Investigation on recycling and evolution of crust and mantle materials based on noble gas isotope ratios and Ar-Ar dating

基于稀有气体同位素比值和Ar-Ar测年的壳幔物质循环与演化研究

基本信息

批准号：
12440145
负责人：
KANEOKA Ichiro
金额：
$ 9.6万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

We have performed the investigation on the recycling and evolution of crust and mantle materials based on noble gas isotope ratios and Ar-Ar dating in order to clarify the system and obtained the following results.We found 3He/4He ratios of less than the atmospheric value in some mantle xenoliths from Sikhote Alin area, east Siberia. Based on the micro-Raman spectroscopic analysis of CO2 inclusions in olivine and pyroxene crystals, we have developed a method to evaluate the trapping pressure of CO2. By using the method, wee could estimate the trapping pressure for Sikhote Alin samples, which indicated the pressure of 0.96〜1.04Gpa, corresponding to the depth of about 30km. From such information, it is inferred that old subducted crustal materials might have affected the 3He/4He ratios and probably also affected the trace element compositions underneath the east Siberian continent. Furthermore, Ar-Ar dating for phlogopite in Horoman Peridotite Complex indicates an Ar-Ar age of about 21Ma with a signature of the occurrence of excess 40Ar. It suggests that the phlogopite might have formed secondarily at a depth where the atmospheric component affected to some extent through water. On the other hand, noble gas analysis for glassy samples which were collected by submersibles from the Loihi Volcano area suggests the effect of oceanic crustal materials. Noble gas analysis for samples from Reunion and Mauritius Islands indicate the lowering of 3He/4He ratios for samples of less than 1Ma from Mauritius Island compared to those of older samples from the island and those of Reunion Island. This seems to indicate the evolutional trend of a hotspot type oceanic island.

我们已经对基于高贵的气体同位素比和AR-AR约会的地壳和地幔材料的回收和演变进行了研究，以澄清系统并获得以下结果。我们发现，在Sikhote Alin Alin Alin Alin Alin，East Siberia的某些地幔Xenoliths中发现了3HE/4HE的比率小于大气值。基于橄榄石和辉石晶体中二氧化碳夹杂物的微拉曼光谱分析，我们开发了一种评估二氧化碳压力的方法。通过使用该方法，我们可以估计锡科特Alin样品的捕获压力，这表明压力为0.96至1.04GPA，对应于约30公里的深度。从这些信息中可以推断出，旧的俯冲地壳材料可能影响了3HE/4HE的比率，并且可能还影响了东西伯利亚大陆下方的微量元素组成。此外，在Horoman橄榄石配合物中的磷灰石的Ar-Ar日期表明，AR-AR年龄约为21mA，具有多余40AR的签名。它表明，磷酸磷酸盐可能在深度形成了次级，在某种程度上，大气成分在某种程度上通过水影响。另一方面，对玻璃状样品的贵重气体分析是由洛伊希火山区域的潜水物收集的，这表明海洋壳材料的影响。与毛里求斯岛的样本相比，来自毛里求斯岛的样本的贵重气体分析表明，与该岛和团圆岛的老年样品相比，毛里求斯岛少于1MA的样品的3HE/4HE比降低。这似乎表明了热点型海洋岛的进化趋势。