月球岩浆海洋的氯同位素指纹图谱。
The chlorine isotope fingerprint of the lunar magma ocean.
作者信息
Boyce Jeremy W, Treiman Allan H, Guan Yunbin, Ma Chi, Eiler John M, Gross Juliane, Greenwood James P, Stolper Edward M
机构信息
Division of Geological and Planetary Sciences, Caltech, 1200 East California Boulevard, Pasadena, CA 91125, USA. ; Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA.
Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA.
出版信息
Sci Adv. 2015 Sep 25;1(8):e1500380. doi: 10.1126/sciadv.1500380. eCollection 2015 Sep.
The Moon contains chlorine that is isotopically unlike that of any other body yet studied in the Solar System, an observation that has been interpreted to support traditional models of the formation of a nominally hydrogen-free ("dry") Moon. We have analyzed abundances and isotopic compositions of Cl and H in lunar mare basalts, and find little evidence that anhydrous lava outgassing was important in generating chlorine isotope anomalies, because (37)Cl/(35)Cl ratios are not related to Cl abundance, H abundance, or D/H ratios in a manner consistent with the lava-outgassing hypothesis. Instead, (37)Cl/(35)Cl correlates positively with Cl abundance in apatite, as well as with whole-rock Th abundances and La/Lu ratios, suggesting that the high (37)Cl/(35)Cl in lunar basalts is inherited from urKREEP, the last dregs of the lunar magma ocean. These new data suggest that the high chlorine isotope ratios of lunar basalts result not from the degassing of their lavas but from degassing of the lunar magma ocean early in the Moon's history. Chlorine isotope variability is therefore an indicator of planetary magma ocean degassing, an important stage in the formation of terrestrial planets.
月球含有氯，其同位素与太阳系中迄今研究过的任何其他天体都不同，这一观测结果被解释为支持传统的月球形成模型，即名义上无氢（“干燥”）的月球。我们分析了月海玄武岩中氯和氢的丰度及同位素组成，几乎没有发现证据表明无水熔岩排气在产生氯同位素异常方面很重要，因为（37）Cl/（35）Cl比值与氯丰度、氢丰度或D/H比值之间的关系与熔岩排气假说不一致。相反，（37）Cl/（35）Cl与磷灰石中的氯丰度以及全岩钍丰度和镧/镥比值呈正相关，这表明月球玄武岩中高的（37）Cl/（35）Cl是继承自原始钾稀土元素富集物（urKREEP），即月球岩浆海洋的最后残余物。这些新数据表明，月球玄武岩中高的氯同位素比值并非源于其熔岩的排气，而是源于月球历史早期月球岩浆海洋的排气。因此，氯同位素变化是行星岩浆海洋排气的一个指标，这是类地行星形成过程中的一个重要阶段。
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