富钙长石-橄榄石包体与其他部分典型包体W-L边的成因

球粒陨石中的富Ca、Al包体(简称CAI)形成于星云演化的最初始阶段,保存了大量星云形成和演化的各种信息。研究认为,包体的成因主要包括星云直接凝聚和熔融结晶,少部分甚至经历过高温蒸发过程。部分CAI最外层具有由一种或几种矿物组成的Warking-Lovering边(简称为W-L边),CAI和其W-L边对于认识早期星云环境和界定CAI的形成时间等均具有重要意义。目前,对于W-L边的形成过程研究并不深入,且一直存在争议。本文主要介绍了三个典型包体:C#1(富钙长石-橄榄石包体)、GRV 022459-2RI5(A型包体)和GRV 021579-3RI5(富尖晶石球粒状包体)及其W-L边的矿物岩石学和氧同位素组成特征。C#1包体明显经历过熔融结晶过程,W-L边氧同位素组成具有与包体内部矿物相似的富~(16)O同位素特征,表明W-L边的成因与包体的形成过程密切相关,形成于同一富~(16)O同位素组成区域,且W-L边属于包体熔融结晶过程后期的产物。矿物岩石学特征表明,GRV 022459-2RI5属于星云直接凝聚形成,其W-L边为包体形成过程最晚期星云凝聚产物。GRV021579-3RI5经历过熔融结晶过程,其W-L边为包体结晶最后阶段的产物。     

富钙长石-橄榄石型包体与典型富Ca,Al包体的矿物岩石学特征对比研究

本文研究了2个富钙长石-橄榄石型包体和2个富黄长石-尖晶石型和富尖晶石-辉石型包体（分别来自宁强和南极格罗夫山碳质球粒陨石）的矿物岩石学特征,并对它们进行了对比。富钙长石-橄榄石型包体的矿物模式组成具有富橄榄石和缺失黄长石的特征,其可能是球粒和典型难熔包体之间的中间产物,是认识它们之间相互关系的钥匙。矿物岩石学特征表明富黄长石-尖晶石型和富尖晶石-辉石型包体可能是星云直接凝聚的产物,而富钙长石-橄榄石型包体经历过熔融结晶过程。富钙长石-橄榄石型包体的初始物质可能是富Al的球粒或含难熔组分的蠕虫状橄榄石集合体。矿物化学组成对比研究发现,GRV 022459-RI6中的尖晶石具有最富FeO的特征,表明包体的蚀变可能发生在高氧逸度的星云环境。     

太阳星云凝聚过程的岩石学模型：（1）球粒陨石的凝聚成因

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。     

富橄榄石的富Ca,Al组分集合体的矿物岩石学特征及对比研究

富Ca,Al包体、球粒和蠕虫状橄榄石集合体都是早期星云事件的产物。本文探讨了4个富橄榄石的富Ca,Al组分集合体的矿物岩石学特征,并对它们进行了对比。矿物岩石学特征表明含橄榄石边的富尖晶石—辉石型包体和富Ca,Al组分蠕虫状橄榄石集合体都属于星云直接凝聚的产物,而富钙长石—橄榄石型包体(POI)和富Ca,Al组分球粒经历过熔融结晶过程。矿物模式组成表明POI包体和富Ca,Al组分球粒可能是认识典型富Ca,Al包体与球粒之间相互关系的钥匙。蠕虫状橄榄石集合体GRV022459-2C1中尖晶石普遍具有高的FeO含量,表明其蚀变发生于高氧逸度的星云环境。球粒与粗粒富Ca,Al包体可能属于同一热事件的产物,粗粒富Ca,Al包体形成于富Ca,Al矿物富集的区域,Mg,Fe质硅酸盐球粒形成于富Ca,Al矿物缺失的区域,POI包体和富Ca,Al组分球粒可能形成于上述两个区域之间的过渡区域。     

肇东和亳县陨石中的黑包体及其成因意义

肇东、毫县陨石中的黑包体在总体成分、形状、大小上与陨石球粒相似,但两者的内部结构以及矿物组合不同。黑包体中矿物呈密堆状,主要由细粒橄榄石以及其它硅酸盐微晶组成,不含火成玻璃等特点表明黑包体未经历过熔融,它们可能是形成球粒的毛坯。因此认为球粒的形成有三个阶段:星云凝聚形成尘粒—尘粒吸积形成黑包体—黑包体熔融形成球粒。     

球粒陨石中富Al球粒的氧同位素组成与形成演化过程

球粒陨石中的富Ca、Al包体(简称CAIs)主要由一些富Ca、Al的硅酸盐和氧化物(如尖晶石和黄长石等)组成,是目前已知的太阳系最古老的固体物质(4567.2±0.6 Ma;4567.30±0.16 Ma);球粒的矿物组成以镁铁质硅酸盐(如橄榄石和低Ca辉石等)为主,明显经历过熔融结晶过程.CAIs及其构成矿物具有最富...     

陨石含水矿物成因评述和地球水来源的探讨

简要介绍了球粒陨石中含水矿物的种类和主要特点，根据陨石中含水矿物与无水矿物，有机质的关系，太阳星云凝聚模型中有关水蒸汽与无水矿物反应的理论，以及有关的同位素资料的综合分析，推断形成含水矿物的水化作用是太阳星云凝聚作用的一个阶段，通过不同类型球粒陨石氧同位素组成和含水矿物数量的比较，论证了太阳星云盘中发生水作用的范围，从而对地球水的来源进行了讨论。     

清镇顽火辉石球粒陨石的矿物学特征及其成因

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。     

南极 GRV 021788橄辉无球粒陨石的岩石学和矿物学特征

橄辉无球粒陨石是一类特殊的无球粒陨石,既具有高度分异的火成特征,又具有原始球粒陨石的特征。南极格罗夫山GRV021788陨石由橄榄石、辉石以及少量的富碳基质、不透明矿物组成,具有橄辉无球粒陨石典型的岩相学和矿物学特征,包括橄榄石晶体三线共点的接触和富镁还原边等。GRV021788的主要矿物的化学成分为:橄榄石Fa23.2～Fa1.5,易变辉石Fs21.2Wo10.6～Fs18.7Wo10.7。橄榄石颗粒有明显的反环带结构,而易变辉石的反环带则不明显。黑色填隙基质富碳,含金刚石和石墨。岩石学和矿物化学特征表明GRV021788是一橄辉无球粒陨石,属单矿(monomict)Ⅰ类(Fa23.2～Fs20.4)橄辉无球粒陨石。陨石的形成机制与多阶段部分熔融-堆积模式较为一致。     

GRV 13100顽火辉石球粒陨石中金属硫化物特征与成因

顽火辉石球粒陨石中的大量金属硫化物形成于早期极还原的太阳星云条件。GRV13100是一块发现于南极格罗夫山的顽火辉石球粒陨石,不透明矿物包括陨硫铁、陨硫铬铁矿、陨硫镁矿、陨硫钙矿、含硅铁纹石、陨磷铁矿、硅磷镍矿等金属硫化物和磷化物,总丰度达21%,经历了一定程度的热变质。通过对其岩石学和矿物化学特征研究,并和其它顽火辉球粒陨石进行对比分析,结果表明:(1)陨硫镁矿中FeS含量可以反映母体变质温度,GRV 13100中大部分陨硫镁矿变质温度为200℃～300℃,个别经历了400℃～800℃的高温,可能为外来吸入成因,或者代表了原始星云的凝聚或结晶温度;(2)陨硫镁矿形成于太阳星云的直接凝聚,并在橄榄石和顽火辉石冷凝结晶之后形成;(3)陨硫铁的成因分为原生和次生两种,原生的陨硫铁由太阳星云直接凝聚而成,次生的陨硫铁是在后期热变质过程中由铁镍金属经过硫化作用或者由陨硫镁矿分解而形成;(4)硅磷镍矿可能来自含硅铁纹石的出溶。本论文的研究工作为太阳系早期高度还原星云演化及其后期热变质提供了约束。     

Ca-, Al-rich Inclusions in Three New Carbonaceous Chondrites from the Grove Mountains, Antarctica: New Evidence for a Similar Origin of the Objects in Various Groups of Chondrites

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     

“Fluffy” Type A Ca-, Al-rich inclusions in the Allende meteorite

Allende “fluffy” Type A's (FTA's) are a distinct sub-group of Ca-, Al-rich inclusions whose primary mineral assemblage consists of Al-rich melilite (Åk 0–33), spinel that is commonly very V-rich, perovskite and, frequently, hibonite. Some contain relatively coarse-grained melilite (up to 1.5 mm) that is intensely kink-banded and commonly reversely-zoned, hibonite and V-rich spinel. Others contain much finer-grained and strain-free melilite (?50 μm) and have not been found to contain hibonite or V-rich spinel. Some FTA's contain both coarser- and finer-grained melilite and textural relationships indicate that the latter is replacing the former. FTA's are characterized by extremely irregular shapes and 60–75 volume per cent of fine-grained, secondary alteration products. Many are aggregates of innumerable nodules, each of which is surrounded by a Wark-Lovering-type rim sequence. These nodules are frequently separated from one another by matrix-like clastic rim material. Other FTA's do not have nodular structure. Structural and mineralogical characteristics of their Wark-Lovering rims suggest that FTA's did not achieve their shapes by deformation of a liquid or a hot, plastic solid. In contrast to those in Type B inclusions, formation of reverse zoning in the coarser-grained melilite crystals in FTA's cannot be understood in terms of crystallization from a liquid but are readily explainable by condensation from a solar nebular gas during a period of falling pressure. Further evidence against a liquid origin is the wide range of spinel compositions within individual coarser-grained FTA's. The fact that the reversely-zoned melilite crystals cannot have been produced in any kind of sublimation or distillation process precludes formation of these inclusions as volatilization residues. FTA's are aggregates in some of which are preserved vapor-solid condensate grains that formed at high temperature in the solar nebula.     

Formation of disk- and bowl-shaped igneous Ca,Al-rich inclusions: Constraints from their morphology,textures, mineralogy and modelling

Calcium-aluminum-rich inclusions (CAIs) are the oldest Solar System solids dated that formed by evaporation, condensation, aggregation and, sometimes, melting processes near the protoSun, and were subsequently dispersed throughout the protoplanetary disk by still poorly-understood mechanism(s). Here we report on the discovery of disk- and bowl-shaped centimeter-sized igneous CAIs in CV (Vigarano type) carbonaceous chondrites. Igneous CAIs of these shapes are not expected for crystallization of melt droplets in a low gravity field of the protoplanetary disk. We have tested several models for the formation of disk- and bowl-shaped igneous CAIs including: collision, aerodynamic deformation and shock flattening. We conclude that these CAIs resulted from aerodynamic deformation of CAI-like melt droplets and propose the following multistage formation scenario: (1) nearly complete melting and acceleration of CAIs at <30 km/s in the CAI-forming region having approximately solar dust/gas ratio; (2) aerodynamic deformation, ablation, deceleration, solidification at ∼30–40 K/min, Wark-Lovering rims formation, and deceleration of the CAIs entering a dust-rich inner disk wall; (3) radial drift of the solidified deformed CAIs towards the Sun; (4) heating and partial melting of the deformed CAIs by solar radiation that preserve their morphology; (5) cooling and crystallization of CAIs at ∼2 K/h; (5) radial transport of CAIs from their formation region to the outer disk.     

大厂锡矿床黑色包裹体成因分析及容矿围岩的古地温研究

在大厂长坡-铜坑矿床,锡石中普遍存在具有代表性的2类包裹体:黑色包裹体和气-液两相的流体包裹体。文章通过对包裹体结构形态和理论分析,证明黑色包裹体是原生流体包裹体在内压超高(overpressured)条件下形成的。通过牙形石色温指数(CAI)及表面残余结构的研究,获得了容矿岩石的古地温为300～650℃,与前人通过气-液两相包裹体获得的矿化温度(240～540℃)高度吻合,说明容矿围岩的受热事件与同期矿化事件,其热源具有同源性,可能来自矿床下伏的燕山期花岗岩。层状主矿体锡石中原生的流体包裹体正是在这期事件的影响下,变成了黑色包裹体。这些研究证明,大厂锡矿至少有早、晚2期成矿作用。黑色包裹体的发现和古地温的恢复,为层状主矿体是在海底热液喷流沉积成因的认识提供了关键证据。     

Alteration of Al-rich inclusions inside amoeboid olivine aggregates in the Allende meteorite

Lightly altered Al-rich inclusions in amoeboid olivine aggregates have cores containing primary melilite + fassaite + spinel + perovskite and no secondary alteration products. In moderately altered inclusions, whose cores now contain only fassaite + spinel + perovskite, melilite was replaced by a fine-grained mixture of grossular + anorthite + feldspathoids and perovskite was partially replaced by ilmenite. In heavily altered inclusions, fassaite has been replaced by a mixture of phyllosilicates + ilmenite and the remaining primary phases are spinel ± perovskite. In very heavily altered inclusions, no primary phases remain, the spinel having reacted to form either phyllosilicates or a mixture of olivine + feldspathoids. This sequence of alteration reactions may reflect successively lower solar nebular equilibration temperatures. During alteration, SiO₂, Na₂O, K₂O, FeO, Cr₂O₃, H₂O and Cl were introduced into the inclusions and CaO was lost. MgO may have been lost during the melilite reaction and added during formation of phyllosilicates. Electron microprobe analyses indicate that the phyllosilicates are a mixture of Na-rich phlogopite and chlorite or Alrich serpentine. Thermodynamic calculations suggest that, at a solar nebular water fugacity of 10⁻⁶, Na-rich phlogopite could have formed from fassaite at ~470 K and chlorite from Na-rich phlogopite at ~328 K. Olivine mantling Al-rich inclusions is not serpentinized, suggesting that these objects stopped equilibrating with the nebular gas above 274 K.     

The nature and origin of type B1 and B2 CaAl-rich inclusions in the Allende meteorite

The Type B CaAl-rich inclusions in the Allende carbonaceous chondrite form a continuous range from the mineralogically concentrically zoned B1 subtype to the unzoned B2 subtype. These subtypes differ in (i) structure, texture, grain size and shape, (ii) mineralogical proportions and compositions, (iii) accessory mineralogy, (iv) relative abundance of spinel framboids, (v) rim layering, (vi) major element chemistry, and (vii) degree of secondary alteration.These differences, together with observations on the crystallization of synthetic melts, suggest that the B1 inclusions crystallised relatively rapidly from molten parental material while B2 types crystallised relatively slowly close to the solidus from material that had not been completely melted.The same data are used to construct an evaporative residue model for the origin of the parental Type B materials. In the model, dust in the protosolar nebula was heated with removal of more volatile elements, leaving completely melted (Type B1) residues at the highest temperatures and incompletely melted, less highly evaporated (Type B2) residues at lower temperatures.     

湖北宜昌王家湾五峰组顶部Chondrites的发现及其环境意义

:本文报道了湖北宜昌王家湾剖面五峰组笔石页岩段观音桥层发现的遗迹化石Chondrites的分布及其生态特点.结合生物相和同期上扬子海盆相对海平面的变化,分析了盆地水体底域在缺氧-富氧转折时期的古氧相变化特征:指出五峰组笔石页岩段上部地层沉积底域为典型的缺氧环境,在其与上覆观音桥段之间的沉积转换面附近发生了从无氧到有氧的转变,观音桥段中Hirnantia动物群繁盛于富氧的海底环境.     

Ca,Al-rich inclusions, amoeboid olivine aggregates, and Al-rich chondrules from the unique carbonaceous chondrite Acfer 094: I. mineralogy and petrology

Based on their mineralogy and petrography, ∼200 refractory inclusions studied in the unique carbonaceous chondrite, Acfer 094, can be divided into corundum-rich (0.5%), hibonite-rich (1.1%), grossite-rich (8.5%), compact and fluffy Type A (spinel-melilite-rich, 50.3%), pyroxene-anorthite-rich (7.4%), and Type C (pyroxene-anorthite-rich with igneous textures, 1.6%) Ca,Al-rich inclusions (CAIs), pyroxene-hibonite spherules (0.5%), and amoeboid olivine aggregates (AOAs, 30.2%). Melilite in some CAIs is replaced by spinel and Al-diopside and/or by anorthite, whereas spinel-pyroxene assemblages in CAIs and AOAs appear to be replaced by anorthite. Forsterite grains in several AOAs are replaced by low-Ca pyroxene. None of the CAIs or AOAs show evidence for Fe-alkali metasomatic or aqueous alteration. The mineralogy, textures, and bulk chemistry of most Acfer 094 refractory inclusions are consistent with their origin by gas-solid condensation and may reflect continuous interaction with SiO and Mg of the cooling nebula gas. It appears that only a few CAIs experienced subsequent melting. The Al-rich chondrules (ARCs; >10 wt% bulk Al₂O₃) consist of forsteritic olivine and low-Ca pyroxene phenocrysts, pigeonite, augite, anorthitic plagioclase, ± spinel, FeNi-metal, and crystalline mesostasis composed of plagioclase, augite and a silica phase. Most ARCs are spherical and mineralogically uniform, but some are irregular in shape and heterogeneous in mineralogy, with distinct ferromagnesian and aluminous domains. The ferromagnesian domains tend to form chondrule mantles, and are dominated by low-Ca pyroxene and forsteritic olivine, anorthitic mesostasis, and Fe,Ni-metal nodules. The aluminous domains are dominated by anorthite, high-Ca pyroxene and spinel, occasionally with inclusions of perovskite; have no or little FeNi-metal; and tend to form cores of the heterogeneous chondrules. The cores are enriched in bulk Ca and Al, and apparently formed from melting of CAI-like precursor material that did not mix completely with adjacent ferromagnesian melt. The inferred presence of CAI-like material among precursors for Al-rich chondrules is in apparent conflict with lack of evidence for melting of CAIs that occur outside chondrules, suggesting that these CAIs were largely absent from chondrule-forming region(s) at the time of chondrule formation. This may imply that there are several populations of CAIs in Acfer 094 and that mixing of “normal” CAIs that occur outside chondrules and chondrules that accreted into the Acfer 094 parent asteroid took place after chondrule formation. Alternatively, there may have been an overlap in the CAI- and chondrule-forming regions, where the least refractory CAIs were mixed with Fe-Mg chondrule precursors. This hypothesis is difficult to reconcile with the lack of evidence of melting of AOAs which represent aggregates of the least refractory CAIs and forsterite grains.