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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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一个新的太阳星云凝聚岩石学模型：（I）陨石的凝聚成因 总被引：1，自引：0，他引：1
大量研究已确证陨石是保留原始成分和结构特征最多的太阳星云凝聚物，而小行星带又是陨石的源区。因此，本研究是在对陨石的化学成分，矿物学和岩石学特征，以及目前对太阳星云压力密度的计算和蒸发－凝聚实验结果进行分析的基础上，探讨陨石的凝聚成因，从而为建立小行星区乃至整个类地行星萄星云凝聚模型提供依据。 相似文献
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在建立了小行星区星云凝聚模型的基础上，对类地行星区中上物质（硅酸盐、氧化物、金属、硫化物等）的凝聚作用，以及凝聚物的水化作用进行了讨论，进而建立了包括小行星区在内的整个类地行星区的星云凝聚模式。根据地球核慢质量比和关于地球初期演化的研究结果；使用顽火辉石球粒陨石和Ｃ１陨石的化学成分分别做为地球形成区中类顽火辉石球粒陨石质星子和类Ｃ１陨石质星子的成分数据；假定类顽火辉石无球粒陨石质星子的成分与类顽火辉石球粒陨石质星子的硅酸盐部分成分相同，计算出原始地球可能由１．５８％的类铁陨石质星子、１３．９％的类顽火辉石无球粒陨石质星子、８２．５２％类顽火辉石球粒陨石质星子、２％的类Ｃ１陨石质星子组成。 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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太阳星云凝集过程的岩石学模型：（Ⅲ）类地行星区星云凝集作用和地球… 总被引：2，自引：0，他引：2
在建立了小行星星云凝聚模型的基础上，对类地行星区中土物质（硅酸盐、氧化物、金属、硫化物等）的凝聚作用，以及凝聚物的水化作用进行了讨论。进而建立了包括小行星区在内的整个类地行星区的星云凝聚模式。根据地球核幔质量比和关于地球初期演化的研究结果：使用顽光辉石球粒陨石和Ｃ１陨石的化学成分分别做为地球形成区中类顽光辉石球粒陨石质星子和类Ｃ１陨石质星子和类Ｃ１陨石质星子的成分数据，假定类顽光辉石无球粒陨石质昨 相似文献
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富Ca、Al包体(简称CAI)形成于太阳星云演化的最初始阶段,其成因模式主要包括:气—固凝聚、熔融结晶和部分熔融以及高温蒸发作用等。最近,通过对不同球粒陨石化学群中的CAI进行岩石学特征对比研究,发现不同化学群中的CAI具有相似的大小和类型分布特征,表明不同球粒陨石化学群中的CAI极可能具有相似的起源。该结果,与前人的氧同位素、Al—Mg同位素体系以及稀土元素等研究得到的结论一致。不同球粒陨石化学群中的CAI具有相似的成因,并很可能形成于太阳星云的相同区域,随后迁移到不同球粒陨石群的吸积区域。 相似文献
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类地行星挥发性元素普遍亏损很可能是由于太阳星云早期剧烈的太阳活动引起的。当气体、尘粒、挥发性元素和水被驱赶出内太阳系时，只有米级到公里级的物质保存下来并堆积成星子，最终吸积星子形成类地行星。我们认为类地行星的初始物质主要是已分异的星子和一些未分异的球粒陨石质星子或不同类型的陨石母体，最靠近太阳形成的星子具有最低的ＦｅＯ／（ＦｅＯ＋ＭｇＯ）值，水星是在靠近太阳的高度还原条件下吸积成分类似ＥＨ球粒陨石的星子形成的。地球的初始物质为分异的铁陨石及Ｈ群球粒陨石。随着距太阳距离增大及温度降低，陨石形成的部位大致为：ＥＨ、ＥＬ－ＩＡＢ－ＳＮＣ（辉玻无球粒陨石、辉橄无球粒陨石、纯橄无球粒陨石）－Ｅｕｃ（钙长辉长无球粒陨石）－Ｈ、Ｌ、ＬＬ－ＣＶ、ＣＭ、ＣＯ－Ｃｌ－彗星。物体之间、星子之间及行星与星子之间的碰撞对太阳系的形成和演化起着重要的作用。 相似文献
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陨石是来自含气体-尘粒的太阳早期星云盘凝聚和吸积的原始物质,大多数原始物质因吸积后的作用过程而改变（如月球、地球及火星样品）,但有一些却完整的保存下来（如球粒陨石或球粒陨石中的难熔包体）。这些原始的物质通常依据同位素丰度特征来识别,依据其矿物-岩石学特征和成因可将已知的陨石划分许多更小的类型。陨石学及天体化学的新近进展包括：新近识别的陨石群;发现新类型球粒陨石及行星际尘粒中发现前太阳和星云组分;利用短寿命放射性核素完善了早期太阳系年代学;洞察宇宙化学丰度、分馏作用及星云源区及通过次生母体的作用过程阐释星云和前星云的记录。本文概述了早期太阳系内从星云到陨石的演化过程。依据这些资料,对早期太阳系所经历的多种核合成的输入、瞬时加热事件与星云动力学有一些新的认识,以及认识到小星子和行星体系的演化比以前预期的更快速。 相似文献
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Isotopic heterogeneity within the solar nebula has been a long-standing issue. Studies on primitive chondrites and chondrite components for Ba, Sm, Nd, Mo, Ru, Hf, Ti, and Os yielded conflicting results, with some studies suggesting large-scale heterogeneity. Low-grade enstatite and Rumuruti chondrites represent the most extreme ends of the chondrite meteorites in terms of oxidation state, and might thus also present extremes if there is significant isotopic heterogeneity across the region of chondrite formation. Osmium is an ideal tracer because of its multiple isotopes generated by a combination of p-, r-, and s-process and, as a refractory element; it records the earliest stages of condensation.Some grade 3-4 enstatite and Rumuruti chondrites show similar deficits of s-process components as revealed by high-precision Os isotope studies in some low-grade carbonaceous and ordinary chondrites. Enstatite chondrites of grades 5-6 have Os isotopic composition identical within error to terrestrial and solar composition. This supports the view of digestion-resistant presolar grains, most likely SiC, as the major carrier of these anomalies. Destruction of presolar grains during parent body processing, which all high-grade enstatite chondrites, but also some low-grade chondrites seemingly underwent, makes the isotopically anomalous Os accessible for analysis. The magnitude of the anomalies is consistent with the presence of a few ppm of presolar SiC with a highly unusual isotopic composition, produced in a different stellar environment like asymptotic giant branch stars (AGB) and injected into the solar nebula. The presence of similar Os isotopic anomalies throughout all major chondrite groups implies that carriers of Os isotopic anomalies were homogeneously distributed in the solar nebula, at least across the formation region of chondrites. 相似文献
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The distribution of the major elements between vapor and solid has been calculated for a cooling gas of cosmic composition. The assumption is made that high temperature condensates remain in equilibrium with the vapor, affecting the temperatures of appearance of successively less refractory phases. The model suggests that the major textural features and mineralogical composition of the Ca, Al-rich inclusions in the C3 chondrites were produced during condensation in the nebula characterized by slight departures from chemical equilibrium due to incomplete reaction of high temperature condensates. Fractionation of such a phase assemblage is sufficient to produce part of the lithophile element depletion of the ordinary chondrites relative to the cosmic abundances. 相似文献
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侯渭 《中国地球化学学报》1996,15(2):100-104
The data available show that some Antarctic carbonaceous chondrites are similar to Cl meteorites.Tehy contain a lot of phyllosilicate aggregates and the oxygen isotopic composition of the whole-rock samples is approximate to that of C1 chondrites,so they are named after quasi-C1(Q-C1)chondrites Unlike Cl metcorites,the Q-Cl chondites possess chondrule structrue,and the compositions of hih 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 to C group chondrites.It is inferred that the Q-C1 chondrites could be formed at the edges far from the equator in the whole asteroid region of the solar nebular disk.where the nebula was lower in density and the condensates were lower in accretion velocity,so that the hydration of chon drules and matrix occurred during the late stage of nebular condensation.The discovery of the Q-Cl chondrites and the fact that the earth and other terrestrial planets contain water indicate that at the edges far from the equator in the terrestrial reigion of the solar nebular disk,a large amount of water was incorporated into the lattice of minerals in the condensates as a result of hydration during nebular condensation,and then found its way into the interior parts of the Earth and other terrestrial planets due to accretion. 相似文献
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Lawrence Grossman 《Geochimica et cosmochimica acta》1973,37(5):1119-1140
The condensation temperatures are calculated for a number of refractory trace metals from a gas of solar composition at 10?3 and 10?4 atm. total pressure. Instrumental neutron activation analysis of Ca-Al-rich inclusions in the Allende carbonaceous chondrite reveals enrichments of 22.8 ± 2.2 in the concentrations of Ir, Sc and the rare earths relative to Cl chondrites. Such enrichments cannot be due to magmatic differentiation processes because of the marked differences in chemical behavior between Ir and Sc, exhibited by their distributions in terrestrial igneous rocks and meteorites. All of these elements should have condensed from a cooling gas of solar composition above or within the range of condensation temperatures of the major mineral phases of the inclusions, which suggests that these inclusions are high-temperature condensates from the primitive solar nebula. Gas-dust fractionation of these materials may have been responsible for the depletion of refractory elements in the ordinary and enstatite chondrites relative to the carbonaceous chondrites. 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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Wetherill GW 《Geochimica et cosmochimica acta》1994,58(20):4513-4520
Earlier work on the simultaneous accumulation of the asteroid belt and the terrestrial planets is extended to investigate the relative contribution to the final planets made by material from different heliocentric distances. As before, stochastic variations intrinsic to the accumulation processes lead to a variety of final planetary configurations, but include systems having a number of features similar to our solar system. Fifty-nine new simulations are presented, from which thirteen are selected as more similar to our solar system than the others. It is found that the concept of "local feeding zones" for each final terrestrial planet has no validity for this model. Instead, the final terrestrial planets receive major contributions from bodies ranging from 0.5 to at least 2.5 AU, and often to greater distances. Nevertheless, there is a correlation between the final heliocentric distance of a planet and its average provenance. Together with the effect of stochastic fluctuations, this permits variation in the composition of the terrestrial planets, such as the difference in the decompressed density of Earth and Mars. Biologically important light elements, derived from the asteroidal region, are likely to have been significant constituents of the Earth during its formation. 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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Primordial compositions of refractory inclusions 总被引：1，自引：0，他引：1
L. Grossman S.B. Simon M.H. Thiemens R.W. Williams T. Ding R.N. Clayton T.K. Mayeda 《Geochimica et cosmochimica acta》2008,72(12):3001-3021
Bulk chemical and O-, Mg- and Si-isotopic compositions were measured for each of 17 Types A and B refractory inclusions from CV3 chondrites. After bulk chemical compositions were corrected for non-representative sampling in the laboratory, the Mg- and Si-isotopic compositions of each inclusion were used to calculate its original chemical composition assuming that the heavy-isotope enrichments of these elements are due to Rayleigh fractionation that accompanied their evaporation from CMAS liquids. The resulting pre-evaporation chemical compositions are consistent with those predicted by equilibrium thermodynamic calculations for high-temperature nebular condensates, but only if different inclusions condensed from nebular regions that ranged in total pressure from 10−6 to 10−1 bar, regardless of whether they formed in a system of solar composition or in one enriched in dust of ordinary chondrite composition relative to gas by a factor of 10 compared to solar composition. This is similar to the range of total pressures predicted by dynamic models of the solar nebula for regions whose temperatures are in the range of silicate condensation temperatures. Alternatively, if departure from equilibrium condensation and/or non-representative sampling of condensates in the nebula occurred, the inferred range of total pressure could be smaller. Simple kinetic modeling of evaporation successfully reproduces observed chemical compositions of most inclusions from their inferred pre-evaporation compositions, suggesting that closed-system isotopic exchange processes did not have a significant effect on their isotopic compositions. Comparison of pre-evaporation compositions with observed ones indicates that 80% of the enrichment in refractory CaO + Al2O3 relative to more volatile MgO + SiO2 is due to initial condensation and 20% due to subsequent evaporation for both Types A and B inclusions. 相似文献