Evaporation Experiments on Planetary Materials.

行星材料的蒸发实验。

基本信息

批准号：
05833009
负责人：
TSUCHIYAMA Akira
金额：
$ 1.34万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Evaporation rates and their evaporation coefficients of important minerals forming terrestrial planets (forsterite, metallic iron, and troilite) were determined by evaporation experiments. Forsterite evaporates congruently, and the evaporation obeys a linear rate law. Its evaporation coefficient showed that the evaporation of forsterite under a H_2-rich atmosphere occurs by mechanism similar to that of free evaporation. From the results, evaporation rates of forsterite in a primordial solar nebula can be estimated. Evaporation of metallic iron also obeys a linear rate law, and its evaporation coefficient is close to unity. Incongruent evaporation of troilite with metallic iron residue obeys a linear rate law due to reaction at the troilite-metallic iron interface as a rate-determining process. From the experimental results together with previous data, evaporation rates of important minerals forming terrestrial planets were complied. Elemental fractionation (Mg/Si and Fe/S) due to evaporation of mineral dust in the primordial solar nebula was discussed based on the complied data. It was suggested that incongruent evaporation of enstatite did not occur but apparent congruent evaporation of enstatite occurred, and thus no Mg/Si fractionation is expected. However, Mg/Si fractionation is possible as long as the dust was amorphous Mg-silicate. Fe/S fractionation was expected due to incongruent evaporation of troilite. A model for isotopic mass fractionation due to evaporation of solids was also constructed based on the evaporation rates of the minerals. The fractionation depends on the evaporation rate, diffusion coefficient in the solid, the size of the solid, and isotopic fractionation factor which is determined from the mass of evaporated molecules. Based on the model, conditions for isotopic mass fractionation found in meteorites were estimated successfully.

蒸发率及其蒸发系数通过蒸发实验确定了形成陆地行星（脱石油，金属铁和曲折）的重要矿物的蒸发率。脚石会一致地蒸发，蒸发服从线性速率定律。它的蒸发系数表明，在富含H_2的气氛下，通过与游离蒸发相似的机制发生了稀释液的蒸发。从结果来看，可以估计原始太阳星云中的稀释石的蒸发速率。金属铁的蒸发也遵守线性速率定律，其蒸发系数接近统一。金属铁残基对Troilite的不一致蒸发遵守线性速率定律，这是由于Troilite金属铁界面的反应，作为速率确定的过程。从实验结果以及以前的数据中，遵守了重要的矿物质矿物质的蒸发率。根据符合数据，讨论了原始太阳星云中矿物灰尘蒸发引起的元素分馏（mg/si和fe/s）。有人提出，没有发生不一致的eNSTATITE蒸发，但明显的enstatite蒸发发生了，因此预计不会进行MG/SI分馏。但是，只要灰尘是无定形的mg-silicate，MG/Si分级就可以。由于Troilite的不一致蒸发，预计Fe/S分馏。还基于矿物质的蒸发速率构建了由于固体蒸发而导致的同位素质量分馏的模型。分馏取决于蒸发速率，固体的扩散系数，固体的大小和同位素分级因子，该因子是由蒸发分子质量确定的。基于该模型，成功估算了在陨石中发现的同位素质量分馏的条件。