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1.
综述了非球陨石（铁陨石，石铁陨石和无球粒陨石）在成分结构方面的非分异成因证据，推断其成因是：星云盘中心层中的星云发生气－液凝聚作用形成的熔滴，在较高温度下彼此合并形成了较大熔体，熔体固化后形成该类陨石母体。根据Ｃ１陨石不含球粒和其它成分特征，推断它们是星云只发生气－固凝聚作用的产物。对近年来新发现的一些特殊成分的碳质球粒陨石进行了综合分析，暂定名为类Ｃ１陨石。通过类Ｃ１陨石与其它球粒陨石及Ｃ１陨石成分结构特征的对比，推断它们是星云盘边缘层星云发生气－液－固和气－固联合凝聚作用，同时发生水化作用的产物。最后，在对所有陨石凝聚成因进行解释的基础上，建立了小行星区星云凝聚模型。 相似文献
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清镇顽火辉石球粒陨石的矿物学特征及其成因 总被引：1，自引：0，他引：1
清镇陨石以具有高度还原的矿物组合为特征。普通球粒陨石和碳质球粒陨石中的亲石元素在顽火辉石球粒陨石内显示亲铜或亲铁的性质。在该陨石中发现的矿物有陨硫钙石。硫镁矿、钾的硫化物——硫铜钾矿,含Si的铁纹石及Ni的硅化物——硅磷镍矿等。顽火辉石和斜顽火辉石具有低的FeO含量,其FeO/(FeO+MgO)比值范围为0.004—0.01。在未完全熔融的球粒中发现具尘粒状贫Ni金届包裹体的残余橄榄石颗粒。本文首次报道陨石中含Ga的闪锌矿和发现陨石中稀少的碱硅镁柱石。金属-硫化物组合显示再加热和熔融的结构特征,金属发生硫化作用并被硫化物所取代。清镇陨石(EH_3)的化学成分与EH_(4,5)球粒陨石很相似,其La/Sm比值比平均EL高,Co/Ni则比EL低。清镇陨石的形成部位比任何其他球粒陨石群更靠近太阳,可能形成于水星-金星区。 相似文献
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南极陨石的研究发现，有几个碳质球粒陨石富含与Ｃ１陨石类似的含水层状硅酸盐集合体及其角砾．其氧同位素比值也与Ｃ１接近，因而称之为类Ｃ１陨石。类Ｃ１陨石与Ｃ１陨石的区别是：类Ｃ１陨石中的含水层状硅酸盐既以基质的形式产出，也出现在球粒中；类Ｃ１陨石中含有球粒及有关组分，如球粒碎块、矿物集合体等。每个陨石中所含这些组分的数量不同，其矿物的成分也差别很大，从而说明它们形成的星云环境不同。因此笔者认为类Ｃ１陨石可能是小行星区星云盘外层的星云凝聚物受到不同程度水化作用后吸积形成的陨石。 相似文献
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太阳星云凝集过程的岩石学模式：（Ⅱ）非球陨石,C1陨石及类C1陨石的凝… 总被引：3，自引：1，他引：3
综述了非球陨石（铁陨石、石铁陨石和无球粒陨石）在成分结构方面的非分异成因证据，推断其成因是：星云盘中心层中的星云发生气－液凝聚作用形成的熔滴，在较高温度下彼此合并形成了较大熔体，熔体固化后形成该类陨石母体。根据Ｃ１陨石不含球粒和其它成分特征。推断它们是星云只发生气－固凝集作用的产物。 相似文献
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南极陨石的研究发现，有几个碳质球粒陨石富含与ＣＩ陨石类似的含水层状硅酸盐集合体及其角砾，其氧同位素比值也与ＣＩ接近，因而称之为类Ｃ１陨石。类Ｃ１陨石与Ｃ１陨石的区别是：类Ｃ１陨石中的含水层状硅酸盐既以基质的形式产出，也出现在球粒中；类Ｃ１陨石中含有球粒及有关组分，如球粒碎块、矿物集合体等。每个陨石中所含这些组分的数量不同，其矿物的成分也差别很大，从而说明它们形成的星云环境不同。因此笔者认为类Ｃ１陨 相似文献
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太阳星云凝聚过程的岩石学模型：（1）球粒陨石的凝聚成因 总被引：2，自引：2，他引：2
建立类地行星区太阳星云凝聚过程的岩石学模型，对于合理解释陨石、地球和类地行星的成因关系，探讨地球起源和估算地球的整体成分都有着重要意义。本文中根据天体化学和太阳系演化学说关于太阳星云物理化学条件的基本分析，以及实验凝聚岩石学的研究结果，推断在太阳星云盘的类地行星区中可能有星云的气－固和气－液－固两种凝聚作用发生。通过对球粒陨石中球粒和基质矿物成分及结构构造特征的对比，论证了绝大多数球粒的气－液－固凝聚成因和基质的气－固凝聚成因，并讨论了球粒陨石各化学群的凝聚成因模式。 相似文献
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1997年降落在山东省鄄城县的陨石雨,是橄榄石-古铜辉石球粒陨石。该陨石中的金属矿物主要为铁纹石和陨硫铁,其次为镍纹石,金属矿物呈填隙状分布于以橄榄石和古铜辉石为主的硅酸盐矿物粒间及球粒周围。陨石中可见由铁纹石和镍纹石组成的显微蠕虫状连晶,是陨石中金属矿物在降温冷却过程中发生固溶体分离作用而成。陨石中金属矿物的分布特征表明,金属Fe-Ni和硫化物（FeS）应该是星云凝聚不同阶段的产物。陨石中金属矿物的成分和组构特征及陨石中出现的球粒结构、橄榄石的炉条结构等特征表明,该球粒陨石是星云物质快速冷却的产物。 相似文献
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清镇陨石（EH3）硫镁矿微量元素化学特征 总被引：1，自引：0，他引：1
本文应用电子探针和中子活化分析方法详细研究了清镇陨石(EH 3)中硫镁矿的化学组成和微量元素分布、硫镁矿携带了部分HREE、高度富集钪等难熔亲石元素,论证了该矿物的高温成因,REE丰度可能与陨硫钙石互补。该矿物含有钠-硒组分,可能是顽火辉石陨石独有的组分。铬归一化的钠-钴(原子比)相关关系具有CI一致的趋势,表明其母体来自太阳组成的气体星云。 相似文献
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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. 相似文献
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Eric Quirico Michèle Bourot-denise Gilles Montagnac 《Geochimica et cosmochimica acta》2011,75(11):3088-3102
The thermal history of a series of EH3 and EL3 chondrites has been investigated by studying the degree of structural order of the organic matter (OM) located and characterized in matrix areas by Raman micro-spectroscopy. By comparison with unequilibrated ordinary chondrites (UOCs) and CO and CV carbonaceous chondrites, the following petrologic types have been assigned to various E chondrites: Sahara 97096 and Allan Hills 84206: 3.1-3.4; Allan Hills 85170 and Parsa: 3.5; Allan Hills 85119: 3.7; Qingzhen, MacAlpine Hills 88136 and MacAlpine Hills 88184: 3.6-3.7. The petrologic type of Qingzhen is consistent with the abundance of the P3 noble gas component, a sensitive tracer of the grade of thermal metamorphism. The petrologic types are qualitatively consistent with the abundance of fine-grained matrix for the whole series. No significant effects of shock processes on the structure of OM were observed. However such processes certainly compete with thermal metamorphism and the possibility of an effect cannot be fully discarded, in particular in the less metamorphosed objects. The OM precursors accreted by the EH3 and EL3 parent bodies appear to be fairly similar to those of UOCs and CO and CV carbonaceous chondrites. Raman data however show some slight structural differences that could be partly accounted for by shock processes. The metamorphic history of EH3 and EL3 chondrites has often been described as complex, in particular regarding the combined action of shock and thermal metamorphism. Because OM maturity is mostly controlled by the temperature of peak metamorphism, it is possible to distinguish between the contributions of long duration thermal processes and that of shock processes. Comparison of the petrologic types with the closure temperatures previously derived from opaque mineral assemblages has revealed that the thermal history of EH3 and EL3 chondrites is consistent with a simple asteroidal onion shell model. Thermal metamorphism in enstatite chondrites appears to be fairly similar to that which takes place in other chondrite classes. The complex features recorded by mineralogy and petrology and widely reported in the literature appear to be mostly controlled by shock processes. 相似文献
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Initial 129I/127I values (I-Xe ages) have been obtained for individual mineralogically characterized chondrules and interchondrule matrix from the enstatite chondrites Qingzhen (EH3) and Kota Kota (EH3). In view of the absence of aqueous alteration and the low-peak metamorphic temperatures experienced by these meteorites, we suggest that the I-Xe ages for the chondrules record the event in which they were formed. These ages are within the range recorded for chondrules from ordinary chondrites, demonstrating that chondrules formed during the same time interval in the source regions of both ordinary chondrites and enstatite chondrites. The timing of this chondrule-forming episode or episodes brackets the I-Xe closure age of planetesimal bodies such as the Shallowater aubrite parent body. Although chondrule formation need not have occurred close to planetesimals, the existence of planetesimals at the same time as chondrule formation provides constraints on models of this process. Whichever mechanisms are proposed to form and transport chondrules, they must be compatible with models of the protosolar nebula which predict the formation of differentiated bodies on the same timescale at the same heliocentric distance. 相似文献
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Noble gases were measured both in bulk samples (stepped pyrolysis and total extraction) and in a HF/HCl residue (stepped pyrolysis and combustion) from the Klein Glacier (KLE) 98300 EH3 chondrite. Like the bulk meteorite and as seen in previous studies of bulk type 3 E chondrites (“sub-Q”), the acid residue contains elementally fractionated primordial noble gases. As we show here, isotopically these are like those in phase-Q of primitive meteorites, but elementally they are heavily fractionated relative to these. The observed noble gases are different from “normal” Q noble gases also with respect to release patterns, which are similar to those of Ar-rich noble gases in anhydrous carbonaceous chondrites and unequilibrated ordinary chondrites (with also similar isotopic compositions). While we cannot completely rule out a role for parent body processes such as thermal and shock metamorphism (including a later thermal event) in creating the fractionated elemental compositions, parent body processes in general seem not be able to account for the distinct release patterns from those of normal Q noble gases. The fractionated gases may have originated from ion implantation from a nebular plasma as has been suggested for other types of primordial noble gases, including Q, Ar-rich, and ureilite noble gases. With solar starting composition, the corresponding effective electron temperature is about 5000 K. This is lower than inferred for other primordial noble gases (10,000-6000 K). Thus, if ion implantation from a solar composition reservoir was a common process for the acquisition of primordial gas, electron temperatures in the early solar system must have varied spatially or temporally between 10,000 and 5000 K.Neon and xenon isotopic ratios of the residue suggest the presence of presolar silicon carbide and diamond in abundances lower than in the Qingzhen EH3 and Indarch EH4 chondrites. Parent body processes including thermal and shock metamorphism and a late thermal event also cannot be responsible for the low abundances of presolar grains. KLE 98300 may have started out with smaller amounts of presolar grains than Qingzhen and Indarch. 相似文献
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安徽亳县陨石不透明矿物研究 总被引：3，自引：2，他引：3
毫县陨石的不透明矿物有陨硫铁、铁纹石、镍纹石、镍黄铁矿、镁铁尖晶石、自然铜、石墨、方铁矿、铬铁矿、钛铁矿、磁铁矿、张衡矿及x矿物等。本文对它们进行了反光显微镜鉴定、X射线分析、反射率测定和电子探针分析。总结了不同化学群的球粒陨石中FeO和MgO的含量变化规律。 相似文献
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The two textural varieties of olivine-rich Allende inclusions (rimmed and unrimmed olivine aggregates) consist primarily of a porous, fine-grained mafic constituent (inclusion matrix) that differs from the opaque meteorite matrix of CV3 chondrites by being relatively depleted in sulfides, metal grains, and (perhaps) carbonaceous material. Olivine is the most abundant mineral in Allende inclusion matrix; clinopyroxene, nepheline, sodalite, and Ti-Al-pyroxene occur in lesser amounts. Olivine in unrimmed olivine aggregates (Type 1A inclusions) is ferrous and has a narrow compositional range (Fo50–65). Olivine in rimmed olivine aggregates (Type 1B inclusions) is, on average, more magnesian, with a wider compositional range (Fo53–96). Olivine grains in the granular rims of Type 1B inclusions are zoned, with magnesian cores (Fo>80) and ferrous rinds (Fo<70). Ferrous olivines (Fo<65) in both varieties of inclusions commonly contain significant amounts of Al2O3 (as much as ~0.7 wt%), CaO (as much as ~0.4 wt%), and TiO2 (as much as ~0.2 wt%), refractory elements that probably occur in submicroscopic inclusions of Ca,Al,Ti-rich glass (rather than in the olivine crystal structure). Defocussed beam analyses of Allende matrix materials demonstrate that: (1) inclusion matrix in Type 1A inclusions is more enriched in olivine and FeO than inclusion matrix in the cores of Type 1B inclusions; (2) opaque matrix materials are depleted in feldspathoids and enriched in sulfides and metal grains relative to inclusion matrix; (3) the bulk compositions of Type 1A and Type 1B inclusions overlap; and (4) excluding sulfides and metal, the bulk compositions of Allende matrix materials cluster in a complementary pattern around the bulk composition of C1 chondrites.Inclusion matrix and meteorite matrix in Allende and other CV3 chondrites are probably relatively primitive nebular material, but a careful evaluation of the equilibrium condensation model suggests that these matrix materials do not consist of crystalline phases that formed under equilibrium conditions in a relatively cool gas of solar composition. Allende inclusion matrix is interpreted as an aggregate of condensates that formed under relatively oxidizing, non-equilibrium conditions from supercooled, supersaturated vapors produced during the vaporization of interstellar dust by aerodynamic drag heating in the solar nebula; CV3 meteorite matrix contains, in addition, a proportion of interstellar material that was heated (but not vaporized) in the nebula. Granular olivine in rimmed olivine aggregates may have formed during the recrystallization and incipient melting of aggregates of inclusion matrix in the nebula. The mineral chemistry of matrix olivine in Allende seems to have been established by three different processes: non-equilibrium vapor → solid condensation; recrystallization and partial melting in the nebula; and equilibration (without textural homogenization) in the meteorite parent body. 相似文献
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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. 相似文献
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We report the results of rare earth elements (REEs) and U-Th inventory of individual minerals (oldhamite, enstatite and niningerite) in two of the most unequilibrated and primitive EH3 known so far, ALHA77295 and Sahara 97072. Under the highly reducing condition that prevailed during the formation of enstatite chondrites, REEs are mainly chalcophile and concentrated in oldhamite. The study is guided by detailed petrographic investigations of the individual minerals in chondrules, complex sulfide-metal clasts and enstatite-dominated matrices.We developed two textural parameters in order to resolve the evolution of oldhamite condensates and their residence in the solar gas prior to their accretion in the individual objects or in matrices and relate these textural features to the measured REE patterns of the individual oldhamite crystals. These textural parameters are the crystal habit of oldhamite grains (idiomorphic or anhedral) and their host assemblages. REE concentrations were measured by SIMS and LA-ICPMS.Oldhamite grains display REE enrichments (10-100 × CI). Four types of REE patterns are encountered in oldhamite in ALHA77295. In general the REE distributions cannot be assigned to a specific oldhamite-bearing assemblage. The most represented REE pattern is characterized by both slight to large positive Eu and Yb anomalies and is enriched in light REEs relative to heavy REEs. This pattern is present in 97% of oldhamite in Sahara 97072, suggesting a different source region in the reduced part of the nebula or different parental EH asteroids for the two EH3 chondrites. Different parental asteroids are also supported by MgS-FeS zoning profiles in niningerite grains adjacent to troilite revealing both normal and reverse zoning trends and different MnS contents. The observed homogeneity of REE distribution in oldhamite grains in Sahara 97072 is not related to the mild metamorphic event identified in this meteorite that caused breakdown of the major K- and Rb-bearing sulfide (djerfisherite).REE concentrations in enstatite range between 0.2 and 8 × CI. Hence, enstatite is an important REE host next to oldhamite. Most patterns are characterized by negative Eu and Yb anomalies. Niningerites are negligible contributors to bulk EH3 REE inventory. Average positive Eu and Yb anomalies observed in most oldhamite are complimentary to the negative ones in enstatite thus explaining the flat patterns of the bulk meteorites. The condensation calculations based on cosmic abundances predict that the first oldhamite condensates should have flat REE patterns with Eu and Yb depletions since Eu and Yb condense at lower temperature than other REE. However, this pattern is seen in enstatite. Our findings are at odds with the predicted negative Eu and Yb anomalies in oldhamite earliest condensates from a closed system in a reduced solar source. Our petrographic, mineral chemistry and REE abundances of oldhamite, enstatite and niningerite discards an origin of oldhamite by impact melting (Rubin et al., 2009).Our results do not support in first order the scenario of the incorporation of REE in the Earth’s core to explain 142Nd excess in terrestrial samples relative to chondrites because oldhamite is the major REE carrier phase and has super-chondritic Sm/Nd ratios. 相似文献