Isotopic and chronological studies of primitive Achondrites

为了研究早期太阳系火成岩过程中的精细时间尺度和详细的化学分馏，即从球粒陨石到非球粒陨石的分异，我们旨在建立精确的同位素分析方法，然后进行原始非球粒陨石的痕量同位素分析和准确的年龄测定，以及其他相关的陨石物质的分析。由于某公司MS9质谱仪的改装工作严重延误，在项目的第二年成功地对第一批标准样品和后来的原始非球粒陨石进行了同位素分析，这反过来又有望在不久的将来对陨石进行低空白水平的精确同位素工作，典型的是在不久的将来对原始非球粒陨石进行精确的年龄测定。本项目取得的成果如下：1.对质谱仪(MS9)的探测器(杯宽)进行了调整，使我们现在能够精确地分析痕量(最高可达几纳克)的Nd和Cr同位素，从而使我们认识到同位素测量中出现的新问题。已经建立了一个用于快速数据处理的新的计算机系统。对少数原始球粒陨石进行了额外的微量元素分析，并准备了原始球粒陨石的手稿，包括新的结果，供期刊投稿。对几个原始非球粒陨石的块状样品进行了精确的Sm-ND同位素分析。一颗火星陨石的精确年龄测定成功地进行了。

In order to investigate fine time-scales and detailed chemical fractionations during igneous processes in the early solar system, I.e. differtiation from chondrites to achondrites, we aimed in this work to establish analytical methods for precise isotopic analyses and then to carry out analyses of trace amounts of isotopes and accurate age determination for the primitive achondrites, as well as analyses of other related meteoritic materials. Due to heavy delay of modification works for the mass spectometer MS9 at a company, the isotopic analysis using the machine were carried out in the second year of the project for at first standard samples and later primitive achondrites successfully, which is in turn promising future low-blank level, precise isotopic works for meteorites, typically for precise age determination of primitive achondrites in the near future. Results obtained in this project are as follows ;1. Adjustment of detectors (cup widths) of the mass spectormeter (MS9) were performed, which enable us now to analyze precisely trace amounts (up to a few nanogram of Nd) of Nd and Cr isotopes and then led us to recognition of new problems arise in isotopic measurements.2. A new computer system for the fast data processes has been established3. Additional trace element analyses were carried out for a few primitive achodrites, and then a manuscript of primitive chondrites including new results has been prepared for journal submission.4. Precise Sm-Nd isotopic analyses were carried out for bulk samples of a few primitive achondrites.5. The precise age determination of a martian meteorite was carried out successfully.