study on the environmental and material evolution in the early system solar based on the chemical of composition of meteorites

今年是该项目的最后一年。在这一年里，我们进行了以下研究课题：（i）固体硅酸盐材料中四种卤素分析技术的建立及其在陨石样品中的应用;（ii）陨石中难熔亲铁元素的分布及其宇宙化学意义;（iii）陨石中稀土元素、Th和U的分布及其宇宙化学意义;及（iv）发展适用于陨石样本的分析技术。在第一个课题中，我们建立了一个在50 - 100毫克重的单一样品中测定四种卤素的分析方法，并将其应用于南极陨石样品。研究了Cl、Br和I在陨石中的分布，发现I在辉石和斜长石中有不同程度的分布，与Cl、Br不同。这一观察结果对于研究I的宇宙化学行为似乎非常重要，而I的宇宙化学行为还没有得到很好的描述。对于第二个主题，我们确定了火星陨石中的难熔亲铁元素，并观察到火星陨石中含有10^<-2>到10^<-3>x Cl的这些元素。这可以理解为在芯形成后添加亲铁元素作为最后的饰面。第三个课题刚刚完成，与此课题相关的论文即将准备。本课题测定了球粒中的稀土元素、钍元素和铀元素，观察到它们的丰度随母体热变质作用的活动而变化。

This year is the last year of the project. In this year, we have conducted the following research subjects ; (i) establishment of the analytical technique for four halogens in solid silicate materials and its application to meteorite samples, (ii) distribution of refractory siderophile elements in meteorites and its cosmochemical implications, (iii) distribution of rare earth elements (REEs), Th and U in meteorites and its cosmochemical implications, and (iv) development of analytical techniques applicable to meteorite samples. For the first subject, we established an analytical method for determining four halogens in a single sample weighing 50 to 100 mg and applied it to chondritic meteorite samples. We also investigated the distribution of Cl, Br and I in chondritic meteorites and observed that I is distributed in pyroxene and/or plagioclase to some extent, being different from Cl and Br. This observation seems to be very important in considering cosmochemical behavior of I, which has not been well described yet. For the second subject, we determined refractory siderophile elements in martian meteorites and observed that martian meteorites contain these elements at a level of 10^<-2> to 10^<-3> x Cl. This is understood in terms of an addition of siderophile elements as a last veneer after the formation of core. The third subject has just completed and the paper related with this subject will be prepared soon. In this subject, we determined REEs, Th and U in chondrules and observed that their abundances change in accordance with the activity of thermal metamorphism in the parent body.