Composition of products of the largest Tianchi volcanic eruption studied is characterized by comendi-tic Plinian fallout and unwelded ignimbrite,which are mainly distributed in China and North Korea.Caldera is about 4.4 km long and 3.4 km wide,which had filled with water(e.g.Tianchi Lake).The Tianchi volcanic cone is about 2700 m high above sea level.The Tianchi Lake is located on the summit of the volcanic cone,that is also highest peak of the Changbai Mountains in northeastern China.This study analyzed Cl,F,S and H_(2)O concentrations of melt inclusions in the phenocryst min-erals(anorthoclase and quartz)and co-existing matrix glasses using the electron microprobe and estimated environmental effect of Tianchi volcanic gases.The authors proposed a new method to evaluate future eruption of active volcano and estimate potential volcanic hazards based on contents of volatile emissions.Using this method,we made a perspective of future volcanic hazard in this region.
基金Project supported by the National Natural Science Foundation of China
文摘On the basis of the chemical components and stable isotopic compositions of escaped gases from the Tianchi volcanic geothermal area, the material sources of these gases are discussed, presenting that they are mainly derived from the residual mantle-derived magma in the crust; Changbai geothermal area may be directly interlinked with the eruption canal in history; there is a stable reservoir of the geothermal water and the deep-seated gases under the Changbai geothermal area, with water temperature of the reservoir being about (166±9)℃.
基金supported by the National Science Foundation Project(Grant No.40972209)Special Fund of State Public Institute for Basic Research(Grant No.IGCEA 1101)
文摘In this paper, we describe three strata at the distal part of the pyroclastic-flow from the Tianchi volcano in 1215 （±15） eruption. One of the strata with crosslayers that are different from typical pyroclastic-flow strata may come from a ground-surge. The grain-size and scanning electron microscopy （SEM） analysis was performed to study the origin of the pyroclastic-flow. Characteristics of grain-size distribution show that it is similar with the ash cloud. Through the SEM analyses, we found some quench structures with less damage on the surfaces of the vitric pumices. These phenomena indicate that there has been hydration in the transportation processes at the distal of pyroclastic-flow. It has partly changed the transportation mechanism of pyroclastic-flow, which transitions form dense flow to diluted flow. This paper develops a new distal pyroclastic-flow model in the Tianchi volcano that can be divided into three stages, i.e. the quench stage, expanding stage and depositing stage.
基金This research was funded by the Key Laboratory for Sustainable Development of Xinjiang's Historical and Cultural Tourism,Xinjiang University,China(LY2022-06)the Tianchi Talent Project.
文摘Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation.The Tianchi Bogda Peak Natural Reserve(TBPNR),located in Xinjiang Uygur Autonomous Region,China,is an important ecological barrier area in the temperate arid zone.The evaluation of its important ecosystem services is of great significance to improve the management level and ecological protection efficiency of the reserve.In the present study,we assessed the spatiotemporal variations of four ecosystem services(including net primary productivity(NPP),water yield,soil conservation,and habitat quality)in the TBPNR from 2000 to 2020 based on the environmental and social data using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.In addition,the coldspot and hotspot areas of ecosystem services were identified by hotspot analysis,and the trade-off and synergistic relationships between ecosystem services were analyzed using factor analysis in a geographic detector.During the study period,NPP and soil conservation values in the reserve increased by 48.20%and 25.56%,respectively;conversely,water yield decreased by 16.56%,and there was no significant change in habitat quality.Spatially,both NPP and habitat quality values were higher in the northern part and lower in the southern part,whereas water yield showed an opposite trend.Correlation analysis revealed that NPP showed a synergistic relationship with habitat quality and soil conservation,and exhibited a trade-off relationship with water yield.Water yield and habitat quality also had a trade-off relationship.NPP and habitat quality were affected by annual average temperature and Normalized Difference Vegetation Index(NDVI),respectively,while water yield and soil conservation were more affected by digital elevation model(DEM).Therefore,attention should be paid to the spatial distribution and dynamics of trade-off and synergistic relationships between ecosystem services in future ecological management.The findings of the present
基金sponsored by the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists(2015VEA048)the National Natural Science Foundation of China(41301163+2 种基金41301204)the Project of Featured Major Tourism Management(HHXY2013LY)the Doctoral Startup Funds from Huanghuai University(2013D1310)
文摘The impact of tourist disturbance on the environment has become a focal issue of environmental science, ecology, and travel management studies. To assess the influence of tourist disturbance on soils and plants in the Tianchi scenic area of Xinjiang, China, we compared soil properties and plant community characteristics at 0, 5, 10, and 20 m from the tourist trail within areas at three different altitudes, where the intensities of tourist disturbance are distinct. Surface water quality was also studied at three different levels relative to the Tianchi Lake. The results showed that tourist disturbance significantly increased soil pH within 10 m from the trail and soil bulk density on the edge of the trail, but significantly reduced soil organic matter and total nitrogen contents within 5 m from the trail. The number of tree seedlings on the edge of the trail and the shrub coverage and height of herbaceous plants within 5 m from the trail significantly decreased due to tourist disturbance. Changes in herbaceous plant diversity differed by soil zones. In the high altitude region, tourist disturbance led to a remarkable increase in the herbaceous plant diversity on the edge of the trail, while in the low altitude region, tourist disturbance had a low impact on the diversity of herbaceous plants. In addition, tourist activities polluted the surface water, significantly reducing water quality. Thus, current tourist activities have a significant negative impact on the ecological environment in the Tianchi scenic area.
基金funded by the National Natural Science Foundation of China (40801065)the Dr.Western-funded projects of Chinese Academy of Sciences (XBBS 200803)
文摘As an important approach for relieving conflicts between ecosystems and human activities in the Tianchi Scenic Area, Xinjiang of China, an ecological migration policy was implemented, aiming to improve the regional ecological environment. The case of resettlement was closely related to the smooth implementation of the migration project. Based on the questionnaires and farmer family interviews, both changes in the ecological environment and the living conditions of migrant farmer families in the Tianchi Scenic Area were investigated in this study. The objectives were to assess the benefits of the ecological migration policy and to analyze the effects of ecological migration on migrant farmer families. The results showed that （1） awareness of the need for ecological environmental protection and the types of migrant families had a great influence on the willingness to migration; （2） since the implementation of the ecological migration project, the ecological environment in the Tianchi Scenic Area had improved significantly, particutarly in terms of returning farmland to forestry, while pressures on grassland had also been relieved to some extent; （3） the major income sources and occupations of the migrant farmer families changed, the range of their income sources declined, and their per capita incomes decreased at different degrees; and （4） nearly half of the farmer families were not satisfied with the living environment of new settlements and the decline in the quality of life had significant influences on the attitudes of migrants. In order to ensure the successful implementation of an ecological migration project, it is essential to enhance farmer awareness of needs for ecological environmental protection, and to solve resettlement problems properly.
文摘The Changbaishan Tianchi volcano is composed of the basaltic rocks at the shield-forming stage, the trachyte and pantellerite at the cone-forming stage and modern eruption. Studies on their REE, incompatible elements and Sr, Nd, Pb isotopes suggest that rocks at different stages have a common magma genesis and close evolution relationship with differentiation crystallization playing the key role. The co-eruption of basaltic trachyandesite magma and pantellerite magma indicates that there exist both crustal magma chamber and mantle magma reservoir beneath the Tianchi volcano.
基金funded by research on the strategy of Improving the All-for-one Tourism Transportation Capacity of Changbai Mountain and the China Scholarship Council(Grant Nos.JL2021-03 and 202104190014)。
文摘We report the oxide,element geochemistry and Nd isotopic geochemical data of apatite in the middle Pleistocene medium-and fine-grained trachyte in the Tianchi volcanic area(TVA)of Changbai Mountain,discussing the relationship between apatite and the composition of the whole rock.The purpose is to use the apatite geochemical data to constrain the evolutionary process of trachytic magma and the petrogenesis of trachyte in the cone-forming period of the Tianchi volcano.Apatite(Ca_(5)(PO_(4))_(3)(OH,F,Cl))is a common accessory mineral that occurs widely in volcanic rocks in the TVA.The apatites in the trachyte are mainly subhedral-anhedral,having the characteristics of magmatic apatite.In terms of oxide and element geochemistry,they have homogeneous Al_(2)O_(3),SiO_(2),MgO,P_(2)O_(5),K_(2)O,CaO and heterogeneous TiO2,with high F content.They are generally enriched in Th,U and LREEs,depleted in Nb,Ta,Zr,Hf and HFSEs,showing negative Ba,Sr and Ti anomalies,similar to those of the whole-rock host trachytes.The ratios of high(La/Yb)_(N),low δEu(Eu/Eu*),Sr/Y value and ΣREE content in apatite,and the F,Sr,Y,Th/U,La/Sm,and Nd/Tb with ΣREE andδEu anomalies showed a linear correlation,all of those indicating that the host magma has the characteristic of high differentiation.The apatite grains generally having ^(147)Sm/^(144)Nd,^(143)Nd/^(144)Nd ratios and ε_(Nd)(t)values of 0.1072-0.1195,0.5123-0.5126 and -3.49 to -0.10,respectively,are similiar to those of the host rock.The Nd model ages TDM1 are 949-803 Ma in apatite.Combined with theεNd(t)value of the apatite core(-7.06 to-3.49),we conclude that the initial magma of the host trachyte was derived from the partial melting of Proterozoic crustal material and there was an assimilation of wall rocks during its evolution.
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.
文摘TIANCHI volcano,Changbaishan Mountains isthe largest modern active volcano in East Chi-na.Many times strong volcanic erupting activ-ities occurred in the Cenozoic Era.The vol-canic activities have revived again in the Re-cent.Field investigation results show thatthere are a lot of hydrothermal anomaly out-
文摘Volcanic eruption is an important external forcing factor of climate change on time scale from month to hundred years.In this paper,the climatic effect of the last large historical eruption of Tianchi volcano,which happened in 1229 AD,has been investigated with a two-dimensional energy balance model.Taking Mt.Pinatubo volcano and Changbai Mountain-Tianchi volcano for example,the numerical simulation on time scale from months to years indicates that such large eruptions may have significant impacts on global climate.Based on the simulation results,it is suggested that the last large eruption of Tianchi volcano should be responsible for the abrupt climate change event,which began in the period from 1230 to 1260 AD.
基金Key Project from China Earthquake Administration and the Project (95-11-02-01) from Ministry of Science and Technology (2001DIA10003).
文摘Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave along the profile L1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson's ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method, and it is also very effective to determine Poisson's ratio distribution of deep seismic sounding profile, especially useful for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson's ratio body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson's ratio is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature. There is a high Poisson's ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot substance. The lower part with high Poisson's ratio, which stretches downward to Moho, is possibly the extrusion way of hot substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination of 3D crustal structure and magnetotelluric survey in this region.
