Combined investigation of H isotopic compositions and U-Pb chronology of young Martian meteorite Larkman Nunatak 06319
Combined investigation of H isotopic compositions and U-Pb chronology of young Martian meteorite Larkman Nunatak 06319
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DOI：
10.2343/geochemj.2.0424
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发表时间：
2016-09
影响因子：
0.8
通讯作者：
M. Koike;Y. Sano;N. Takahata;A. Ishida;N. Sugiura;M. Anand
中科院分区：
文献类型：
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作者：
M. Koike;Y. Sano;N. Takahata;A. Ishida;N. Sugiura;M. Anand
我们测量了一个年轻的火星陨石LAR 06319中磷酸盐矿物的氢同位素组成（D/H比）和U-Pb年代学。陨石中熔融包裹体的D/H比也被研究，以评估火星上最近是否存在水库。多颗粒磷灰石和钠长石的总Pb/U测年结果一致，为167 ± 57 Ma，解释为结晶年龄，表明该陨石中的磷灰石和钠长石都保留了它们的岩浆历史。磷灰石颗粒的D/H比值具有很好的重复性，δD值为4250 ± 120 ‰，而钠长石颗粒的D/H比值变化较大，最大δD值为5260 ± 790 ‰。熔体包裹体中的镁铁玻璃的δD值变化很大，约为0.001 ~ 0.005。1070 ‰ ~ 6830 ± 460 ‰。在这些阶段记录的不同的D/H签名反映了不同的含水组分的贡献，不同的D/H比，可能在不同的时间合并。据推测，几个同位素不同的水库存在于目前的火星表面/次表面系统。
We measured the hydrogen isotopic composition (D/H ratios) and U-Pb chronology of phosphate minerals in a young Martian meteorite: LAR 06319. D/H ratios of melt-inclusions in the meteorite were also investigated to evaluate the presence of water reservoirs on Mars in recent times. The total Pb/U dating of multiple grains of apatite and merrillite yield a concordant date of 167 ± 57 Ma, interpreted as the crystallization age, suggesting that both apatite and merrillite in this meteorite have preserved their igneous histories. The D/H ratios of an apatite grain show good reproducibility yielding a δD value of 4250 ± 120 ‰, whereas those of merrillite show larger D/H variations with the maximum δD value of 5260 ± 790 ‰. However, mafic glass in melt-inclusions shows extremely large variation in δD, ranging from ca. 1070 ‰ to 6830 ± 460 ‰. The different D/H signatures recorded in these phases reflect the contributions of different hydrous components with distinct D/H ratios, possibly incorporated at different times. It is inferred that several isotopically distinct water reservoirs exist in the present Martian surface/sub-surface system.