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1.
Reported in this paper are structural and compositional data as the basis for the classification of 35 iron meteorites. The Xingjiang iron meteorite, previously labelled IIIAB, is reclassified as IIIE on the basis of its lower Ga/Ni and Ge/Ni ratios, its wider and swollen kamacite bands and the ubiquitous presence of haxonite, (Fe, Ni)23C. IIICD Dongling appears not to be a new meteorite, but to be paired with Nandan. Four Antarctic iron meteorites IAB Allan Hills A77250, A77263, A77289 and A77290 are classified as paired meteorites based on their similarities in structure, and the concentrations of Cr, Co, Ni, Cu, Ga, Ge, As, Sb, W, Re, Ir and Au. It is found that Cu shares certain properties with Ga and Ge, which makes it an excellent taxonomic parameter. BecauseK Cu is near unity, Cu displays a small range of variation within most magmatic groups (less than a factor of 2.2) and, because of its high volatility, large variations can be noticed among groups.  相似文献   

2.
We have investigated the partitioning of Ir. Ge, Ga, W, Cr, Au, P, and Ni between solid metal and metallic liquid as a function of temperature and S-concentration of the metallic liquid. Partition coefficients for siderophile elements such as Ir, W, Ga and Ge increase by factors of 10–100 as the Sconcentration of the metallic liquid increases from 0–30 wt%. Partition coefficients for other siderophile elements such as Ni, Au and P increase by only factors of 2–3. In contrast, partition coefficients for the more chalcophile element Cr decrease. These experimentally-determined partition coefficients have been used in conjunction with a fractional crystallization model to reproduce the geochemical behavior of Ni, P, Au and Ir during the magmatic evolution of groups IIAB, IIIAB, IVA and IVB iron meteorites. The mean S-concentration for each group increases in the order IVB, IVA, IIIAB, IIAB, in accord with cosmochemical prediction. However, we are unable to reproduce the geochemical behavior of Ge, Ga, W and Cr in an internally consistent way. We conclude that the magmatic histories of these iron meteorite groups are more complex than has been generally assumed.  相似文献   

3.
Total N has been measured in a number of meteorites by neutron activation analysis using the reaction N14(n, p)C14. From each meteorite a number of chips have been analysed to investigate the variation of N contents in a sample. Many meteorites are found to contain a heterogeneous distribution of N. Eighteen chondrites, mostly of the classes C3, H4, H5, L4, L5, L6 and LL6, and six achondrites are found to have average N contents of 10–45 ppm. These do not show any clear-cut dependence of N on petrological group. However, the inherent heterogeneity or the fact that from most meteorite classes only single falls were studied might be responsible for this lack of correlation. In Cold Bokkeveld (C2) N is high (420 ppm). Unlike C, N content of ureilites is low (26 ppm). Nitrogen is enriched in the non-magnetic as compared to the magnetic fractions in H-group chondrites. Analyses of sieved Bjurböle phases show no enrichment of N in finer matrix material, nor any depletion in chondrules. In two gas-rich meteorites, Kapoeta and Assam, there is no excess N in the dark phases. Nine iron meteorites and three mesosiderites were analysed. Twenty analyses of Canyon Diablo and seven of Odessa establish a very heterogeneous N distribution in these meteorites.  相似文献   

4.
Pb isotopic compositions and U-Pb abundances were determined in the metal phase of six iron meteorites: Canyon Diablo IA, Toluca IA, Odessa IA, Youndegin IA, Deport IA and Mundrabilla An. Prior to complete dissolution, samples were subjected to a series of leachings and partial dissolutions. Isotopic compositions and abundances of the etched Pb indicate a contamination by terrestrial Pb which is attributable to previous cutting of the meteorite. Pb isotopic compositions measured in the decontaminated samples are identical within 0.2% and essentially confirm the primordial Pb value defined by Tatsumotoet al. (1973). These data invalidate more radiogenic Pb isotopic compositions published for iron meteorites, which are the result of terrestrial Pb contamination introduced mainly by analytical procedure. Our results support the idea of a solar nebula which was isotopically homogeneous for Pb 4.55 Ga ago. The new upper limit for U-abundance in iron meteorites, 0.001 ppb, is in agreement with its expected thermodynamic solubility in the metal phase.  相似文献   

5.
混合酸比例对ICP-MS/OES测定地球化学样品中多元素的影响   总被引：1，自引：0，他引：1  
罗艳  杨侨 《岩矿测试》2017,36(6):587-593
应用电感耦合等离子体质谱/发射光谱仪(ICP-MS/OES)测定地球化学样品中的多元素时,通常采用混合酸(盐酸-硝酸-氢氟酸-高氯酸)分解试样,但不同比例的混合酸对试样的分解效果影响极大,导致测试结果中经常出现铬、锰、铁、铝、钛及部分稀土元素测定结果偏低、精密度不理想的情况。本文通过改变混合酸中各类酸的混合比例,采用逆王水-氢氟酸-高氯酸分解试样,逆王水提取,使上述元素获得了较为理想的分解效果,特别是这些元素含量较高的样品分解效果的改善尤为显著。实验证明:当取样量为0.100 g时,采用8 mL逆王水、6 mL氢氟酸、3 mL高氯酸分解试样,8 mL逆王水提取,用国家一级标准物质进行验证,测试结果的相对标准偏差(n=6)为0.34%~4.02%,本方法精密度和准确度均满足地质实验室质量管理规范要求,可快速、准确、批量测定地球化学样品中的多元素。  相似文献   

6.
Magmatic iron meteorites are thought to be samples of the central metallic cores of asteroid-sized parent bodies. Sulfur is believed to have been an important constituent of these parental cores, but due to the low solubility of S in solid metal, initial S-contents for the magmatic groups cannot be determined through direct measurements of the iron meteorites. However, experimental solid metal-liquid metal partition coefficients show a strong dependence on the S-content of the metallic liquid. Thus, by using the experimental partition coefficients to model the fractional crystallization trends within magmatic iron meteorite groups, the S-contents of the parental cores can be indirectly estimated. Modeling the Au, Ga, Ge, and Ir fractionations in four of the largest magmatic iron meteorite groups leads to best estimates for the S-contents of the parental cores of 12 ± 1.5 wt% for the IIIAB group, 17 ± 1.5 wt% for the IIAB group, and 1 ± 1 wt% for the IVB group. The IVA elemental fractionations are not adequately fit by a simple fractional crystallization model with a unique initial S-content. These S-content estimates are much higher than those recently inferred from crystallization models involving trapped melt. The discrepancy is due largely to the different partition coefficients that are used by the two models. When only partition coefficients that are consistent with the experimental data are used, the trapped melt model, and the low S-contents it advocates, cannot match the Ge and Ir fractionations that are observed in IIIAB iron meteorites.  相似文献   

7.
Twenty-one iron meteorites with Ge contents below 1 μg/g, including nine belonging to groups IIIF and IVB, have been analyzed by instrumental neutron activation analysis (INAA) for the elements Co, Cr, As, Au, Re, Ir and W. Groups IIIF and IVB show positive correlations of Au, As and Co (IIIF only) with published Ni analyses, and negative correlations of Ir, Re, Cr (IVB only) and W (IIIF only) with Ni. On element-Ni plots, the gradients of the least squares lines are similar to those of many other groups, excluding IAB and IIICD. With the inclusion of a new member, Klamath Falls, group IIIF has the widest range of Au, As and Co contents of any group and the steepest gradients on plots of these elements against Ni. It is likely that these trends in groups IIIF and IVB were produced by fractionation of elements between solid and liquid metal, probably during fractional crystallization.It has been suggested that some of the 15 irons with <l μg/g Ge which lie outside the groups might be related. However, the INAA data indicate that no two are as strongly related as two group members. These low-Ge irons and the members of groups IIIF, IVA and IVB tend to have low concentrations of As, Au and P, low CoNi ratios and high Cr contents. The depletion of the more volatile elements probably results from incomplete condensation into the metal from the solar nebula.The structures of low-Ge irons generally reflect fast cooling rates (20–2000 K Myr?1). When data for all iron meteorites are plotted on a logarithmic graph of cooling rate against Ge concentration and results for related irons are averaged, there is a significant negative correlation. This suggests that metal grains which inefficiently condensed Ge and other volatile elements tended to accrete into small parent bodies.  相似文献   

8.
Samples of bulk meteorites show only mass-dependent fractionation of silicon isotopes. No isotopic anomalies were found. The variation of the ratios 29Si/28Si and 30Si/28Si over the meteorite classes is small; 1%. per mass unit difference. The average Si isotopic composition for each class of meteorites is identical, within analytical uncertainties. This is quite unlike O, whose anomalous isotopic abundances in bulk samples differentiate among the classes of meteorites. The overlapping abundance ranges of Si isotopes among many classes of meteorites suggest closed-system behavior for this element prior to meteorite accretion and allow calculation of an average solar system Si isotope composition.  相似文献   

9.
Based on structural observations and the concentrations of Cr, Co, Ni, Cu, Ga, Ge, As, Sb, Re, Ir, and Au by neutron-activation analysis we have classified 14 Chinese iron meteorites. Thirteen are members of the large groups IAB, IIICD, IIIAB and IVA. Leshan is an ungrouped iron meteorite that falls within the IIE field on some element-Ni diagrams, but is distinctly outside this field on plots of Cu, W, and Ir vs. Ni; it is very similar in composition to Techado, another ungrouped iron. The high Cu content of Leshan in consistent with other evidence indicating that Cu is a valuable parameter for classifying iron meteorites. IIICD Dongling appears not to be a new meteorite, but to be paired with Nantan; Dongling was recovered about 50 km from the location of the Nantan shower. In view of the fact that Yongning is highly oxidized, we assign it to group IAB but cannot rule out IIICD. IVA-An Longchang has many characteristics of IVA irons, but has been remelted, probably in a terrestrial setting. Five irons belong to group IVA, a remarkably large number. Three are identical in composition, and we suspect that the two from Hubei, Guanghua and Huangling, are paired. Thus this set of 14 irons includes 12 independent falls.  相似文献   

10.
胡顺峰  王霞  郭合颜  金伟 《岩矿测试》2011,30(4):465-468
选用王水、氢氟酸、高氯酸、盐酸对红土镍矿石样品进行溶样试验,结果表明采用王水溶解,氢氟酸助溶,高氯酸冒烟除去氢氟酸的溶样方法较好;用盐酸溶解盐类,电感耦合等离子体发射光谱法测定溶液中镍、铬、镁、铝、钴元素,对目标元素进行了光谱干扰考察,选择了合适的分析谱线,结果表明铁会使目标元素谱线背景强度增高,采用在混合标准溶液中加入与样品中含量相当的铁可以消除基体干扰;除铬元素外其他目标元素加标回收率在96.83%～105.23%,相对标准偏差小于3.3%。建立的方法应用于标准样品分析,除铬元素外的其他元素测定值与标准值吻合较好。铬元素回收率较低,有待进一步研究。  相似文献   

11.
The speciation of metals in environmental samples is a critical factor in assessing the potential environmental impacts, before their disposal. The distribution and speciation of toxic heavy metals in plating wastewater residues and sludge was investigated for four samples using sequential extraction method. Tessier method was used to fractionate the metal content into exchangeable, acid extractable, reducible and oxidizable fractions. Residual and total metal contents were determined in aqua regia digest. The extracts were analysed for metals using inductively coupled plasma -atomic emission spectrometry. The bioavailable fraction (exchangeable and acid extractable fractions) is comprised less than the other forms. The oxidisable and reducible forms are dominants for all the four samples studied. The major metal constitute in the samples is iron, the wastewater residue contains (12.3 and 7.4 g/Kg respectively on dry basis) and the sludge contains (31.5 and 41.6 g /Kg) respectively. Cr concentration is higher in wastewater residue of second electroplating industry. The descending order of the average total metal contents for these four samples were Fe > Cr > Sn > Zn >Cu > Ni > Mn > Pb > Cd > Ag. Based on the average of absolute values for the four samples the highest bioavailability order of metals is Cr (39 %) in wastewater residues and Zn (32 %) in sludge samples. Metal recovery was good, with < 10 % difference between the total metal recovered through the extractant steps and the total metal determined using aqua regia extract.  相似文献   

12.
李刚  曹小燕 《岩矿测试》2008,27(3):197-200
采用HF-HClO4-HNO3分解样品,8 mol/L HNO3提取剂,外标法校准,电感耦合等离子体质谱法同时测定地球化学样品中锗和镉。选择103Rh为内标,确定了最佳仪器参数,研究了Zn、Zr、Sn、Ce、Nd、Sm对Ge和Cd的干扰,试验选择质量数74Ge和114Cd作为测定同位素,采用数学公式校正法校正了来自Nd和Sm的二次电离离子对Ge的干扰、Sn对Cd的同质异位素干扰。方法检出限（10s）分别为Ge 30 ng/L、Cd 15 ng/L,精密度（RSD,n=15）为Ge 1.35%、Cd 1.47%。对多种国家一级标准物质进行分析验证,结果与标准值相符。方法适用于地质样品中微量锗和镉的测定。  相似文献   

13.
The nickel–iron meteorite of Morasko shows isolated inclusions of troilite in the bulk mass of a Fe,Ni-alloy. During a segregation of the FeS phase chalcophile trace elements were collected from the melt. The solidification of the Fe,Ni-phase occurred probably later, incorporating thereby mainly siderophile trace elements. To prove this general assumption selected trace elements were determined and reveal in the two phases of the present meteorite a characteristic distribution pattern. The meteorite of Morasko is in close conformity to the iron meteorite group IAB with rounded dark FeS inclusions.  相似文献   

14.
Rhenium and osmium in organic-rich sedimentary rocks are dominantly hydrogenous, but any nonhydrogenous component will influence the accuracy and precision of the Re–Os date obtained. To minimize the influence of any nonhydrogenous Re and Os, we evaluate analysis of isolated organic matter from the whole rock, together with whole rock analysis using a CrO3–H2SO4 digestion medium instead of inverse aqua regia, for a black shale unit of the Exshaw Formation, Canada. This unit previously returned a whole rock Re–Os date of 358±10 Ma (Model 3) [Geochim. Cosmochim. Acta (2002)] using inverse aqua regia dissolution. Organic matter isolated from the whole rock matrix using the HF–BF3 technique [Org. Geochem. 20 (1993) 249] yields scattered data and a Re–Os date of 449±220 Ma (Model 3, MSWD=616). The organic matter analyses show similar 187Os/188Os values, but significantly lower 187Re/188Os values in comparison to the whole rock analyses. We show that the Re–Os systematics of organic matter are altered during chemical isolation, and as such we suggest that the HF–BF3 method should not be used for Re–Os analysis of organic matter. Whole rock Re–Os analysis using a CrO3–H2SO4 digestion medium yields significantly better regression analysis compared with the inverse aqua regia method, and the Re–Os data identify two distinct initial 187Os/188Os values for the sample set. Separate regressions of these data yield precise dates [366.1±9.6, MSWD=2.2 and 363.4±5.6 Ma, MSWD=1.6 (Model 3)], which are indistinguishable from the age constraints for this formation (363.4±0.4 Ma, U–Pb monazite). Comparison of the Re–Os dates obtained from aqua regia and CrO3–H2SO4 methods suggests that the former may contain nonhydrogenous Re and Os, whereas the CrO3–H2SO4 method dominantly liberates hydrogenous Re–Os from organic matter, allowing for better stratigraphic age determinations and evaluation of the Os isotope composition of seawater.  相似文献   

15.
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   

16.
We report structural and compositional data leading to the classification of 41 iron meteorites, increasing the number of classified independent iron meteorites to 576. We also obtained data on a new metal-rich mesosiderite and on two new iron masses that are paired with previously studied irons. For the first time in this series we also report concentrations of Cr, Co, Cu, As, Sb, W, Re and Au in each of these 44 meteorites. We determined 7 of these elements (all except Sb) in 30 previously studied ungrouped or unusual irons, and obtained Cu data on 104 irons, 21 pallasites, and 3 meteorite phases previously studied by E. Scott. We show that Cu possesses characteristics well suited to a taxonomic element: a siderophile nature, a large range among all irons, and a low range within magmatic groups. For the first time we report the partial resolution of the C-rich group IIIE from its populous twin group IIIAB on element-Ni diagrams other than Ir-Ni. Cachiyuyal previously classified ungrouped and Armanty (Xinjiang) previously classified IIIAB are reclassified IIIE. Despite the addition of 3 new irons and the reanalysis of 3 previously studied irons the members of the set of 15 ungrouped irons having very low Ga (<3 μg/g) and Ge (<0.7 μg/g) contents remain individualists. The same is generally true for irons having 100 ≤ Ni ≤ 180 mg/g and compositional similarities to IIICD, but A80104 increases the Garden Head trio to a quartet. Algoma is reclassified from ungrouped to IIICD-an and Hassi-Jekna and Magnesia from IIICD to IIICD-an. The metal of Horse Creek and Mount Egerton is compositionally closely related to metal from EH chondrites. We suggest that the P-rich Bellsbank trio irons formed in the IIAB core in topographic lows filled with an immiscible, P-rich second liquid.  相似文献   

17.
Bulk compositions of metallic Fe-Ni from two equilibrated ordinary chondrites, Jilin (H5) and Anlong (H5), and two unequilibrated ones, GRV 9919 (L3) and GRV 021603 (H3), were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The CI-, Co-normalized abundances of siderophile and chalcophile elements of metallic Fe-Ni from the unequilibrated ordinary chondrites correlate with 50% condensation temperatures (i.e., volatility) of the elements. The refractory siderophile elements (i.e., platinum group elements, Re), Au, Ni and Co show a flat pattern (1.01×CI Co-normalized), while moderate elements (As, Cu, Ag, Ga, Ge, Zn) decrease with volatility from 0.63×CI (Co-normalized, As) to 0.05×CI (Co-normalized, Zn). Cr and Mn show deficit relative to the trend, probably due to their main partition in silicates and sulfides (nonmagnetic). Metallic Fe-Ni from the equilibrated ordinary chondrites shows similar patterns, except for strong deficit of Cr, Mn, Ag and Zn. It is indicated that these elements were almost all partitioned into silicates and/or sulfides during thermal metamorphism. The similar deficit of Cr, Mn, Ag and Zn was also found in iron meteorites. Our analyses demonstrate similar behaviors of W and Mo as refractory siderophile elements during condensation of the solar nebula, except for slight depletion of Mo in the L3 and H5 chondrites. The Mo-depletion of metallic Fe-Ni from GRV 9919 (L3) relative to GRV 021603 (H3) could be due to a more oxidizing condition of the former than the latter in the solar nebula. In contrast, the Mo-depletion of the metallic Fe-Ni from the H5 chondrites may reflect partition of Mo from metal to silicates and/or sulfides during thermal metamorphism in the asteroidal body.  相似文献   

18.
本文对南丹IIICD铁陨石的矿物学特征进行了研究,并与同为铁陨石但化学分类不同的阿根廷IAB铁陨石和西伯利亚IIB铁陨石进行了对比,重点探讨了风化作用对铁陨石矿物学特征的影响.首先用偏光显微镜、静水称重、扫描电镜观察了样品的基本矿物学特征和微形貌特征,然后用振动式样品磁强计、X射线衍射与电子探针能谱半定量测试研究了样品的磁学性质、物相和化学组成.研究结果表明,南丹铁陨石在较强的自然风化作用下,光泽变弱为土状光泽,相对密度降低;风化产生的反铁磁性物质会使陨石的磁性下降;另外,样品表面物相组成也发生较大变化,以针铁矿(FeOOH)和磁铁矿(Fe3O4)等铁的次生矿物为主;但风化壳以下的矿物物相及化学成分均未发生明显变化,以Fe、Ni为主的铁纹石、镍纹石物相存在.  相似文献   

19.
王水溶样-氢醌容量法测定碳酸盐地质样品中的金   总被引：1，自引：1，他引：0  
张志刚  刘凯  黄劲  高晶  陈泓  魏晶晶 《岩矿测试》2014,33(2):236-240
应用王水溶样-活性炭富集金-氢醌容量法测定岩石、土壤等一般地质样品中的金时,王水溶样后经布氏漏斗抽滤后剩余的不溶物残渣中金含量小于金总量的4%,通常不计入分析结果。而碳酸盐地质样品经焙烧后在王水溶解过程中因为钙和镁的硅酸盐含量较高,形成了不溶于王水的二氧化硅凝胶及大量钙镁胶状物,包裹和吸附样品溶液中的金,造成分析过程中金的损失。本文将抽滤后的滤液和不溶物残渣分别处理,收集王水分解样品抽滤步骤后的不溶物残渣,用氢氟酸-硫酸除硅,王水溶解测定残渣中的金含量,滤液和残渣两次测试合量为样品中金含量。实验研究了不溶物残渣中的金量、金的来源以及样品中硅钙镁的含量对金测定的影响。结果表明,不溶物残渣吸附和包裹的金量占样品金总量的18%~22%,残渣中金的主要来源是已被王水溶解但被二氧化硅等胶状物包裹吸附而未进入溶液的金,其次是未被王水溶解的单质金。胶状物的形成与样品中钙镁硅含量有直接的关系,当CaCO3、MgCO3含量达到30%以上时,必须考虑残渣中的金,以保证金的测试结果准确。  相似文献   

20.
The microwave oven acid digestion technique has been routinely applied to the ICP-MS multielement analysis of whole powdered coal. Samples were treated with a mixture of HF/aqua regia/HClO4 in closed Teflon PFA vessels without any pre-treatment. Complete dissolution of the coal matrix is not required, but only one that results in quantitative and reproducible recovery of more than 40 trace elements with minimum digestion time, minimum use of reagents and minimal operator attendance. The precision of the analysis as well as the repeatability of the sample preparation procedure and precision of instrumental measurements have been evaluated. Eight coal standards, including NBS SRM 1632b, 3 South Africa Reference Materials (SARMs) 18 to 20 and 4 USA ARs 1800 to 1803 were analysed in this manner providing data for all the 14 rare earth elements along with others of geochemical interest, technological relevance as well as environmental and health concern. The results, from the ppb level to several ppm, are discussed for all the elements including detection and quantification limits, precision and accuracy. In general, good agreement was achieved with the certified and/or available published values.  相似文献   

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