The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including...The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850＋ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth＇s deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the northcomponent azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.展开更多
Ureilites are a common group of achondrites with a high abundance of carbon. They probably have a genetic relationship with chondrites, hence provide an insight into origin and evdution of terrestrial planets. A new m...Ureilites are a common group of achondrites with a high abundance of carbon. They probably have a genetic relationship with chondrites, hence provide an insight into origin and evdution of terrestrial planets. A new meteorite-rich region, Grove Mountains （ GRV）, was found by the Chinese Antarctic Research Expedition, with discovery of 9834 meteorites. Of 2433 meteorites classified, 9 ureilites have been identified. In this paper, we report petrography of 6 of these ureilites. Four ureilites contain graphite and exhibit triangle conjunction and common reduced margins of divine. GRV 052382 probably experienced heavy shock metamorphism followed by fast coding, as indicated by mosaic texture or fine-grained granular texture of olivine. GRV 022931 was highly reduced of these ureilites, with olivine as isolated grains in abundant carbonaceous matrix. All 9 ureilites are monomict, and arc classified into subtype II （with medium FeO content, Fa15-18 ） and subtype I （with high FeO content, Fa 〉 18） based on compositions of the cores of olivine. The diverse mineral compositions and petrography of these ureilites suggest that they are not paired and reveal a multi-event history of the parent body. Partial melting of the parent body produced carbon-rich magma, followed by crystallization of graphite and silicates. Later, graphite was partially inverted to diamond by shock events. Reburial of the shocked debris experienced various degree of thermal metamorphism. Finally, these rocks were excavated from the parent asteroid and ejected into Earth-cross orbit by another impact event.展开更多
The study of Mg isotopes has been carried out for about 40 years since 1970 s. With analytical progress, the study is not only limited to the excess of ^26Mg due to decay of short-lived ^26Al in primitive meteorites, ...The study of Mg isotopes has been carried out for about 40 years since 1970 s. With analytical progress, the study is not only limited to the excess of ^26Mg due to decay of short-lived ^26Al in primitive meteorites, also extended to mass-dependent fractionation of Mg isotopes in meteorites and terrestrial rocks. This paper reviews recent development in Mg isotope researches.展开更多
This paper reviews and summarizes the Chinese Antarctica meteorite search, classification and research. During the past four antarctic explorations, a total of 9834 meteorites were collected in the Grove Mountains reg...This paper reviews and summarizes the Chinese Antarctica meteorite search, classification and research. During the past four antarctic explorations, a total of 9834 meteorites were collected in the Grove Mountains region. Among them, 2431 meteorites were classified by the end of 2008. So far, 684 meteorites have been officially published in the Meteoritical Bulletin, Meteoritical Society, including 2 martian meteorites, 2 eucrites, 6 ureilites, 5 mesosiderites, 1 pallasite, 1 iron and 10 carbonaceous chondrites. Comprehensive studies were carried out on a number of these rare type meteorites. In addition, we propose to continue the meteorite searching project in Grove Mountains and other regions in Antarctica. We also suggest several key topics of the future researches on the Chinese Antarctic meteorites.展开更多
The Pliocene fluvial/lacustrine sediments of the Sanying Formation lie along the Red River fault and its northwest extension;their majority outcrops appear around Eryuan.The Sanying Formation is characterized by multi...The Pliocene fluvial/lacustrine sediments of the Sanying Formation lie along the Red River fault and its northwest extension;their majority outcrops appear around Eryuan.The Sanying Formation is characterized by multiple intercalated coal layers and its unconformities contact with the underlying Triassic limestone and the overlying Quaternary coarse sediments.Cosmogenic nuclide burial dating confirms the Pliocene age of the Sanying Formation.The burial ages of the overlying Quaternary sediments provide the lower age limit of the Sanying Formation:2 Ma.Detrital zircon U-Pb age distribution suggests provenance of the Sanying Formation traced to the Songpan-Ganzi flysch belt.From the spatial distribution as well as sedimentary and fault ages,we found a strong connection of the Sanying Formation with the Red River and the Jianchuan faults.We therefore propose that activation of the Red River and the Jianchuan faults during the Late Miocene resulted in subsidence of basins in the extensional areas around Eryuan and in the middle to south segments of the Red River fault.The basins were filled with water carried by the Jinsha River and overflow-lakes formed within the basins where the Sanying Formation was deposited.Most of the lakes were dried and sedimentation of the Sanying Formation ceased due to the uplift of the Yunling Mountains,which forced rerouting of the Jinsha River at the beginning of Quaternary.展开更多
We analyzed teleseismic waveforms recorded by 36 stations near Bohai Sea region and obtained 2 248 high quality receiver functions.The crustal thickness (H) and average crustal vP/vS ratio (κ) as well as the Poisson&...We analyzed teleseismic waveforms recorded by 36 stations near Bohai Sea region and obtained 2 248 high quality receiver functions.The crustal thickness (H) and average crustal vP/vS ratio (κ) as well as the Poisson's ratios beneath 34 stations were estimated using the H-κ stacking method.The results indicate that crustal thicknesses near the Liaoning province range from 30.0 to 35.5 km,and the corresponding vP/vS ratios vary from 1.72 to 1.89 which corresponds to Poisson's ratio with a range from 0.243 to 0.305.We also apply a common conversion point (CCP) stacking method of receiver function (RF) to image the upper mantle discontinuity structure beneath Bohai Sea region.Both the 410-km and the 660-km discontinuities (hereafter called the 410 and the 660) show clearly in the study region.The transition zone (TZ) thickness shows a different picture from the west to the east of the study region,which is a little bit thicker than that of the global average in the west of longitude 122°E,however,thinner in the east of longitude 122°E.We suggested that the dehydration of sinking slab into the lower mantle or a small-scale mantle plume from the lower mantle generated hot upwelling beneath this region.展开更多
It has been debated whether there was southward movement of the South China Block （SCB） during the Cretaceous. In this study, a paleomagnetic investigation was carried out on the Late Cretaceous volcanic rocks （-88...It has been debated whether there was southward movement of the South China Block （SCB） during the Cretaceous. In this study, a paleomagnetic investigation was carried out on the Late Cretaceous volcanic rocks （-88 Ma） of the Shimaoshan Group in Yongtai County, Fujian Province. Rock magnetic experiments showed that magnetite in pseudo-single-domain and multi-domain grain and hematite were predominant magnetic phases. Stepwise thermal demagnetization successfully isolated characteristic directional components at high-temperature interval （〉 500℃） from 383 specimens in 19 sites, which yielded a paleomagnetic pole for the studied section at 83.1°N, 152.6°E （N = 19, A95 = 3.9°）, and the scatter SB = 9.0. The Fisher distri- bution of virtual geomagnetic poles （VGPs） and the consistence of S8 with the expected value at the 95% confidence level in- dicate that the yielded paleomagnetic pole is free of paleomagnetic secular variation influence. The new pole, which is well consistent with that from the Eurasian apparent polar wander path （APWP） curve, suggests no obvious southward movement of the sampling site during the Cretaceous.展开更多
The magnetic properties of magnetosome magnetite are of interdisciplinary interest because magnetosomes are potential carriers of natural remanent magnetization and paleoenvironment, as well as novel nano-biomaterials...The magnetic properties of magnetosome magnetite are of interdisciplinary interest because magnetosomes are potential carriers of natural remanent magnetization and paleoenvironment, as well as novel nano-biomaterials in biotechnological and biomedical applications. We carried out magnetic and electron transmission microscopy analyses of fresh Magnetospirillum magneticum AMB-1 whole cells and isolated magnetosomes. Results revealed that AMB-1 synthesized single-domain magnetite magneto-somes, which are arranged in the form of linear fragmental chain. The distinct differences of magnetic properties between these two samples can be faithfully interpreted in terms of spatial arrangement of magnetosomes and magnetostatic interaction. For the whole cells, the strong intra-chain interactions and weak inter-chain interactions generate behaviors of non-interacting uniaxial single-domain particles. Its δ-ratio is 3.0 and passes the Moskowitz test. In contrast, the isolated magnetosome sample has reduced values of coercivity and δ-ratio (1.5), due to increasing three-dimensional magnetostatic interactions and collapse of magneto-some chains. These observations provide useful insights into applications of the biogenic magnetite (magnetosomes) in magnetic nano-materials and magnetofossils in the paleomagnetic and environmental magnetism.展开更多
Y984028 is a new lherzolitic shergottite,consisting of poikilitic and non-poikilitic lithologies.The mafic silicates are FeO-poor,and the chromite is TiO 2-poor in the poikilitic lithology compared to the grains in th...Y984028 is a new lherzolitic shergottite,consisting of poikilitic and non-poikilitic lithologies.The mafic silicates are FeO-poor,and the chromite is TiO 2-poor in the poikilitic lithology compared to the grains in the non-poikilitic lithology.This meteorite shares similarmineral petrography andmineral chemistry with GRV 99027,but is not paired with the latter because of their different shock-induced features.Y984028 was severely shocked and experienced no significant thermal metamorphism after the main impact event.Hence,Y984028 serves as a probe for the study of meteorite impact processes on terrestrial surfaces.The melt veins in Y984028 are characterized by the absence of any high-pressure polymorphs,the presence of abundant smallmineral fragments,and the prevailing granulation textures of olivine and chromite.These features are consistent with adiabatic melting during the release of shock-induced high-pressure and quenching at ambient pressure.展开更多
基金supported by NSF grant EAR-063566(F.N.)National Natural Science Foundation of China grant 40774042(J.L.)
文摘The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850＋ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth＇s deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the northcomponent azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.
基金supported by the National Natural Science Foundation of China(No.40473037 and 40673055)Guangxi College Talents Support Program(RC2007020)
文摘Ureilites are a common group of achondrites with a high abundance of carbon. They probably have a genetic relationship with chondrites, hence provide an insight into origin and evdution of terrestrial planets. A new meteorite-rich region, Grove Mountains （ GRV）, was found by the Chinese Antarctic Research Expedition, with discovery of 9834 meteorites. Of 2433 meteorites classified, 9 ureilites have been identified. In this paper, we report petrography of 6 of these ureilites. Four ureilites contain graphite and exhibit triangle conjunction and common reduced margins of divine. GRV 052382 probably experienced heavy shock metamorphism followed by fast coding, as indicated by mosaic texture or fine-grained granular texture of olivine. GRV 022931 was highly reduced of these ureilites, with olivine as isolated grains in abundant carbonaceous matrix. All 9 ureilites are monomict, and arc classified into subtype II （with medium FeO content, Fa15-18 ） and subtype I （with high FeO content, Fa 〉 18） based on compositions of the cores of olivine. The diverse mineral compositions and petrography of these ureilites suggest that they are not paired and reveal a multi-event history of the parent body. Partial melting of the parent body produced carbon-rich magma, followed by crystallization of graphite and silicates. Later, graphite was partially inverted to diamond by shock events. Reburial of the shocked debris experienced various degree of thermal metamorphism. Finally, these rocks were excavated from the parent asteroid and ejected into Earth-cross orbit by another impact event.
基金supported by the Pilot Project of Knowledge Innovation Program of the Chinese Academy of Sciences(kzcx2-yw-Q08)the Natural Science Foundation of China(Grants 40873054)
文摘The study of Mg isotopes has been carried out for about 40 years since 1970 s. With analytical progress, the study is not only limited to the excess of ^26Mg due to decay of short-lived ^26Al in primitive meteorites, also extended to mass-dependent fractionation of Mg isotopes in meteorites and terrestrial rocks. This paper reviews recent development in Mg isotope researches.
基金supported by the Knowledge Innovation Programof the Chinese Academy of Sciences(kzcx2-yw-110,KZCX2-YW-Q08)
文摘This paper reviews and summarizes the Chinese Antarctica meteorite search, classification and research. During the past four antarctic explorations, a total of 9834 meteorites were collected in the Grove Mountains region. Among them, 2431 meteorites were classified by the end of 2008. So far, 684 meteorites have been officially published in the Meteoritical Bulletin, Meteoritical Society, including 2 martian meteorites, 2 eucrites, 6 ureilites, 5 mesosiderites, 1 pallasite, 1 iron and 10 carbonaceous chondrites. Comprehensive studies were carried out on a number of these rare type meteorites. In addition, we propose to continue the meteorite searching project in Grove Mountains and other regions in Antarctica. We also suggest several key topics of the future researches on the Chinese Antarctic meteorites.
基金supported by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant No.XDB03020300)National Natural Science Foundation of China(Grant Nos.41173067&41021063)
文摘The Pliocene fluvial/lacustrine sediments of the Sanying Formation lie along the Red River fault and its northwest extension;their majority outcrops appear around Eryuan.The Sanying Formation is characterized by multiple intercalated coal layers and its unconformities contact with the underlying Triassic limestone and the overlying Quaternary coarse sediments.Cosmogenic nuclide burial dating confirms the Pliocene age of the Sanying Formation.The burial ages of the overlying Quaternary sediments provide the lower age limit of the Sanying Formation:2 Ma.Detrital zircon U-Pb age distribution suggests provenance of the Sanying Formation traced to the Songpan-Ganzi flysch belt.From the spatial distribution as well as sedimentary and fault ages,we found a strong connection of the Sanying Formation with the Red River and the Jianchuan faults.We therefore propose that activation of the Red River and the Jianchuan faults during the Late Miocene resulted in subsidence of basins in the extensional areas around Eryuan and in the middle to south segments of the Red River fault.The basins were filled with water carried by the Jinsha River and overflow-lakes formed within the basins where the Sanying Formation was deposited.Most of the lakes were dried and sedimentation of the Sanying Formation ceased due to the uplift of the Yunling Mountains,which forced rerouting of the Jinsha River at the beginning of Quaternary.
基金supported by the National Natural Science Foundation of China grants 40674028 and 40474022
文摘We analyzed teleseismic waveforms recorded by 36 stations near Bohai Sea region and obtained 2 248 high quality receiver functions.The crustal thickness (H) and average crustal vP/vS ratio (κ) as well as the Poisson's ratios beneath 34 stations were estimated using the H-κ stacking method.The results indicate that crustal thicknesses near the Liaoning province range from 30.0 to 35.5 km,and the corresponding vP/vS ratios vary from 1.72 to 1.89 which corresponds to Poisson's ratio with a range from 0.243 to 0.305.We also apply a common conversion point (CCP) stacking method of receiver function (RF) to image the upper mantle discontinuity structure beneath Bohai Sea region.Both the 410-km and the 660-km discontinuities (hereafter called the 410 and the 660) show clearly in the study region.The transition zone (TZ) thickness shows a different picture from the west to the east of the study region,which is a little bit thicker than that of the global average in the west of longitude 122°E,however,thinner in the east of longitude 122°E.We suggested that the dehydration of sinking slab into the lower mantle or a small-scale mantle plume from the lower mantle generated hot upwelling beneath this region.
基金supported by National Natural Science Foundation of China (Grant Nos. 40634024 and40821091)
文摘It has been debated whether there was southward movement of the South China Block （SCB） during the Cretaceous. In this study, a paleomagnetic investigation was carried out on the Late Cretaceous volcanic rocks （-88 Ma） of the Shimaoshan Group in Yongtai County, Fujian Province. Rock magnetic experiments showed that magnetite in pseudo-single-domain and multi-domain grain and hematite were predominant magnetic phases. Stepwise thermal demagnetization successfully isolated characteristic directional components at high-temperature interval （〉 500℃） from 383 specimens in 19 sites, which yielded a paleomagnetic pole for the studied section at 83.1°N, 152.6°E （N = 19, A95 = 3.9°）, and the scatter SB = 9.0. The Fisher distri- bution of virtual geomagnetic poles （VGPs） and the consistence of S8 with the expected value at the 95% confidence level in- dicate that the yielded paleomagnetic pole is free of paleomagnetic secular variation influence. The new pole, which is well consistent with that from the Eurasian apparent polar wander path （APWP） curve, suggests no obvious southward movement of the sampling site during the Cretaceous.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40821091 and 40325011)Hundred Talents Program of the Chi-nese Academy of Sciences and Marie-Curie Fellowship (IIF) Return Phase of (Grant No. MIF1-CT-2005-007555)
文摘The magnetic properties of magnetosome magnetite are of interdisciplinary interest because magnetosomes are potential carriers of natural remanent magnetization and paleoenvironment, as well as novel nano-biomaterials in biotechnological and biomedical applications. We carried out magnetic and electron transmission microscopy analyses of fresh Magnetospirillum magneticum AMB-1 whole cells and isolated magnetosomes. Results revealed that AMB-1 synthesized single-domain magnetite magneto-somes, which are arranged in the form of linear fragmental chain. The distinct differences of magnetic properties between these two samples can be faithfully interpreted in terms of spatial arrangement of magnetosomes and magnetostatic interaction. For the whole cells, the strong intra-chain interactions and weak inter-chain interactions generate behaviors of non-interacting uniaxial single-domain particles. Its δ-ratio is 3.0 and passes the Moskowitz test. In contrast, the isolated magnetosome sample has reduced values of coercivity and δ-ratio (1.5), due to increasing three-dimensional magnetostatic interactions and collapse of magneto-some chains. These observations provide useful insights into applications of the biogenic magnetite (magnetosomes) in magnetic nano-materials and magnetofossils in the paleomagnetic and environmental magnetism.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-110 and KZCX2-YW-Q08)
文摘Y984028 is a new lherzolitic shergottite,consisting of poikilitic and non-poikilitic lithologies.The mafic silicates are FeO-poor,and the chromite is TiO 2-poor in the poikilitic lithology compared to the grains in the non-poikilitic lithology.This meteorite shares similarmineral petrography andmineral chemistry with GRV 99027,but is not paired with the latter because of their different shock-induced features.Y984028 was severely shocked and experienced no significant thermal metamorphism after the main impact event.Hence,Y984028 serves as a probe for the study of meteorite impact processes on terrestrial surfaces.The melt veins in Y984028 are characterized by the absence of any high-pressure polymorphs,the presence of abundant smallmineral fragments,and the prevailing granulation textures of olivine and chromite.These features are consistent with adiabatic melting during the release of shock-induced high-pressure and quenching at ambient pressure.
