Magnetic excitations for Ba isotopes are discussed within the nucleon-pair shell model truncated in the SD subspace. With the SD pair determined by a surface- interaction, M1 transitions for are well fitted. The M1 a...Magnetic excitations for Ba isotopes are discussed within the nucleon-pair shell model truncated in the SD subspace. With the SD pair determined by a surface- interaction, M1 transitions for are well fitted. The M1 and M3 transitions for and are also predicted. It is shown that the statement, the collective magnetic properties are due to the orbital motion of nucleons, is approximately valid.展开更多
Emeishan large igneous province (ELIP),one of the largest continental volcanic provinces worldwide (e.g.,Karoo),is extensively distributed along the western margin of the Yangtze Block.Even though the consensus that t...Emeishan large igneous province (ELIP),one of the largest continental volcanic provinces worldwide (e.g.,Karoo),is extensively distributed along the western margin of the Yangtze Block.Even though the consensus that the ELIP is of a plume-related origin has been reached for decades,the role of crustal contamination in the petrogenesis of these basalts is still debatable so far.This paper firstly reports the Ba isotopic compositions of the continental flood basalts from the Lijiang,Miyi and Emeishan regions to discuss the genesis of basalts from the ELIP.According to their TiO_(2) contents and Ti/Y ratios,these basalts are divided into two groups,the low-Ti basalts from Lijiang and the high-Ti basalts from Miyi and Emeishan.The Ba isotopic compositions show that the low-Ti basalts have the δ^(138/134)Ba values from-0.33‰to+0.23‰with an average of-0.02‰±0.40‰,and the high-Ti basalts from -0.38‰to+0.38‰with an average of 0.038‰±0.36‰,all of which show a wider range of Ba isotopes relative to that of the primitive mantle (PM).This is unlikely to be explained by partial melting,fractional crystallization or even chemical weathering owing to little Ba isotopic fractionation during these processes.In contrast,variable extents of crustal contamination into the basaltic magmas more likely resulted in such isotopic diversity.The ratios of incompatible elements (e.g.,Nb/U,La/Nb,and Nb/Y) further suggest that the low-Ti basalts experienced higher degrees of crustal contaminations than those high-Ti basalts,which is well consistent with their spatial distributions.In general,the basaltic magmas in the ELIP were probably contaminated by different degrees of crustal materials during their upwelling to the surface.展开更多
Chemical weathering of rocks and minerals alters the geochemical compositions of the lithosphere,hydrosphere,and atmosphere over time,regulating Earth’s surface temperature by consuming atmospheric CO_(2) so as to su...Chemical weathering of rocks and minerals alters the geochemical compositions of the lithosphere,hydrosphere,and atmosphere over time,regulating Earth’s surface temperature by consuming atmospheric CO_(2) so as to sustain our habitable planet.As the most mobile species in the processes of chemical weathering,cations are thought to be robust geochemical tracers of chemical weathering.Over the past decades,numerous tracers have been proposed for monitoring chemical weathering,mainly focusing on the contents and ratios of cations.Because of the difference from the properties of cations,information that they provide on chemical weathering over different timescales can be inconsistent or even false,such that some avenues of research have reached an impasse.By virtue of the identical properties of isotopes of the same element and the high-dimensional information that they carry,the stable isotopes of cations have been employed to objectively trace chemical weathering processes,which has become a rapidly developing direction of chemical weathering research.In this review,we summarize the progress made in tracing chemical weathering via the stable cation isotopes(δ^(7) Li,δ^(26) Mg,δ^(41) K,δ^(44/40) Ca,δ^(87/85) Rb,δ^(88/86) Sr,and δ^(138/134) Ba)and point out the development trends and persisting problems.After considering the virtues and deficiencies of various cation isotopes,we recommend the combination of multiple cation isotopes that complement and support one another as the future direction to obtain the reliable information on each process of chemical weathering.This should provide the most effective method for objectively tracing chemical weathering,thereby deepening our understanding of the regulatory mechanisms influencing the habitable surficial temperature.展开更多
文摘Magnetic excitations for Ba isotopes are discussed within the nucleon-pair shell model truncated in the SD subspace. With the SD pair determined by a surface- interaction, M1 transitions for are well fitted. The M1 and M3 transitions for and are also predicted. It is shown that the statement, the collective magnetic properties are due to the orbital motion of nucleons, is approximately valid.
基金financially supported by the Program of Co-construction and Development of Universities(No.8000019z050201)。
文摘Emeishan large igneous province (ELIP),one of the largest continental volcanic provinces worldwide (e.g.,Karoo),is extensively distributed along the western margin of the Yangtze Block.Even though the consensus that the ELIP is of a plume-related origin has been reached for decades,the role of crustal contamination in the petrogenesis of these basalts is still debatable so far.This paper firstly reports the Ba isotopic compositions of the continental flood basalts from the Lijiang,Miyi and Emeishan regions to discuss the genesis of basalts from the ELIP.According to their TiO_(2) contents and Ti/Y ratios,these basalts are divided into two groups,the low-Ti basalts from Lijiang and the high-Ti basalts from Miyi and Emeishan.The Ba isotopic compositions show that the low-Ti basalts have the δ^(138/134)Ba values from-0.33‰to+0.23‰with an average of-0.02‰±0.40‰,and the high-Ti basalts from -0.38‰to+0.38‰with an average of 0.038‰±0.36‰,all of which show a wider range of Ba isotopes relative to that of the primitive mantle (PM).This is unlikely to be explained by partial melting,fractional crystallization or even chemical weathering owing to little Ba isotopic fractionation during these processes.In contrast,variable extents of crustal contamination into the basaltic magmas more likely resulted in such isotopic diversity.The ratios of incompatible elements (e.g.,Nb/U,La/Nb,and Nb/Y) further suggest that the low-Ti basalts experienced higher degrees of crustal contaminations than those high-Ti basalts,which is well consistent with their spatial distributions.In general,the basaltic magmas in the ELIP were probably contaminated by different degrees of crustal materials during their upwelling to the surface.
基金supported by the National Natural Science Foundation of China(42221003,41930864,42103055,42373054)the National Key Research and Development Program of China(2022YFF0800101).
文摘Chemical weathering of rocks and minerals alters the geochemical compositions of the lithosphere,hydrosphere,and atmosphere over time,regulating Earth’s surface temperature by consuming atmospheric CO_(2) so as to sustain our habitable planet.As the most mobile species in the processes of chemical weathering,cations are thought to be robust geochemical tracers of chemical weathering.Over the past decades,numerous tracers have been proposed for monitoring chemical weathering,mainly focusing on the contents and ratios of cations.Because of the difference from the properties of cations,information that they provide on chemical weathering over different timescales can be inconsistent or even false,such that some avenues of research have reached an impasse.By virtue of the identical properties of isotopes of the same element and the high-dimensional information that they carry,the stable isotopes of cations have been employed to objectively trace chemical weathering processes,which has become a rapidly developing direction of chemical weathering research.In this review,we summarize the progress made in tracing chemical weathering via the stable cation isotopes(δ^(7) Li,δ^(26) Mg,δ^(41) K,δ^(44/40) Ca,δ^(87/85) Rb,δ^(88/86) Sr,and δ^(138/134) Ba)and point out the development trends and persisting problems.After considering the virtues and deficiencies of various cation isotopes,we recommend the combination of multiple cation isotopes that complement and support one another as the future direction to obtain the reliable information on each process of chemical weathering.This should provide the most effective method for objectively tracing chemical weathering,thereby deepening our understanding of the regulatory mechanisms influencing the habitable surficial temperature.
