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Cosmochemical and isotopic study of the origin and evolution of chondrites and achondrites, their genetic relationship and timescales.

球粒陨石和无球粒陨石的起源和演化、它们的遗传关系和时间尺度的宇宙化学和同位素研究。

基本信息

批准号：
14340171
负责人：
NAKAMURA Noboru
金额：
$ 8.45万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

In order to obtain new evidences constraining the timing, origin and evolution of primitive and differentiated meteorites and their genetic relationships, we have carried out chemical, petrological and isotopic analyses for chondrites and achondrites. Results are summarized bellow :(1)Under international consortium for the Kobe (CK) meteorite, we obtained a unique REE pattern and detailed chemical and petrological features, which constrains nebular fractionations and meteorite parent body processes of CK chondrites yielding silicate-darkening of the meteorites. The age determination by U-Pb and Rb-Sr methods were carried out for the meteorite, indicating complicated thermal histories of CK chondrite parent body.(2)REE and Rb-Sr isotopes were analyzed for the most pure matrix materials or chondrules from the Allende (CV) meteorite, respectively. REE results suggest that the precursor of matrix formed by nebular processes. The 4.4Ga alteration event was newly discovered from Rb-Sr system of Allende.(3)The precise Sm-Nd isotopic analyses were carried out for 5 acapulcoites : We obtained a significantly young age (4.13±0.10Ga) for one acapulcoite, indicating young thermal event on the parent body.(4)The low Pb blank technique for U-Pb dating was established and precise U-Pb ages as well as Sm-Nd and Rb-Sr ages and REE patterns were obtained for three newly found Antarctic Martian meteorites.(5)The Mo isotopic anomalies derived from stellar processes were discovered in primitive meteorites. Precise Cr and Ba isotopic analysis techniques were established and new isotopic anomalies were found for primitive and differentiated meteorites.(6)Precise chlorine isotopic analyses were carried out for Allende and 9 standard rocks using thermal ionization mass spectrometry (TIMS). We also established a high sensitivity negative TIMS for Cl.

为了获得制约原始陨石和分异陨石形成时间、成因演化及其成因关系的新证据，我们对陨石和无球粒陨石进行了化学、岩石学和同位素分析。（1）通过对科比（CK）陨石的研究，我们获得了独特的稀土元素配分模式和详细的化学岩石学特征，这些特征制约了CK陨石的星云分馏和陨石母体过程，导致了陨石的硅酸盐变暗。对该陨石进行了U-Pb和Rb-Sr年龄测定，表明CK球粒陨石母体具有复杂的热历史。（2）对阿连德（CV）陨石中最纯的基质物质或球粒分别进行了REE和Rb-Sr同位素分析。稀土元素分析结果表明，基质的前身物是由星云过程形成的。4.4Ga蚀变事件是在阿连德Rb-Sr体系中新发现的。（3）对5个榴辉岩进行了精确的Sm-Nd同位素分析，其中1个榴辉岩的年龄非常年轻（4.13±0.10Ga），表明其母岩发生了年轻的热事件。（4）建立了低铅空白U-Pb测年技术，获得了三块新发现的南极火星陨石的精确U-Pb年龄、Sm-Nd和Rb-Sr年龄以及REE模式。（5）在原始陨石中发现了来自恒星过程的Mo同位素异常。建立了精确的Cr和Ba同位素分析技术，并在原始陨石和分异陨石中发现了新的同位素异常。（6）采用热电离质谱（TIMS）技术对阿连德和9种标准岩石进行了氯同位素的精确分析。我们还建立了一个高灵敏度的负离子TIMS。