Mineral chemistry and in situ U–Pb geochronology of the mare basalt Northwest Africa 10597: Implications for low-Ti mare volcanism around 3.0 Ga
Mineral chemistry and in situ U–Pb geochronology of the mare basalt Northwest Africa 10597: Implications for low-Ti mare volcanism around 3.0 Ga
复制标题
西北非洲 10597 月海玄武岩的矿物化学和原位 U-Pb 年代学：对 3.0 Ga 左右低 Ti 月海火山活动的影响
DOI：
10.1016/j.icarus.2019.113531
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发表时间：
2020
期刊：
影响因子：
3.2
通讯作者：
Weibiao HSU
中科院分区：
文献类型：
--
作者：
Yunhua WU;Weibiao HSU
Unbrecciated mare basalts are rare in the lunar meteorite collection. Found in 2015, Northwest Africa (NWA) 10597 is a medium-grained low-Ti mare basalt with a subophitic texture. The meteorite consists mostly of mm-sized pyroxene and plagioclase, with minor olivine, spinel, ilmenite, phosphates, silica, and trace Zr-rich minerals, such as baddeleyite, zirconolite and tranquillityite. A portion of plagioclase and silica has been transformed to their high-pressure polymorphs due to shock metamorphism. NWA 10597 has a low TiO2content (2.9 wt%) but is relatively enriched in rare earth elements (REE) (Laaverage= 65 × CI) with an overall unfractionated pattern except for a negative Eu anomaly. Calculated REE concentrations of parent melts in equilibrium with Mg-rich pyroxene and Ca-rich plagioclase suggest no significant assimilation of REE-rich melts after the onset of pyroxene crystallization. In situ Usingle bondPb analyses of baddeleyite and apatite reveal a mutually consistent age of ~3.0 Ga, which is also in excellent agreement with that of low-Ti mare basalts NWA 4734 and LaPaz Icefield (LAP) 02205 dated with other independent techniques. The concordance suggests no significant thermal disturbance in the Usingle bondPb isotopic system of NWA 10597 although it was heavily shocked. NWA 10597 closely resembles NWA 4734 in terms of petrographic texture, mineral chemistry and geochronology, indicating a pairing relationship.
