Extraterrestrial dust exhibits a wide range of textural,chemical and oxygen isotopic compositions due to the heterogeneity of their precursors and modification during atmospheric entry.Experimental heating provides an...Extraterrestrial dust exhibits a wide range of textural,chemical and oxygen isotopic compositions due to the heterogeneity of their precursors and modification during atmospheric entry.Experimental heating provides an opportunity to investigate the relationship between thermal processing and micrometeorite composition for a known precursor material.We conducted experiments to simulate the atmospheric entry of micrometeorites(MMs)using controlled,short-duration(10-50 s)flash heating(400-1600℃)of CI chondrite chips(<1500µm)in atmospheric air(1 bar,21%O2)combined with microanalysis(textures,chemical and isotopic compositions)of the experimental products.The heated chips closely resemble natural samples,with materials similar to unmelted MMs,partially melted(scoriaceous)MMs and fully melted cosmic spherules produced.We reproduced several key features such as dehydration cracks,magnetite rims,volatile gas release,vesicle formation and coalescence,melting and quench cooling.Our parameter space allows for discriminating peak temperature and heating duration effects.Peak temperature is the first-order control on MM mineralogy,while heating duration controls vesicle coalescence and homogenization.When compared against previous heating experiments,our data demonstrates that CI chondrite dust is more thermally resistant,relative to CM chondrite dust,by approximately+200℃.The 207 measurement of O-isotopes allows,for the first time,petrographic effects(such as volatile degassing and melting)to be correlated against bulk O-isotope evolution.Our results demonstrate findings applicable to CI chondrites and potentially to all fine-grained hydrated carbonaceous chondrite dust grains:(1)O-isotope variations arising during sub-solidus heating are dominated by the release of water from phyllosilicates,forcing the residual MM composition towards its anhydrous precursor composition.(2)Oxygen isotope compositions undergo the most significant changes at supra-solidus temperatures.As previously demonstrated and now empirically confirmed,most of these changes are driven by a mass-dependent fractionation effect caused by evaporation,which shifts residual rock compositions toward heavier values.Mixing with atmospheric air alters compositions toward the terrestrial fractionation line.Notably,these two processes do not begin simultaneously.Our data indicate that at 1200℃,isotopic evolution is dominated by evaporative mass loss.However,at higher temperatures(1400-1600℃),both pronounced evaporation and mixing with atmospheric oxygen become active,resulting in a more complex isotopic signature.(3)The total change in Δ17O during heating up to 1600℃is<3‰and in most scenarios<2‰.展开更多
NWA 16080 is a representative reduced CV carbonaceous chondrite(CV_(red)),consisting mainly of chon-drules(47 vol%)and matrix(42 vol%),along with minor quantities of calcium-and aluminum-rich inclusions(CAI)and amoebo...NWA 16080 is a representative reduced CV carbonaceous chondrite(CV_(red)),consisting mainly of chon-drules(47 vol%)and matrix(42 vol%),along with minor quantities of calcium-and aluminum-rich inclusions(CAI)and amoeboid olivine aggregates(AOA)(CAI+AOA,6 vol%)and opaque minerals(5 vol%).The chondrules exhibit well-preserved outlines and can be categorized into Type Ⅰ(Fa<10)and Type Ⅱ(Fa>10).They primarily consist of magnesium-rich olivine,along with both low-Ca and high-Ca pyroxenes,and contain minor amounts of secondary plagioclase.Olivines present in chondrules display compositional zoning characterized whereas the matrix is composed of fine-grained olivine.Nickel-rich metal and nickel-poor sulfides are also present,along with trace amounts of magnetite.In contrast to standard oxidized CV chondrites(CV_(ox)),the presence of high metal,Ni-poor sulfides,and reduced magnetite in NWA 16080 indicates a more reduced parent-body environment.Shock metamorphism is classified as mild(S1),while terrestrial weathering is characterized as low(W2).Raman spectroscopy indicates a diverse spectrum of organic matter(OM)maturity:certain areas exhibit characteristics akin to other CV_(red) chondrites,whereas others reach maturity levels comparable to those observed in CV_(ox) chondrites.The Raman parameters indicate that this meteorite is classified as approximately type 3.4 to 3.5.The overlapping OM maturity with certain CV_(ox) chondrites provides a contradiction to the anticipated depth-thermal layering outlined in the onion-shell model.This suggests that the CV parent body probably experienced more intricate processes,including impacts and fluid-rock interactions,rather than merely depth-dependent heating.展开更多
Copper possesses very strong chacophile properties,but under the conditions found in meteorites,its behavior is like that of siderophile elements.The Suizhou meteorite is a highly shocked L6 chondrite.Troilite and tae...Copper possesses very strong chacophile properties,but under the conditions found in meteorites,its behavior is like that of siderophile elements.The Suizhou meteorite is a highly shocked L6 chondrite.Troilite and taenite are considered the main primary carrier of copper in this meteorite,and the post-shock thermal episode is considered the main reason that elemental Cu migrates from its original host phase and forms metallic grains.The Suizhou meteorite contains a few very thin shock melt veins.The occurrence and behavior of metallic copper in this meteorite were studied by optical microscopic examination,electron microprobe analyses,and high-resolution X-ray elemental intensity mapping.Our results show that metallic copper is abundant in the Suizhou chondritic rock.Metallic copper grains adjacent to small troilite grains inside FeNi metal are the most common occurrence,and those at the FeNi metal–troilite interface are the second most common case.The metallic copper grains occurring at the interface of FeNi metal/troililte and silicate are rather rare.Metallic copper grains are not observed within the Suizhou shock veins,Instead,Cu in elemental form is transferred through shock metamorphism into FeNi metal+troilite intergrowths.Four diff erent occurrence types of Cu in the FeNi metal+troilite intergrowths have been identifi ed:the concentrations of Cu in the FeNi+FeS intergrowths for four occurrence types are rather close,we estimate it might be lower than 1 wt%.展开更多
The mineralogy and petrography of EET 14017 were studied using optical microscope,scanning electron microscope,electron microprobe,and micro-Raman.The mineral chemistry of olivine,pyroxene,plagioclase,spinel,and Fe-Ni...The mineralogy and petrography of EET 14017 were studied using optical microscope,scanning electron microscope,electron microprobe,and micro-Raman.The mineral chemistry of olivine,pyroxene,plagioclase,spinel,and Fe-Ni metal in EET 14017 is comparable to that of previously studied L/LL3.0x chondrites.In particular,the Cr2O3 content in the ferroan chondrule olivine and the excess silica component,[]Si4O8,in the plagioclase lead us to conclude that EET 14017 belongs to subtype 3.05.Raman spectral data of carbonaceous matter from the matrix of EET 14017 suggest a higher degree of thermal metamorphism,probably due to terrestrial weathering in Antarctica.EET 14017 and some of the other L/LL3.0x chondrites from the EET region are possibly a pair,since they have similar Cr2O3 contents of ferroan chondrule olivines and Raman spectral data,and moreover they were also found in a restricted region of the blue ice field.The plagioclase in some chondrules is a late crystal phase in the chondrule melt,which may constrain the timing of chondrule formation and cooling rate.If more L/LL3.0x chondrites like EET 14017 from Antarctica are identified,they would be excellent source material for studying the early evolution of the Solar System.展开更多
The shock metamorphism of 47 H group chondrites （H-chondrites） from the Grove Mountains including undulatory extinction, planar fractures, mosaic extinction, shock veins and pockets, and dendritic eutectic metal-sul...The shock metamorphism of 47 H group chondrites （H-chondrites） from the Grove Mountains including undulatory extinction, planar fractures, mosaic extinction, shock veins and pockets, and dendritic eutectic metal-sulfide, is observed through optical microscope. The textures and assemblages of shock veins in these H-chondrites are examined by the scanning electron microscope. Based on observations of the above shock effects, the shock stages of the 47 H-chondrites are classified into S1（5）, S2（19）,S$3（14）, S4（8） and S5（1）. Of these H-chondrites, GRV 022469 has the highest（S5） shock stage. The comparison of shock stages in these H-chondrites with L group chondrites（L-chondrites） indicates that the shock metamorphism of H-chondrites is relatively low （except for GRV 022469, they are all lower than $5）. A scenario for the history of the H-chondrite parent body is proposed that suggests the duration of the shock events in the H-chondrite parent bodies was much shorter than those in L-chondrite parent bodies. Also, the pressure may have been released more quickly, and consequently, the high-pressure phases should be easily preserved. However, the parent bodies of the H-chondrites may have been exposed to high temperatures for a longer time after the shock event, so the high-pressure phases formed by solid transformation might have retro-metamorphosed to low-pressure ones; its peak pressure is estimated to be less than 15 GPa. Wadsleyite was found in a shock vein in GRV022469, as confirmed by the Raman spectrometer. Petrological and mineralogical characteristics support the idea that the wadsleyite was formed by solid-state transformation.展开更多
Three new carbonaceous chondrites (GRV 020025,021579 and 022459) collected from the Grove Mountains (GRV), Antarctica, have been classified as the CM2, CO3 and CV3 chondrites, respectively. A total of 27 Ca- and Al-ri...Three new carbonaceous chondrites (GRV 020025,021579 and 022459) collected from the Grove Mountains (GRV), Antarctica, have been classified as the CM2, CO3 and CV3 chondrites, respectively. A total of 27 Ca- and Al-rich inclusions have been found in the three meteorites, which are the earliest assemblages formed in the solar nebula. Most of the inclusions are intensively altered, with abundant phyllosilicates in the inclusions from GRV 020025 and FeO enrichment of spinel in those from GRV 022459. Except for one spinel-spherule in each of GRV 020025 and 021579, all the inclusions can be classified as Type A-like or spinel-pyroxene-rich inclusions, and they probably represent the continuum of solar nebular condensation. In addition, most of the inclusions in these meteorites share much similarity in both petrography and mineral chemistry, suggesting a similar origin of Ca-Al-rich inclusions in various chondrites.展开更多
Petrography and mineral chemistry of 24 ordinary chondrites from the Grove Mountains, Antarctica, have been studied in order to identify their chemical-petrographic types. These samples were selected from a total of 4...Petrography and mineral chemistry of 24 ordinary chondrites from the Grove Mountains, Antarctica, have been studied in order to identify their chemical-petrographic types. These samples were selected from a total of 4448 Grove Mountains (GRV) meteorites collected during the 19th Chinese Antarctic Research Expedition so as to make an estimation of the large GRV meteorite collection. The chemical-petrographic types of these meteorites are presented below: 1 H3,2 H4, 4 H5, 2 H6, 1 L4, 7 L5, 5 L6, 1 LL4 and 1 LL6. The new data weaken the previous report that unequilibrated ordinary chondrites are unusually abundant in the Grove Mountains region. However, this work confirms significant differences in distribution patterns of chemical-petrographic types between the Grove Mountains and other regions in Antarctica. Many of these meteorites show significant terrestrial weathering, probably due to a high abundance ratio of meteorites found in moraines to those on blue ice. Nine meteorites experienced severe shock metamorphism, as evidenced by undulose extinction and intense fracturing of silicates and presence of shock-induced melt veins and pockets. These heavily shocked meteorites provided us with natural samples for the study of high-pressure polymorphs of minerals.展开更多
The Ningqiang meteorite is a fall carbonaceous chondrite, containing various Ca-, Al-rich inclusions that usually escaped from secondary events such as high-temperature heating and low- temperature alteration. However...The Ningqiang meteorite is a fall carbonaceous chondrite, containing various Ca-, Al-rich inclusions that usually escaped from secondary events such as high-temperature heating and low- temperature alteration. However, it has not yet been classified into any known chemical group. In order to address this issue, 41 elements of the bulk Ningqiang meteorite were analyzed using inductively coupled plasma mass spectrometry （ICP-MS） and inductively coupled plasma atom emission spectrometry （ICP-AES） in this study. The Allende （CV3） carbonaceous chondrite and the Jilin （H5） ordinary chondrite were also measured as references, and our analyses are consistent with the previous results. Rare earth and other refractory lithophile elements are depleted in Ningqiang relative to both Allende and mean CK chondrites. In addition, the REE pattern of Ningqiang is nearly flat, while that of Allende shows slight enrichment of LREE relative to HREE. Siderophile elements of Ningqiang are close to those of mean CK chondrites, but lower than those of Allende. Our new analyses indicate that Ningqiang cannot be classified into any known group of carbonaceous chondrites, consistent with previous reports.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
Shock effects of 93 Grove Mountains （GRV） ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-i...Shock effects of 93 Grove Mountains （GRV） ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-induced veins and pockets show various microtextures, decomposition and phase transformation of minerals. The confirmed high-pressure polymorphs of silicates are ringwoodite, majorite, pyroxene glass and maskelynite. Based on the shock effects and assemblages of high-pressure minerals, shock stages of all of 93 GRV ehondrites were classified. In comparison with literature, the Grove Mountains meteorites have a higher fraction （23 out of 93 ） of heavily shocked samples （S4--S5）. Most of the heavily shocked meteorites are L group （22 out of 23）, except for one H chondrite. The distinct shock metamorphism between H and. L groups may indicate different surface properties of their parent bodies. In addition, there is relationship between petrologic types and shock stages, with most heavily shocked samples observed in equilibrated ordinary chondrites （ especially Type 5 and 6）.展开更多
Analysis of the thermal metamorphism of the ordinary chondrites is a key premise for gaining insights into the accretion and heating of rocky bodies in the early solar system.Such an analysis also represents an essent...Analysis of the thermal metamorphism of the ordinary chondrites is a key premise for gaining insights into the accretion and heating of rocky bodies in the early solar system.Such an analysis also represents an essential condition for constraining the early thermal and evolutionary histories of asteroids and terrestrial planets.Classifying ordinary chondrites into petrologic type(type 3–6)is the criterion for studying the thermal metamorphism of their parent bodies.However,the boundary between the unequilibrated(type 3)and equilibrated(type 4–6)chondrites is ambiguous at present,thus,limiting the understanding of their thermal metamorphism.In this study,the petrology,mineralogy and chemical composition of a set of seven ordinary chondrites with different degrees of thermal metamorphism collected from Grove Mountains(Antarctica)have been studied.The results demonstrated that these chondrite samples were L3.7,L3.8,L3.9,L3.9/4,L4,L5 and L6 type meteorites,with optimal correlations of Si,Mg,Fe,Mn and Ca with equilibrium degree of the olivine and low-calcium pyroxene and petrologic type.In this respect,the multi-parameter classification standard PMD(SiO2)-PMD(MgO)-PMD(MnO)-PMD(CaO)based on the percent mean deviation(PMD)of the chemical compositions of the olivine and low-calcium pyroxene was proposed to distinguish between the unequilibrated and equilibrated meteorites.The proposed standard exhibited high“resolution”in terms of classification,thus,also deepening the understanding of the effect of the silicate mineral composition in the thermal metamorphism of chondrites.Highlights The chemical groups and petrologic types of the selected seven Antarctic chondrites were L3.7,L3.8,L3.9,L3.9/4,L4,L5 and L6.A new method for petrologic type classification is proposed to distinguish the unequilibrated and equilibrated chondrites.The above developed multi-parameter system exhibited high“resolution”in terms of classification.展开更多
Petrography and mineral chemistry of four carbonaceous chondrites （ GRV 020017, GRV 020025, GRV 021579, GRV 022459 ） collected from the Grove Mountains （ GRV）, Antarctica, were reported here. All four chondrites a...Petrography and mineral chemistry of four carbonaceous chondrites （ GRV 020017, GRV 020025, GRV 021579, GRV 022459 ） collected from the Grove Mountains （ GRV）, Antarctica, were reported here. All four chondrites are unequilibrated, as indicated by well shaped chondrules and the chemical variations of olivine and low-Ca pyroxene. The modal abundance ratio of matrix/chondrule are 2 （ GRV 020017）, 2. 8 （ GRV 020025 ）, l. 2 （ GRV 021579 ）, 1 （ GRV 022459 ）. GRV 022459 has the largest chondrules （0.6--2.0 ram）. A total of 30 Ca-Al-rich inclu- sions were found in the four meteorites. Most inclusions were highly altered, with a- bundant phyllosilicates in the inclusions of GRV 020017 and GRV 020025. On the base of petrography and mineral chemistry, these chondrites are classified as CM2 （GRV 020017 and 020025）, CO3 （GRV 021579） and CV3 （GRV 022459）.展开更多
Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains （GRV）, Antarctica, were presented and their. Weathering effect, shock metamorphism and type distribution patterns were discu...Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains （GRV）, Antarctica, were presented and their. Weathering effect, shock metamorphism and type distribution patterns were discussed in this study. Among them, six are unequilibrated ordinary chondrites, including 3 H3 and 3 L3 ; and 92 meteorites are equilibrated ordinary chondrites, including 24 H-group （ 13 H4, 10 H5, 1 H6）, 64 L-group （2 L4, 44 L5, 18 L6） and 4 LL-group （3 LL4, 1 LL5）. Most GRV ehondrites （ 〉 90% ） displayed minor weathering effect （ W1 and W2）. About half of the meteorites experienced severe shock metamorphism. They commonly contain shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals. In addition, the Grove Mountains collection seems to have more abundant unequilibrated and L group ordinary ehondrites compared to the US Antarctic meteorite collection which were mainly found along the Transantarctic Mountains.展开更多
The carbonaceous chondrites are intriguing and unique in the sense that they are the only rocks that provide pristine records of the early solar nebular processes. We report here results of a detailed mineralogical, c...The carbonaceous chondrites are intriguing and unique in the sense that they are the only rocks that provide pristine records of the early solar nebular processes. We report here results of a detailed mineralogical, chemical, amino acid and isotopic studies of a recently observed fall at Mukundpura, near Jaipur in Rajasthan, India. Abundance of olivines in this meteorite is low and of serpentine minerals is high. FeO/SiO_2 = 1.05 in its Poorly Characterized Phases(PCP) is similar to that observed in other CM2.0 chondrites. The water content of ～9.8 wt.% is similar to that found in many other CM chondrites.Microscopic examination of matrix shows that its terrestrial weathering grade is WO but aqueous parent body alteration is high, as reflected in low abundance of identifiable chondrules and abundant remnants of chondrules(～7%). Thus, most of the chondrules formed initially have been significantly altered or dissolved by aqueous alterations on their parent bodies. The measured bulk carbon(2.3%) and nitrogen content and their isotopic(δ^(13)C =-5.5‰, δ^(15)N = 23.6%0) composition is consistent with CM2.0 classification probably bordering CM1. Several amino acids such as Alanine, Serine, Proline, Valine, Threonine,Leucine, Isoleucine, Asparagine and Histamine are present. Tyrosine and Tryptophan may occur in trace amounts which could not be precisely determined. All these data show that Mukundpura chondrite lies at the boundary of CM2.0 and CM1 type carbonaceous chondrites making it one of the most primitive chondrites.展开更多
The hydroxyl in phyllosilicate minerals is the most common occurrence of water in primitive meteorites. Direct hydrogen isotopic analysis of this water component using an ion microprobe has been made in some glassy or...The hydroxyl in phyllosilicate minerals is the most common occurrence of water in primitive meteorites. Direct hydrogen isotopic analysis of this water component using an ion microprobe has been made in some glassy or phyllosilicate spherules from the Al Rais (CR) and Orgueil (CI) chondrites. The spherules from Al Rais show large deuterium excesses (δD = +200 -+800‰) relative to terrestrial standards, whereas deuterium-enrichments in the spherules from Orgueil are much smaller (δD = +40 - +130‰). The phyllosilicate spherules are products of aqueous alteration of glassy precursors. In Al Rais the phyllosilicate spherules have relatively higher δD values than the glassy ones, indicating that water introduced during aqueous alteration was deuterium-enriched. The deuterium-enrichments in the phyllosilicate spherules from Orgueil could result from isotopic exchange under thermodynamic conditions within the solar nebula. The much larger δD excesses of the Al Rais spherules, however, cannot be attributed to the similar process; instead, an interstellar origin needs to be invoked.展开更多
基金ISRO-RESPOND GAP3332 and PMN-MOES GAP2175 Project support this work.
文摘Extraterrestrial dust exhibits a wide range of textural,chemical and oxygen isotopic compositions due to the heterogeneity of their precursors and modification during atmospheric entry.Experimental heating provides an opportunity to investigate the relationship between thermal processing and micrometeorite composition for a known precursor material.We conducted experiments to simulate the atmospheric entry of micrometeorites(MMs)using controlled,short-duration(10-50 s)flash heating(400-1600℃)of CI chondrite chips(<1500µm)in atmospheric air(1 bar,21%O2)combined with microanalysis(textures,chemical and isotopic compositions)of the experimental products.The heated chips closely resemble natural samples,with materials similar to unmelted MMs,partially melted(scoriaceous)MMs and fully melted cosmic spherules produced.We reproduced several key features such as dehydration cracks,magnetite rims,volatile gas release,vesicle formation and coalescence,melting and quench cooling.Our parameter space allows for discriminating peak temperature and heating duration effects.Peak temperature is the first-order control on MM mineralogy,while heating duration controls vesicle coalescence and homogenization.When compared against previous heating experiments,our data demonstrates that CI chondrite dust is more thermally resistant,relative to CM chondrite dust,by approximately+200℃.The 207 measurement of O-isotopes allows,for the first time,petrographic effects(such as volatile degassing and melting)to be correlated against bulk O-isotope evolution.Our results demonstrate findings applicable to CI chondrites and potentially to all fine-grained hydrated carbonaceous chondrite dust grains:(1)O-isotope variations arising during sub-solidus heating are dominated by the release of water from phyllosilicates,forcing the residual MM composition towards its anhydrous precursor composition.(2)Oxygen isotope compositions undergo the most significant changes at supra-solidus temperatures.As previously demonstrated and now empirically confirmed,most of these changes are driven by a mass-dependent fractionation effect caused by evaporation,which shifts residual rock compositions toward heavier values.Mixing with atmospheric air alters compositions toward the terrestrial fractionation line.Notably,these two processes do not begin simultaneously.Our data indicate that at 1200℃,isotopic evolution is dominated by evaporative mass loss.However,at higher temperatures(1400-1600℃),both pronounced evaporation and mixing with atmospheric oxygen become active,resulting in a more complex isotopic signature.(3)The total change in Δ17O during heating up to 1600℃is<3‰and in most scenarios<2‰.
基金supported by National Natural Science Foundation of China(grant no.42403041)Scientific Base and Talent Special Projects of Guangxi(grant no.AD23026084)Scientific Research Foundation of Guilin University of Technology(GUTQDJJ6614023).
文摘NWA 16080 is a representative reduced CV carbonaceous chondrite(CV_(red)),consisting mainly of chon-drules(47 vol%)and matrix(42 vol%),along with minor quantities of calcium-and aluminum-rich inclusions(CAI)and amoeboid olivine aggregates(AOA)(CAI+AOA,6 vol%)and opaque minerals(5 vol%).The chondrules exhibit well-preserved outlines and can be categorized into Type Ⅰ(Fa<10)and Type Ⅱ(Fa>10).They primarily consist of magnesium-rich olivine,along with both low-Ca and high-Ca pyroxenes,and contain minor amounts of secondary plagioclase.Olivines present in chondrules display compositional zoning characterized whereas the matrix is composed of fine-grained olivine.Nickel-rich metal and nickel-poor sulfides are also present,along with trace amounts of magnetite.In contrast to standard oxidized CV chondrites(CV_(ox)),the presence of high metal,Ni-poor sulfides,and reduced magnetite in NWA 16080 indicates a more reduced parent-body environment.Shock metamorphism is classified as mild(S1),while terrestrial weathering is characterized as low(W2).Raman spectroscopy indicates a diverse spectrum of organic matter(OM)maturity:certain areas exhibit characteristics akin to other CV_(red) chondrites,whereas others reach maturity levels comparable to those observed in CV_(ox) chondrites.The Raman parameters indicate that this meteorite is classified as approximately type 3.4 to 3.5.The overlapping OM maturity with certain CV_(ox) chondrites provides a contradiction to the anticipated depth-thermal layering outlined in the onion-shell model.This suggests that the CV parent body probably experienced more intricate processes,including impacts and fluid-rock interactions,rather than merely depth-dependent heating.
基金supported by Science and Technology Planning Project of Guangdong Province,2023B1212060048.
文摘Copper possesses very strong chacophile properties,but under the conditions found in meteorites,its behavior is like that of siderophile elements.The Suizhou meteorite is a highly shocked L6 chondrite.Troilite and taenite are considered the main primary carrier of copper in this meteorite,and the post-shock thermal episode is considered the main reason that elemental Cu migrates from its original host phase and forms metallic grains.The Suizhou meteorite contains a few very thin shock melt veins.The occurrence and behavior of metallic copper in this meteorite were studied by optical microscopic examination,electron microprobe analyses,and high-resolution X-ray elemental intensity mapping.Our results show that metallic copper is abundant in the Suizhou chondritic rock.Metallic copper grains adjacent to small troilite grains inside FeNi metal are the most common occurrence,and those at the FeNi metal–troilite interface are the second most common case.The metallic copper grains occurring at the interface of FeNi metal/troililte and silicate are rather rare.Metallic copper grains are not observed within the Suizhou shock veins,Instead,Cu in elemental form is transferred through shock metamorphism into FeNi metal+troilite intergrowths.Four diff erent occurrence types of Cu in the FeNi metal+troilite intergrowths have been identifi ed:the concentrations of Cu in the FeNi+FeS intergrowths for four occurrence types are rather close,we estimate it might be lower than 1 wt%.
基金supported by Korea Polar Research Institute project PE24050.
文摘The mineralogy and petrography of EET 14017 were studied using optical microscope,scanning electron microscope,electron microprobe,and micro-Raman.The mineral chemistry of olivine,pyroxene,plagioclase,spinel,and Fe-Ni metal in EET 14017 is comparable to that of previously studied L/LL3.0x chondrites.In particular,the Cr2O3 content in the ferroan chondrule olivine and the excess silica component,[]Si4O8,in the plagioclase lead us to conclude that EET 14017 belongs to subtype 3.05.Raman spectral data of carbonaceous matter from the matrix of EET 14017 suggest a higher degree of thermal metamorphism,probably due to terrestrial weathering in Antarctica.EET 14017 and some of the other L/LL3.0x chondrites from the EET region are possibly a pair,since they have similar Cr2O3 contents of ferroan chondrule olivines and Raman spectral data,and moreover they were also found in a restricted region of the blue ice field.The plagioclase in some chondrules is a late crystal phase in the chondrule melt,which may constrain the timing of chondrule formation and cooling rate.If more L/LL3.0x chondrites like EET 14017 from Antarctica are identified,they would be excellent source material for studying the early evolution of the Solar System.
基金supported by the Pilot Project of Knowledge Innovation of Chinese Academy of Sciences (Grant no.KZCX2-YW-110)the National Natural Science Foundation of China(Grant nos. 40673055 and 40473037)the Open Foundation of Key Laboratory of Geological Engineering Centre of Guangxi Province (Grantno. Gui Ke Neng 07109011-K024)
文摘The shock metamorphism of 47 H group chondrites （H-chondrites） from the Grove Mountains including undulatory extinction, planar fractures, mosaic extinction, shock veins and pockets, and dendritic eutectic metal-sulfide, is observed through optical microscope. The textures and assemblages of shock veins in these H-chondrites are examined by the scanning electron microscope. Based on observations of the above shock effects, the shock stages of the 47 H-chondrites are classified into S1（5）, S2（19）,S$3（14）, S4（8） and S5（1）. Of these H-chondrites, GRV 022469 has the highest（S5） shock stage. The comparison of shock stages in these H-chondrites with L group chondrites（L-chondrites） indicates that the shock metamorphism of H-chondrites is relatively low （except for GRV 022469, they are all lower than $5）. A scenario for the history of the H-chondrite parent body is proposed that suggests the duration of the shock events in the H-chondrite parent bodies was much shorter than those in L-chondrite parent bodies. Also, the pressure may have been released more quickly, and consequently, the high-pressure phases should be easily preserved. However, the parent bodies of the H-chondrites may have been exposed to high temperatures for a longer time after the shock event, so the high-pressure phases formed by solid transformation might have retro-metamorphosed to low-pressure ones; its peak pressure is estimated to be less than 15 GPa. Wadsleyite was found in a shock vein in GRV022469, as confirmed by the Raman spectrometer. Petrological and mineralogical characteristics support the idea that the wadsleyite was formed by solid-state transformation.
基金This work was supported by the pilot project of knowledge-innovation of Chinese Academy of Sciences(Grant No:KZCX3-SW-123)the National Natural Science Foundation of China(Grant No.40025311).
文摘Three new carbonaceous chondrites (GRV 020025,021579 and 022459) collected from the Grove Mountains (GRV), Antarctica, have been classified as the CM2, CO3 and CV3 chondrites, respectively. A total of 27 Ca- and Al-rich inclusions have been found in the three meteorites, which are the earliest assemblages formed in the solar nebula. Most of the inclusions are intensively altered, with abundant phyllosilicates in the inclusions from GRV 020025 and FeO enrichment of spinel in those from GRV 022459. Except for one spinel-spherule in each of GRV 020025 and 021579, all the inclusions can be classified as Type A-like or spinel-pyroxene-rich inclusions, and they probably represent the continuum of solar nebular condensation. In addition, most of the inclusions in these meteorites share much similarity in both petrography and mineral chemistry, suggesting a similar origin of Ca-Al-rich inclusions in various chondrites.
文摘Petrography and mineral chemistry of 24 ordinary chondrites from the Grove Mountains, Antarctica, have been studied in order to identify their chemical-petrographic types. These samples were selected from a total of 4448 Grove Mountains (GRV) meteorites collected during the 19th Chinese Antarctic Research Expedition so as to make an estimation of the large GRV meteorite collection. The chemical-petrographic types of these meteorites are presented below: 1 H3,2 H4, 4 H5, 2 H6, 1 L4, 7 L5, 5 L6, 1 LL4 and 1 LL6. The new data weaken the previous report that unequilibrated ordinary chondrites are unusually abundant in the Grove Mountains region. However, this work confirms significant differences in distribution patterns of chemical-petrographic types between the Grove Mountains and other regions in Antarctica. Many of these meteorites show significant terrestrial weathering, probably due to a high abundance ratio of meteorites found in moraines to those on blue ice. Nine meteorites experienced severe shock metamorphism, as evidenced by undulose extinction and intense fracturing of silicates and presence of shock-induced melt veins and pockets. These heavily shocked meteorites provided us with natural samples for the study of high-pressure polymorphs of minerals.
基金This study was supported by the National Natural Science Foundation （Grant 40473038）.
文摘The Ningqiang meteorite is a fall carbonaceous chondrite, containing various Ca-, Al-rich inclusions that usually escaped from secondary events such as high-temperature heating and low- temperature alteration. However, it has not yet been classified into any known chemical group. In order to address this issue, 41 elements of the bulk Ningqiang meteorite were analyzed using inductively coupled plasma mass spectrometry （ICP-MS） and inductively coupled plasma atom emission spectrometry （ICP-AES） in this study. The Allende （CV3） carbonaceous chondrite and the Jilin （H5） ordinary chondrite were also measured as references, and our analyses are consistent with the previous results. Rare earth and other refractory lithophile elements are depleted in Ningqiang relative to both Allende and mean CK chondrites. In addition, the REE pattern of Ningqiang is nearly flat, while that of Allende shows slight enrichment of LREE relative to HREE. Siderophile elements of Ningqiang are close to those of mean CK chondrites, but lower than those of Allende. Our new analyses indicate that Ningqiang cannot be classified into any known group of carbonaceous chondrites, consistent with previous reports.
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.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(kzcx2-yw-110,KZCX2-YW-Q08)
文摘Shock effects of 93 Grove Mountains （GRV） ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-induced veins and pockets show various microtextures, decomposition and phase transformation of minerals. The confirmed high-pressure polymorphs of silicates are ringwoodite, majorite, pyroxene glass and maskelynite. Based on the shock effects and assemblages of high-pressure minerals, shock stages of all of 93 GRV ehondrites were classified. In comparison with literature, the Grove Mountains meteorites have a higher fraction （23 out of 93 ） of heavily shocked samples （S4--S5）. Most of the heavily shocked meteorites are L group （22 out of 23）, except for one H chondrite. The distinct shock metamorphism between H and. L groups may indicate different surface properties of their parent bodies. In addition, there is relationship between petrologic types and shock stages, with most heavily shocked samples observed in equilibrated ordinary chondrites （ especially Type 5 and 6）.
基金funded by Strategic Priority Research Program of Chinese Academy of Sciences(XDB 41000000)Project funded by China Postdoctoral Science Foundation(2020M673557XB)+4 种基金Guangxi Natural Science Foundation under Grant No.2020JJB150056Civil Aerospace Pre Research Project(D020302 and D020206)Guangxi Scientific Base and Talent Special Projects(No.AD1850007)Foundation of Guilin University of Technology(GUTQDJJ2019165)the grant from Key Laboratory of Lunar and Deep Space Exploration,CAS(LDSE201907).
文摘Analysis of the thermal metamorphism of the ordinary chondrites is a key premise for gaining insights into the accretion and heating of rocky bodies in the early solar system.Such an analysis also represents an essential condition for constraining the early thermal and evolutionary histories of asteroids and terrestrial planets.Classifying ordinary chondrites into petrologic type(type 3–6)is the criterion for studying the thermal metamorphism of their parent bodies.However,the boundary between the unequilibrated(type 3)and equilibrated(type 4–6)chondrites is ambiguous at present,thus,limiting the understanding of their thermal metamorphism.In this study,the petrology,mineralogy and chemical composition of a set of seven ordinary chondrites with different degrees of thermal metamorphism collected from Grove Mountains(Antarctica)have been studied.The results demonstrated that these chondrite samples were L3.7,L3.8,L3.9,L3.9/4,L4,L5 and L6 type meteorites,with optimal correlations of Si,Mg,Fe,Mn and Ca with equilibrium degree of the olivine and low-calcium pyroxene and petrologic type.In this respect,the multi-parameter classification standard PMD(SiO2)-PMD(MgO)-PMD(MnO)-PMD(CaO)based on the percent mean deviation(PMD)of the chemical compositions of the olivine and low-calcium pyroxene was proposed to distinguish between the unequilibrated and equilibrated meteorites.The proposed standard exhibited high“resolution”in terms of classification,thus,also deepening the understanding of the effect of the silicate mineral composition in the thermal metamorphism of chondrites.Highlights The chemical groups and petrologic types of the selected seven Antarctic chondrites were L3.7,L3.8,L3.9,L3.9/4,L4,L5 and L6.A new method for petrologic type classification is proposed to distinguish the unequilibrated and equilibrated chondrites.The above developed multi-parameter system exhibited high“resolution”in terms of classification.
基金supported by the Doctor's Foundation of Hunan University of Science and Technology(Grant No.E50806)
文摘Petrography and mineral chemistry of four carbonaceous chondrites （ GRV 020017, GRV 020025, GRV 021579, GRV 022459 ） collected from the Grove Mountains （ GRV）, Antarctica, were reported here. All four chondrites are unequilibrated, as indicated by well shaped chondrules and the chemical variations of olivine and low-Ca pyroxene. The modal abundance ratio of matrix/chondrule are 2 （ GRV 020017）, 2. 8 （ GRV 020025 ）, l. 2 （ GRV 021579 ）, 1 （ GRV 022459 ）. GRV 022459 has the largest chondrules （0.6--2.0 ram）. A total of 30 Ca-Al-rich inclu- sions were found in the four meteorites. Most inclusions were highly altered, with a- bundant phyllosilicates in the inclusions of GRV 020017 and GRV 020025. On the base of petrography and mineral chemistry, these chondrites are classified as CM2 （GRV 020017 and 020025）, CO3 （GRV 021579） and CV3 （GRV 022459）.
基金supported by the Doctor's Foundation of Hunan University of Science and Technology(Grant No.E50806)
文摘Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains （GRV）, Antarctica, were presented and their. Weathering effect, shock metamorphism and type distribution patterns were discussed in this study. Among them, six are unequilibrated ordinary chondrites, including 3 H3 and 3 L3 ; and 92 meteorites are equilibrated ordinary chondrites, including 24 H-group （ 13 H4, 10 H5, 1 H6）, 64 L-group （2 L4, 44 L5, 18 L6） and 4 LL-group （3 LL4, 1 LL5）. Most GRV ehondrites （ 〉 90% ） displayed minor weathering effect （ W1 and W2）. About half of the meteorites experienced severe shock metamorphism. They commonly contain shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals. In addition, the Grove Mountains collection seems to have more abundant unequilibrated and L group ordinary ehondrites compared to the US Antarctic meteorite collection which were mainly found along the Transantarctic Mountains.
基金carried out with the support of MOES-PMN and PLANEX (Physical Research Laboratory, Ahmedabad) programs
文摘The carbonaceous chondrites are intriguing and unique in the sense that they are the only rocks that provide pristine records of the early solar nebular processes. We report here results of a detailed mineralogical, chemical, amino acid and isotopic studies of a recently observed fall at Mukundpura, near Jaipur in Rajasthan, India. Abundance of olivines in this meteorite is low and of serpentine minerals is high. FeO/SiO_2 = 1.05 in its Poorly Characterized Phases(PCP) is similar to that observed in other CM2.0 chondrites. The water content of ～9.8 wt.% is similar to that found in many other CM chondrites.Microscopic examination of matrix shows that its terrestrial weathering grade is WO but aqueous parent body alteration is high, as reflected in low abundance of identifiable chondrules and abundant remnants of chondrules(～7%). Thus, most of the chondrules formed initially have been significantly altered or dissolved by aqueous alterations on their parent bodies. The measured bulk carbon(2.3%) and nitrogen content and their isotopic(δ^(13)C =-5.5‰, δ^(15)N = 23.6%0) composition is consistent with CM2.0 classification probably bordering CM1. Several amino acids such as Alanine, Serine, Proline, Valine, Threonine,Leucine, Isoleucine, Asparagine and Histamine are present. Tyrosine and Tryptophan may occur in trace amounts which could not be precisely determined. All these data show that Mukundpura chondrite lies at the boundary of CM2.0 and CM1 type carbonaceous chondrites making it one of the most primitive chondrites.
文摘The hydroxyl in phyllosilicate minerals is the most common occurrence of water in primitive meteorites. Direct hydrogen isotopic analysis of this water component using an ion microprobe has been made in some glassy or phyllosilicate spherules from the Al Rais (CR) and Orgueil (CI) chondrites. The spherules from Al Rais show large deuterium excesses (δD = +200 -+800‰) relative to terrestrial standards, whereas deuterium-enrichments in the spherules from Orgueil are much smaller (δD = +40 - +130‰). The phyllosilicate spherules are products of aqueous alteration of glassy precursors. In Al Rais the phyllosilicate spherules have relatively higher δD values than the glassy ones, indicating that water introduced during aqueous alteration was deuterium-enriched. The deuterium-enrichments in the phyllosilicate spherules from Orgueil could result from isotopic exchange under thermodynamic conditions within the solar nebula. The much larger δD excesses of the Al Rais spherules, however, cannot be attributed to the similar process; instead, an interstellar origin needs to be invoked.
