At 21:45 hr (Beijing time ) on Oct. 31, 1990 the Yanzhuang meteorite hit the ground atthe Yanzhuang village, Wenyuan County, Guangdong Province. Several fragments, tota1ling 3. 5 kg,were recovered during the field sur...At 21:45 hr (Beijing time ) on Oct. 31, 1990 the Yanzhuang meteorite hit the ground atthe Yanzhuang village, Wenyuan County, Guangdong Province. Several fragments, tota1ling 3. 5 kg,were recovered during the field survey. This meteorite is a rare one of its kind due to its heavilyshocked features and thick veins made up of black molten materials.olivine and lowcalcium pyroxene are compositionally homogeneous with Fa= 18. 59, Fs= 16. 35and Wo = 1. 29. The chemica1 composition (total Fe=28. 0% ) and recrystallized texture of thechondritic mass show that the Yanzhuang is an H6 chondrite. The black molten materials occur inthe form of blocks (up to 2×3×4 cm in size) and veins (0.1 - 15 mm in width), and contain a lotof rounded and elliptic FeNi-FeS blobs (up to 6- 10 mm in length). The metal in these blobs exhib-its distinct dendritic str-ucture characteristic of rapid cooling. Unmolten and molten samples are verysimilar in chemical composition, fitting well with the average H-chondrites. Partial melting andFeNi/FeS-silicate separation have not been observed in the molten materials of the Yanzhuang.展开更多
Relatively old ages of chondrites(normally around 4.5Ga)suggest that their parent bodies did not experience any mely-fractionation under high temperature and high pressure conditions pertaining to the interior of terr...Relatively old ages of chondrites(normally around 4.5Ga)suggest that their parent bodies did not experience any mely-fractionation under high temperature and high pressure conditions pertaining to the interior of terrestrial plaets.Therefore,it is reasonable to take chondrites as starting materials in the study of the chemical evolution of the early earth.The sillicate phase in the Jilin chondrite (H5)was chosen for this purpose because it possesses a chemical composition similar to that of the primitive mantle.The melting experiment was carried out at 20-30 k bar and has rsulted in a product which contains1-5% melts in addition to solid cryustal phase.The chemical composition of the melt phases and the partitioning of various elements between the coexisting silicate melts are geochemically similar to those of anatectic rocks on the earth.This can thus serve as the basis for discussing the chemical evolution of the early upper mantle.展开更多
Metal grains in stony meteorites are relatively movable during thermal netamorphism(Wood,1967;Xie and Wang,1979;Xie,1986).In view of the fact that the Jilin meteorite is the largest in the world known up to now,its ma...Metal grains in stony meteorites are relatively movable during thermal netamorphism(Wood,1967;Xie and Wang,1979;Xie,1986).In view of the fact that the Jilin meteorite is the largest in the world known up to now,its main body weighing 1770kg and its total volume amounting to 117×93×84cm^3,a de-tailed investigation into such a huge meteorite body would undoubtedly provide us with a lot of clues and information valuable in the study of the behavior of Fe-Ni metal during thermal metamorphism of meteorites.Our recent investigation has revealed that during thermal metamorphism of the Jilin chondirte fine Fe-Ni metal particles migrated easily by diffusion in solid state,and subsequently aggregated into metal nodules about 5-10mm in length,and the largest nodule we found is 30mm in size (Photo1).In this paper we present some new results of our study concerning the migra-tion and concentration of Fe-Ni metal in the Jilin chondrite on the basis of op-tical,SEM observations and high-temperature-high pressure as well as shock loading experiments.展开更多
Instrumental neutron activation analysis(INAA) of 14 single oldhamite grains separated from the Qingzhen chondrite (EH3) for refractory(La,Ce,Sm ,Eu,Yb,Lu,Ca,Sc,Hf, and Th),volatile (Na,Cr,Zn,Se,Br,etc.)and siderophil...Instrumental neutron activation analysis(INAA) of 14 single oldhamite grains separated from the Qingzhen chondrite (EH3) for refractory(La,Ce,Sm ,Eu,Yb,Lu,Ca,Sc,Hf, and Th),volatile (Na,Cr,Zn,Se,Br,etc.)and siderophile elements (Fe,Ni,Co,Ir,Au ,and As) revealed that oldhamite is highly rich in refractory elements.The mineral serves as the principal carrier of REE and contains about 80% of the REEs in the Qingzhen enstatite chondrite .Furthermore, the large enrichment of LREE relative to HREE is noticed in oldhamite from the Qingzhen .In general, the oldhamite from metal-sulfide assemblages is richer in REE than that from the matrix,i.e.,the earlier the oldhamite grains condensed, the richer they are in REE. Meanwhile.oldhamite is also rich in vol-atile elements such as Se,Br, etc.In terms of the distribution of trace elements in oldhamitc from the Qingzhen ,the chondrite is srggested to have resulted from high-temperature condensation of solar nebula.展开更多
This paper deals with the effects of thermal and collision events which had been experienced by the Jilin(H5) and Qingzhen(EH3) chondrites before they fell to the earth .The HRTEM and opti-cal microscopic investigatio...This paper deals with the effects of thermal and collision events which had been experienced by the Jilin(H5) and Qingzhen(EH3) chondrites before they fell to the earth .The HRTEM and opti-cal microscopic investigations show that the Jilin chondrite has undergone more extensive thermal heating and two stages of collision,while the Qingzhen chondrite has experienced weak thermal events after the accretion of its parent body and one stage of moderate collision.The schematic dia-grams of the process of formation and evolution of these two meteorites are given in the present pa-per.展开更多
The data available show that some Antarctic caboaceous chondrites are similar toCl meteorites. They contain a lot of phyllorilicate aggregates and the oxygen isotopic composition of the whole-rock samples is approxima...The data available show that some Antarctic caboaceous chondrites are similar toCl meteorites. They contain a lot of phyllorilicate aggregates and the oxygen isotopic composition of the whole-rock samples is approximate to that of Cl chondrites, so they are named afterquasi-Cl (Q-Cl ) chondrites. Unlike Cl metoorites, the Q-Cl chondrites possess chondrulestructure, and the compositions of high-temperature condensates (chondrule fragments, mineral grains or aggregates) show that the oxygen fugacity varied within a wide range in the surroundings where they were formed, similar to the variation range from E-, H-, L-, LL- t0 C-group chondrites. It is inferred that the Q-Cl chondrites could be formed at the edges far fromthe equator in the whole asteroid region of the soar nebular disk, where the nebula was lowerin density and the txindensates were lower in accretion velocity, so that the hydration of chondrules and matrix occurred during the late stage of nebular condensation. The discovery of theQ-Cl chondrites and the fact that the earth and other terrestrial planets contain water indicatethat at the edges far from the erluator in the terrestrial region of the solar nebular disk, a largeamount of water was incorporated into the lattice of minerals in the condensates as a result ofhydration during nebular condensation, and then found its way into the interior parts of theEarth and other terrestrial planets due to accretion.展开更多
Polarization and radiation measurements and microwave studies show that the planets and the great majority of asteroids in the solar system are covered by soils similar to regolith on the moon surface.The soils repese...Polarization and radiation measurements and microwave studies show that the planets and the great majority of asteroids in the solar system are covered by soils similar to regolith on the moon surface.The soils repesent the composition of the asteroids and the geological elements of the planets. The spectral reflectance shows a tendency of decreasing from near ultraviolet,visible to near-infrared in order of LL→L→H→H with increasing Fe^0/Fet rato and toward to absorption for Jilin,Xinyang and Zanoyang ordinary chondrites and Qinzhen enstatite chondrite recently fallen in China,The same chemical group of meteorites feature deeper absorption valleys with increasing metamorphic grade.The spectal reflectance of igneous rocks varies from strong to what is like that of H-group chondrites in order of acid→basic→ultrabasic rocks.展开更多
Six Chinese ordinary chondrites (four of them have fallen in recent years and the trace element abundances have not yet been reported for the other two) were examined.The contents of 21 elements (Na,Cr,Mn,Sc,Se,Zn,Br,...Six Chinese ordinary chondrites (four of them have fallen in recent years and the trace element abundances have not yet been reported for the other two) were examined.The contents of 21 elements (Na,Cr,Mn,Sc,Se,Zn,Br,Ni,Fe,Co,Ir,Cu,Ga,As,Au,Sb,Os,W,Re,Pt,and Ru)in the magnetic fractions and 20 elements (Na,K,Ca,Sc,Cr,Mn,Fe,Co,Ni,Zn,Se,Br,La,Sm,Eu,Yb,Lu,Ir,Au,and As) in the non-magnetic fractions were de-termined by INAA. The results indicate that the 5 H-group chondrites show almost no difference in composition,but they are different from the Zhaodong L-group chondrite in elemental abundance.As a normalized element(relative to CI),the concentrations of Ga in the magnetic fractions can be used to classify ordinary chondrites(H-,L- and LL-group).The bulk composition and modal weight of each component calculated from element concentrations in different phases are in good agreement with the bulk rock analyses presented in the literature.展开更多
Stable isotopic data of meteorites are critical for understanding the evolution of terrestrial planets. In this study, we report high-precision vanadium （V） isotopic compositions of 11 unequilibrated and equilibrate...Stable isotopic data of meteorites are critical for understanding the evolution of terrestrial planets. In this study, we report high-precision vanadium （V） isotopic compositions of 11 unequilibrated and equilibrated L chondrites. Our samples show an average δ^51v of -1.25‰ ±0.38‰ （2SD, n = 11）, which is ,- 0.5‰ lighter than that of the bulk silicate Earth constrained by mantle peridotites. Isotopic fractionation in type 3 ordinary chondrites vary from - 1.76‰ to - 1.29‰, whereas the δ^51V of equilibrated chondrites vary from - 1.37‰ to -1.08‰. 551V of L chondrites do not correlate with thermal metamorphism, shock stage, or weathering degree. Future studies are required to explore the reason for V isotope variation in the solar system.展开更多
文摘At 21:45 hr (Beijing time ) on Oct. 31, 1990 the Yanzhuang meteorite hit the ground atthe Yanzhuang village, Wenyuan County, Guangdong Province. Several fragments, tota1ling 3. 5 kg,were recovered during the field survey. This meteorite is a rare one of its kind due to its heavilyshocked features and thick veins made up of black molten materials.olivine and lowcalcium pyroxene are compositionally homogeneous with Fa= 18. 59, Fs= 16. 35and Wo = 1. 29. The chemica1 composition (total Fe=28. 0% ) and recrystallized texture of thechondritic mass show that the Yanzhuang is an H6 chondrite. The black molten materials occur inthe form of blocks (up to 2×3×4 cm in size) and veins (0.1 - 15 mm in width), and contain a lotof rounded and elliptic FeNi-FeS blobs (up to 6- 10 mm in length). The metal in these blobs exhib-its distinct dendritic str-ucture characteristic of rapid cooling. Unmolten and molten samples are verysimilar in chemical composition, fitting well with the average H-chondrites. Partial melting andFeNi/FeS-silicate separation have not been observed in the molten materials of the Yanzhuang.
基金This project was supported by the China National Scientific Foundation.
文摘Relatively old ages of chondrites(normally around 4.5Ga)suggest that their parent bodies did not experience any mely-fractionation under high temperature and high pressure conditions pertaining to the interior of terrestrial plaets.Therefore,it is reasonable to take chondrites as starting materials in the study of the chemical evolution of the early earth.The sillicate phase in the Jilin chondrite (H5)was chosen for this purpose because it possesses a chemical composition similar to that of the primitive mantle.The melting experiment was carried out at 20-30 k bar and has rsulted in a product which contains1-5% melts in addition to solid cryustal phase.The chemical composition of the melt phases and the partitioning of various elements between the coexisting silicate melts are geochemically similar to those of anatectic rocks on the earth.This can thus serve as the basis for discussing the chemical evolution of the early upper mantle.
文摘Metal grains in stony meteorites are relatively movable during thermal netamorphism(Wood,1967;Xie and Wang,1979;Xie,1986).In view of the fact that the Jilin meteorite is the largest in the world known up to now,its main body weighing 1770kg and its total volume amounting to 117×93×84cm^3,a de-tailed investigation into such a huge meteorite body would undoubtedly provide us with a lot of clues and information valuable in the study of the behavior of Fe-Ni metal during thermal metamorphism of meteorites.Our recent investigation has revealed that during thermal metamorphism of the Jilin chondirte fine Fe-Ni metal particles migrated easily by diffusion in solid state,and subsequently aggregated into metal nodules about 5-10mm in length,and the largest nodule we found is 30mm in size (Photo1).In this paper we present some new results of our study concerning the migra-tion and concentration of Fe-Ni metal in the Jilin chondrite on the basis of op-tical,SEM observations and high-temperature-high pressure as well as shock loading experiments.
基金This project was financially supported by the National Natural Science Foundation of China.
文摘Instrumental neutron activation analysis(INAA) of 14 single oldhamite grains separated from the Qingzhen chondrite (EH3) for refractory(La,Ce,Sm ,Eu,Yb,Lu,Ca,Sc,Hf, and Th),volatile (Na,Cr,Zn,Se,Br,etc.)and siderophile elements (Fe,Ni,Co,Ir,Au ,and As) revealed that oldhamite is highly rich in refractory elements.The mineral serves as the principal carrier of REE and contains about 80% of the REEs in the Qingzhen enstatite chondrite .Furthermore, the large enrichment of LREE relative to HREE is noticed in oldhamite from the Qingzhen .In general, the oldhamite from metal-sulfide assemblages is richer in REE than that from the matrix,i.e.,the earlier the oldhamite grains condensed, the richer they are in REE. Meanwhile.oldhamite is also rich in vol-atile elements such as Se,Br, etc.In terms of the distribution of trace elements in oldhamitc from the Qingzhen ,the chondrite is srggested to have resulted from high-temperature condensation of solar nebula.
文摘This paper deals with the effects of thermal and collision events which had been experienced by the Jilin(H5) and Qingzhen(EH3) chondrites before they fell to the earth .The HRTEM and opti-cal microscopic investigations show that the Jilin chondrite has undergone more extensive thermal heating and two stages of collision,while the Qingzhen chondrite has experienced weak thermal events after the accretion of its parent body and one stage of moderate collision.The schematic dia-grams of the process of formation and evolution of these two meteorites are given in the present pa-per.
文摘The data available show that some Antarctic caboaceous chondrites are similar toCl meteorites. They contain a lot of phyllorilicate aggregates and the oxygen isotopic composition of the whole-rock samples is approximate to that of Cl chondrites, so they are named afterquasi-Cl (Q-Cl ) chondrites. Unlike Cl metoorites, the Q-Cl chondrites possess chondrulestructure, and the compositions of high-temperature condensates (chondrule fragments, mineral grains or aggregates) show that the oxygen fugacity varied within a wide range in the surroundings where they were formed, similar to the variation range from E-, H-, L-, LL- t0 C-group chondrites. It is inferred that the Q-Cl chondrites could be formed at the edges far fromthe equator in the whole asteroid region of the soar nebular disk, where the nebula was lowerin density and the txindensates were lower in accretion velocity, so that the hydration of chondrules and matrix occurred during the late stage of nebular condensation. The discovery of theQ-Cl chondrites and the fact that the earth and other terrestrial planets contain water indicatethat at the edges far from the erluator in the terrestrial region of the solar nebular disk, a largeamount of water was incorporated into the lattice of minerals in the condensates as a result ofhydration during nebular condensation, and then found its way into the interior parts of theEarth and other terrestrial planets due to accretion.
文摘Polarization and radiation measurements and microwave studies show that the planets and the great majority of asteroids in the solar system are covered by soils similar to regolith on the moon surface.The soils repesent the composition of the asteroids and the geological elements of the planets. The spectral reflectance shows a tendency of decreasing from near ultraviolet,visible to near-infrared in order of LL→L→H→H with increasing Fe^0/Fet rato and toward to absorption for Jilin,Xinyang and Zanoyang ordinary chondrites and Qinzhen enstatite chondrite recently fallen in China,The same chemical group of meteorites feature deeper absorption valleys with increasing metamorphic grade.The spectal reflectance of igneous rocks varies from strong to what is like that of H-group chondrites in order of acid→basic→ultrabasic rocks.
文摘Six Chinese ordinary chondrites (four of them have fallen in recent years and the trace element abundances have not yet been reported for the other two) were examined.The contents of 21 elements (Na,Cr,Mn,Sc,Se,Zn,Br,Ni,Fe,Co,Ir,Cu,Ga,As,Au,Sb,Os,W,Re,Pt,and Ru)in the magnetic fractions and 20 elements (Na,K,Ca,Sc,Cr,Mn,Fe,Co,Ni,Zn,Se,Br,La,Sm,Eu,Yb,Lu,Ir,Au,and As) in the non-magnetic fractions were de-termined by INAA. The results indicate that the 5 H-group chondrites show almost no difference in composition,but they are different from the Zhaodong L-group chondrite in elemental abundance.As a normalized element(relative to CI),the concentrations of Ga in the magnetic fractions can be used to classify ordinary chondrites(H-,L- and LL-group).The bulk composition and modal weight of each component calculated from element concentrations in different phases are in good agreement with the bulk rock analyses presented in the literature.
基金financially supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB18000000)the National Science Foundation of China (41173077, 41776196, 41630206, and 41325011)+1 种基金the National Science and Technology Foundation Platform Project of Ministry of Science and Technology of China (2005DKA21406)the 111 Project
文摘Stable isotopic data of meteorites are critical for understanding the evolution of terrestrial planets. In this study, we report high-precision vanadium （V） isotopic compositions of 11 unequilibrated and equilibrated L chondrites. Our samples show an average δ^51v of -1.25‰ ±0.38‰ （2SD, n = 11）, which is ,- 0.5‰ lighter than that of the bulk silicate Earth constrained by mantle peridotites. Isotopic fractionation in type 3 ordinary chondrites vary from - 1.76‰ to - 1.29‰, whereas the δ^51V of equilibrated chondrites vary from - 1.37‰ to -1.08‰. 551V of L chondrites do not correlate with thermal metamorphism, shock stage, or weathering degree. Future studies are required to explore the reason for V isotope variation in the solar system.
