Mineralogical, REE and 146Sm-142Nd isotopic systematics of the earliest solar condensates in unequilibrated Enstatite chondrites

不平衡顽火辉石球粒陨石中最早太阳凝聚物的矿物学、稀土元素和 146Sm-142Nd 同位素系统学

• 批准号: 211141497
• 负责人: Professor Dr. Ahmed El Goresy (†)
• 金额: --
• 依托单位: Bayerisches Forschungsinstitut für Experimentelle Geochemie und Geophysik (BGI)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/211141497?language=en
• 关键词: Mineralogical; REE; 146Sm; 142Nd; isotopic

Enstatite chondrites store chemical and isotopic signatures reflecting formational conditions at low oxygen fugacity. There is however no agreement on their birth place, history and locality of formation: (1) While the majority of scholars agree on their formation in the earliest episodes of the solar nebula, (2) Several scholars in the USA advocate for their evolution by impact melting in pre-existing asteroids. It is also disputed if the two subgroups: EH (high iron) and EL (low iron) emerged from the same parental asteroids. A further uncertainty is if individual EH, on the one hand and individual EL chondrites on the other came from different asteroids or from the same parent body. Bulk mineralogy and mineral chemistry in EH and EL chondrites are different and allow a clearcut recognition of EH from EL. The condensation scheme considers oldhamite (CaS) to be one of the earliest condensates at C/O ratios from > 0.83 < 0.95. CaS incorporated the majority of the REE and Actinides during condensation as sulfides. In contrast, the impact melting model considers CaS to have formed by impact melting. A mineralogical study of oldhamite and associated minerals, their REE patterns, their 146Sm/142Nd isotopic system (T1/2 = 103 Myr) and Pb-Pb ages of oldhamite and other sulfide generations in individual EH- and EL-chondrites is being conducted. Aims of this multitask scrutiny are to uncover: (1) REE signatures and 146Sm/142Nd isotopic systematics of oldhamites in EH-3 and in EL-3 chondrites, and if they are different (2) chronological details of condensation and/or accretionary and parent body events in earliest episode of the solar nebula, (3) C-, N- and H-isotopic investigations of different graphite types in EL-3 and of N in sinoite (Si2N2O) in the EL-3 in Almahata Sitta CT3 asteroid. Mineralogical, petrological and isotopic investigations of the newly recovered differentiated meteorite NWA7325 that was presumably ejected from the planet Mercury.

Enstatite软管存储化学和同位素特征，反映了低氧赋形性的形成条件。但是，他们的出生地点，历史和地形地区尚无协议：（1）大多数学者在太阳星云的最早事件中同意他们的形成，（2）美国在美国的几名学者倡导其进化，以影响预先存在的小行星。如果两个亚组：EH（高铁）和EL（低铁）也是从同一父母的小星形出现的，这也是有争议的。进一步的不确定性是，一方面，另一方面是单个EH，另一方面是单个El软骨，另一只来自不同的小行星或同一母体。 EH和EL软骨的散装矿物学和矿物化学是不同的，并且可以清楚地识别EL的EH。冷凝方案认为Oldhamite（CAS）是最早的C/O比率之一，> 0.83 <0.95。 CAS作为硫化物在凝结过程中纳入了大多数REE和肌动剂。相反，影响熔化模型认为CAS是由冲击熔化形成的。对Oldhamite和相关矿物质的矿物学研究，其REE模式，其146SM/142ND同位素系统（T1/2 = 103 Myr）以及Oldhamite的PB-PB年龄以及其他EH-和El-El-Condrites中其他硫化物的年龄。这项多项审查的目的是要揭示：（1）REE签名和146SM/142nd的EH-HAMITE和EL-3中的Oldhamites的同位素系统学和EL-3软管中，以及如果它们是不同的（2）缩聚和/或缩水和/或最早的缩水和父母事件的时间，则是Solar Nebula nebula nebula neb和nebula nebula ne neb和solar nebula ne neb-n neb-nebula ne-n neb-neb-neb-neb-neb-neb-neb-neb。 EL-3中的石墨类型和n中的N中的N中的n（Si2n2O）中的EL-3中的n almahata sitta ct3小行星中的石墨类型。对新恢复的分化陨石NWA7325的矿物学，岩石学和同位素研究，大概是从汞行星弹出的。