There occurred several eruptions from Changbaishan Tianchi volcano in Holocene,and at least three of them were believed to be true according to the formal studies.The products of three eruptions were yellow comenditic...There occurred several eruptions from Changbaishan Tianchi volcano in Holocene,and at least three of them were believed to be true according to the formal studies.The products of three eruptions were yellow comenditic pumice of～5000a B.P.(Eruption I),gray comenditic pumice and pyroclastic flow of～1000a B.P.(Eruption II,i.e.the millennium explosive eruption),black trachy pumice and welded tuff of～300a B.P.(Eruption Ⅲ)respectively.There were a large number of melt inclusions found in phenocrysts,which differ in size and color.The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of Changbaishan Tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ,whereas it was rather complicated for Eruption II,i.e.there might be two kinds of melt with different homogenization temperature periods,which gave the evidence for the assumption that the explosive millennium eruption of Tianchi volcano was triggered by injection and mixing of two different magmas.The experimental results also indicate that(1)small melt inclusion is easy to be homogenized,while the large one,especially the one with lots of daughter crystals,is rather difficult to be homogenized;(2)homogenization temperature closely correlates with the size of melt inclusion within host crystal,with the temperature point switching from high heating rate to low heating rate,and correlates with whether it is the first time to obtain homogenization as well;and(3)a melt inclusion can get different homogenization temperatures when it is repeatedly heated.Even more,the next homogenization temperature is usually higher than the former one,which testifies the phenomenon that hydrogen migration occurs during repeated heating.展开更多
High-frequency S-wave seismogram envelopes of microearthquakes broaden with increasing travel distance,a phenomenon known as S-wave envelope broadening. Multiple forward scattering and diffraction for the random inhom...High-frequency S-wave seismogram envelopes of microearthquakes broaden with increasing travel distance,a phenomenon known as S-wave envelope broadening. Multiple forward scattering and diffraction for the random inhomogeneities along the seismic ray path are the main causes of S-wave envelope broadening,so the phenomenon of S-wave envelope broadening is used to study the inhomogeneity of the medium. The peak delay time of an S-wave,which is defined as the time lag from the direct S-wave onset to the maximum amplitude arrival of its envelope,is accepted to quantify S-wave envelope broadening. 204 small earthquake records in Changbaishan Tianchi volcano were analyzed by the S-wave envelope broadening algorithm. The results show that S-wave envelope broadening in the Changbaishan Tianchi volcano is obvious,and that the peak delay time of S-wave has a positive correlation with the hypocenter distance and frequency of the S-wave. The relationships between the S-wave peak delay time and the hypocenter distance for different frequency bands were obtained using the statistics method. The results are beneficial to the understanding of the S-wave envelope broadening phenomena and the quantitative research on the inhomogeneities of the crust medium in the Changbaishan Tianchi volcano region.展开更多
In this paper, with the application of satellite thermal infrared remote sensing technique, nine land surface temperature distribution maps of Changbaishan Tianchi volcano area are retrieved from nine thermal infrared...In this paper, with the application of satellite thermal infrared remote sensing technique, nine land surface temperature distribution maps of Changbaishan Tianchi volcano area are retrieved from nine thermal infrared images which are taken from 1999 to 2008. In terms of NDVI (Normalized Difference Vegetation Index), we classify the surface cover of the study area into three types, i.e. vegetation (forest), mixture of soil and vegetation (short grasses), and bare rock. The average temperature of each type of surface covers is calculated first, and then the average daily temperature record from Tianchi meteorological station is subtracted in order to reduce the effect of weather variation. Finally, thermal anomalies of three types of surface cover in Changbaishan Tianchi vol-cano area in the period of 1999 to 2008 are obtained, which is believed to reflect the magmatic activity in the magma chamber under Tianchi volcano caldera. Our results indicate that temperature of the study area increased with an intermittent tendency during 1999 to 2005, but dropped after 2005, and then maintained a relatively stable state from 2006 to 2008. Such a tendency of annual temperature variation possibly caused by magmatic activity is correlated with the results observed by means of seismic monitoring, ground deformation from GPS measurement, and volcanic gas geochemistry monitoring in the same area. It is im-plied that the upward intrusion of magma may cause temperature increase, and such temperature variation is great enough so that could be detected by using satellite thermal infrared remote sensing technology.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
Recent fluid monitoring work shows that the contents of mantle-derived CO_2,He and CH_4 increased anomalously in 2002 and 2003. The 3He/4He ratio of the deep-fault-type Jinjiang hot springs increased highly anomalousl...Recent fluid monitoring work shows that the contents of mantle-derived CO_2,He and CH_4 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 Changbaijulong 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
The systematical 14 C age of a large gagatite, which has been found in the pumiceous airfall deposits of the last large eruption of Changbaishan\|Tianchi volcano, is dated from its centre to its edge. By fitting the 1...The systematical 14 C age of a large gagatite, which has been found in the pumiceous airfall deposits of the last large eruption of Changbaishan\|Tianchi volcano, is dated from its centre to its edge. By fitting the 14 C age with the high precise calibrated curve of tree ring, it is concluded that the date of the last large eruption is (1215±15)AD. In addition, the climatic effects of that large eruption are also discussed, pointing out that the last large eruption probably corresponds to the sulfuric acid peak at (1227±2)AD in GISP2 Greenland ice core.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
基金This research was jointly supported by basic scientific research project of Institute of Geology, CEA (DF-IGCEA-060719)National Natural Science Foundation of China(40672043)+1 种基金Science and Technology Tackling Project of CEA (2006BAC01B040104)China Scholarship Council,Ministry of Education
文摘There occurred several eruptions from Changbaishan Tianchi volcano in Holocene,and at least three of them were believed to be true according to the formal studies.The products of three eruptions were yellow comenditic pumice of～5000a B.P.(Eruption I),gray comenditic pumice and pyroclastic flow of～1000a B.P.(Eruption II,i.e.the millennium explosive eruption),black trachy pumice and welded tuff of～300a B.P.(Eruption Ⅲ)respectively.There were a large number of melt inclusions found in phenocrysts,which differ in size and color.The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of Changbaishan Tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ,whereas it was rather complicated for Eruption II,i.e.there might be two kinds of melt with different homogenization temperature periods,which gave the evidence for the assumption that the explosive millennium eruption of Tianchi volcano was triggered by injection and mixing of two different magmas.The experimental results also indicate that(1)small melt inclusion is easy to be homogenized,while the large one,especially the one with lots of daughter crystals,is rather difficult to be homogenized;(2)homogenization temperature closely correlates with the size of melt inclusion within host crystal,with the temperature point switching from high heating rate to low heating rate,and correlates with whether it is the first time to obtain homogenization as well;and(3)a melt inclusion can get different homogenization temperatures when it is repeatedly heated.Even more,the next homogenization temperature is usually higher than the former one,which testifies the phenomenon that hydrogen migration occurs during repeated heating.
基金sponsored by the National Key Technology R&D Program (2006BAC01B04)the Joint Earthquake Science Foundation (A08026,A07138),China
文摘High-frequency S-wave seismogram envelopes of microearthquakes broaden with increasing travel distance,a phenomenon known as S-wave envelope broadening. Multiple forward scattering and diffraction for the random inhomogeneities along the seismic ray path are the main causes of S-wave envelope broadening,so the phenomenon of S-wave envelope broadening is used to study the inhomogeneity of the medium. The peak delay time of an S-wave,which is defined as the time lag from the direct S-wave onset to the maximum amplitude arrival of its envelope,is accepted to quantify S-wave envelope broadening. 204 small earthquake records in Changbaishan Tianchi volcano were analyzed by the S-wave envelope broadening algorithm. The results show that S-wave envelope broadening in the Changbaishan Tianchi volcano is obvious,and that the peak delay time of S-wave has a positive correlation with the hypocenter distance and frequency of the S-wave. The relationships between the S-wave peak delay time and the hypocenter distance for different frequency bands were obtained using the statistics method. The results are beneficial to the understanding of the S-wave envelope broadening phenomena and the quantitative research on the inhomogeneities of the crust medium in the Changbaishan Tianchi volcano region.
基金supported by the National Natural Science Foundation of China (40972209)the National Key Technology R&D Program of China (2006BAC01B040102)
文摘In this paper, with the application of satellite thermal infrared remote sensing technique, nine land surface temperature distribution maps of Changbaishan Tianchi volcano area are retrieved from nine thermal infrared images which are taken from 1999 to 2008. In terms of NDVI (Normalized Difference Vegetation Index), we classify the surface cover of the study area into three types, i.e. vegetation (forest), mixture of soil and vegetation (short grasses), and bare rock. The average temperature of each type of surface covers is calculated first, and then the average daily temperature record from Tianchi meteorological station is subtracted in order to reduce the effect of weather variation. Finally, thermal anomalies of three types of surface cover in Changbaishan Tianchi vol-cano area in the period of 1999 to 2008 are obtained, which is believed to reflect the magmatic activity in the magma chamber under Tianchi volcano caldera. Our results indicate that temperature of the study area increased with an intermittent tendency during 1999 to 2005, but dropped after 2005, and then maintained a relatively stable state from 2006 to 2008. Such a tendency of annual temperature variation possibly caused by magmatic activity is correlated with the results observed by means of seismic monitoring, ground deformation from GPS measurement, and volcanic gas geochemistry monitoring in the same area. It is im-plied that the upward intrusion of magma may cause temperature increase, and such temperature variation is great enough so that could be detected by using satellite thermal infrared remote sensing technology.
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.
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 CO_2,He and CH_4 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 Changbaijulong 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The systematical 14 C age of a large gagatite, which has been found in the pumiceous airfall deposits of the last large eruption of Changbaishan\|Tianchi volcano, is dated from its centre to its edge. By fitting the 14 C age with the high precise calibrated curve of tree ring, it is concluded that the date of the last large eruption is (1215±15)AD. In addition, the climatic effects of that large eruption are also discussed, pointing out that the last large eruption probably corresponds to the sulfuric acid peak at (1227±2)AD in GISP2 Greenland ice core.
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.
