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

为了获得约束原始陨石和分异陨石的形成时间、起源、演化及其成因关系的新证据，我们对球粒陨石和非球粒陨石进行了化学、岩石学和同位素分析。研究结果如下：(1)在神户陨石国际联合体的指导下，我们获得了独特的稀土配分模式和详细的化学和岩石学特征，制约了神户陨石球粒陨石的星云分馏和陨石母体过程，使陨石的硅酸盐变暗。对陨石进行了U-Pb法和Rb-sr法测年，显示了CK球粒陨石母体复杂的热历史。(2)对Allende(CV)陨石中最纯的基质物质或球粒陨石进行了REE和Rb-Sr同位素分析。REE结果表明，基质的前体是由星云过程形成的。(3)对5块无铅陨石进行了高精度的Sm-Nd同位素分析，其中1块无铅陨石获得了相当年轻的年龄(4.13±0.10Ga)，表明母体发生了年轻的热事件。(4)建立了低铅空白U-Pb定年技术，获得了3块新发现的南极火星陨石的精确U-Pb年龄、Sm-ND、Rb-Sr年龄和稀土元素配分模式。建立了精密的铬、巴同位素分析技术，发现了原始陨石和分异陨石的新的同位素异常。(6)用热电离质谱(TIMS)对阿连德和9种标准岩石进行了精确的氯同位素分析。我们还建立了对氯的高灵敏度负TIMs。

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.