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Evaluation of Solar System Abundaces of the Elements based on Analytical Data of Meteorites

基于陨石分析数据评价太阳系元素丰度

基本信息

批准号：
05453012
负责人：
EBIHARA Mitsuru
金额：
$ 4.42万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

The concentrations of ReOs and Ir in Antarctic unequilibrated ordinary chondrites (UOC) were determined by radiochemical neutron activation analysis. Large fractionations among these elements were found in Antarctic UOC.Average Re/Os and Re/Ir rations in ordinary chondrites are 25-30% higher than those in C1 chondrites and 10-15% higher than those in C2 and C3 chondrites. In contrast, the Os/Ir ratio is not variable among these chondrite groups. It is therefore suggested that Re is fractionated among ordinary and carbonaceous chondrites. Atom abundances of Os and Ir relative to 10^6 Si atoms of H chondrites are nearly equal to those of C1 chondrites, but their Re value is 30% higher than the C1 value. Considering that the currently accepted value for solar system abundance of Re (0.517 atom relative to 10^6 Si atoms, Anders and Grevesse, 1989) is the lowest value among (Si-normalized) Re abundances in C1, C2, C3 and H chondrites, its value should be changed to a larger value. If C2 cho … More ndrites are adopted as the solar system standard, the solar system abundance of Re is changed to 0.0589, with those of Os and Ir being 0.740 and 0.685, respecitively, at the same time.Inductively coupled plasma mass spectormetry (ICP-MS) was successfully applied to the bulk sample of Allende, Jilin, Modoc, Saint-Severin and Atlanta for the determination of rare earth elements (REE) (Y and 14 lanthanoids), Th and U.The results of ICP-MS showed a good agreement with recommended values and their reproducibilities were high enough to discuss the detailed abundances of lanthanoids and actinoids in chondritic meteorites. For the Allende reference sample issued by the Smithsonian Institution, a positive anomaly of Tm, a fractionation between light REE and heavy REE and a high Th/U ratio were observed in the CI-normalized abundances of REE,Th and U.These features are common for group II inclusions in Allende, suggesting that the abundances of refractory lithophiles in Allende are somewhat influenced by those in a specific constituent. For the other chondritic meteorites, the zigzag change was commonly observed in the heavy REE region of their CI-normalized abundance patterns. It is suggested that such a zigzag pattern is attributable to erratically high abundances of mono-isotopic REE (Tb, Ho and Tm) for CI values. Less

用放化中子活化法测定了南极非平衡普通球粒陨石(UOC)中REO和Ir的含量。普通球粒陨石的Re/Os和Re/Ir比值比C_1球粒陨石高25~30%，比C_2和C_3球粒陨石高10~15%。相反，Os/Ir比值在这些球粒陨石群中没有变化。因此，认为Re在普通球粒陨石和碳质球粒陨石中是分馏的。相对于H球粒陨石中10^6的Si原子，Os和Ir的原子丰度几乎与C_1球粒陨石相同，但它们的Re值比C_1值高30%。考虑到目前被接受的太阳系Re丰度值(0.517个原子相对于10^6个Si原子，Anders和Grevesse，1989年)是C1、C2、C3和H球粒陨石中(Si归一化的)Re丰度中最低的值，它的值应该改变为更大的值。如果C2 CHO…采用更多的Ndite作为太阳系标准，Re的太阳系丰度改变为0.0589，Os和Ir的丰度分别为0.740和0.685。电感耦合等离子体质谱(ICPMS)成功地应用于阿连德、吉林、莫多克、圣塞韦林和亚特兰大的稀土元素(Y和14种稀土元素)、Th和U的测定，结果与推荐值一致，重现性较高，足以详细讨论球粒陨石中稀土元素和阳离子的丰度。对于Smithsonian研究所发布的Allende标准样品，在CI归一化的REE、Th和U的标准化丰度中，观察到Tm的正异常、轻稀土和重REE的分馏以及高的Th/U比值，这些特征是Allende中II类包裹体的共同特征，表明Allende中难熔亲石体的丰度受到特定组分的影响。对于其他球粒陨石，在其CI归一化丰度模式的重稀土区域通常观察到之字形变化。结果表明，这种“之”字形模式是由于单一同位素稀土元素(Tb、Ho和Tm)的CI值异常高所致。较少