Heavy noble gas signatures of the North Atlantic Popping Rock 2ΠD43: Implications for mantle noble gas heterogeneity
Heavy noble gas signatures of the North Atlantic Popping Rock 2ΠD43: Implications for mantle noble gas heterogeneity
复制标题
北大西洋 Popping Rock 2ΠD43 的重惰性气体特征：对地幔惰性气体非均质性的影响
DOI：
10.1016/j.gca.2020.11.011
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发表时间：
2020
影响因子：
5
通讯作者：
S. Mukhopadhyay
中科院分区：
文献类型：
--
作者：
R. Parai;S. Mukhopadhyay
重惰性气体(Ne、Ar、Xe)同位素组成对地幔非均质性的性质具有很强的制约作用。北大西洋爆裂岩样2ΠD43异常富含天然气，长期以来一直是我们理解大洋中脊玄武岩地幔源区惰性气体组成的基础。本文介绍了新的高精度He、Ne、Ar和Xe同位素组成以及在2ΠD43样品裂解中测得的He、Ne、Ar和Xe丰度。在校正了同步至喷发后大气污染的测量值后，我们估算出2 D43的地幔源区21Ne/22Ne为0.0590 ±0.0002，40Ar/36Ar为23,900 ± 100,129Xe/130Xe为7.41 ± 0.02。大气Xe向北大西洋爆裂岩石地幔来源的显著聚集是明显的，尽管差异聚集不能解释MORB和来自羽流的特征之间的系统变化。相反，2ΠD43地幔源区的裂隙成因Xe同位素特征表明，上地幔相对于地幔有更大程度的长期脱气作用，从而解释了稀有气体的强烈同位素变化。爆裂岩石数据还进一步证明，在地球历史的第一个100Myr期间，MORB地幔与为烟柱源提供惰性气体的储气库不同，这两个储气库并没有通过4.45 Ga的地幔对流而被均化。
Heavy noble gas (Ne, Ar, Xe) isotopic compositions provide powerful constraints on the nature of mantle heterogeneities. The North Atlantic popping rock sample 2ΠD43 is unusually gas-rich and has long formed the basis of our understanding of the noble gas composition of the mid-ocean ridge basalt (MORB) mantle source. Here we present new high-precision He, Ne, Ar and Xe isotopic compositions as well as He, Ne, Ar and Xe abundances measured in a split of the 2ΠD43 sample. After correcting the measured values for syn- to post-eruptive atmospheric contamination, we estimate a mantle source21Ne/22Ne of 0.0590 ± 0.0002,40Ar/36Ar of 23,900 ± 100 and129Xe/130Xe of 7.41 ± 0.02 for 2ΠD43. Significant regassing of atmospheric Xe into the North Atlantic popping rock mantle source is evident, though differential regassing cannot explain systematic variations between MORB and plume-derived signatures. Rather, the fissiogenic Xe isotope signature of the 2ΠD43 mantle source indicates a greater extent of long-term degassing of the upper mantle relative to the plume mantle to explain heavy noble gas isotopic variations. The popping rock data also add to growing evidence that the MORB mantle differentiated from the reservoir supplying noble gases to plume sources within the first 100 Myr of Earth history, and that the two reservoirs have not been homogenized though 4.45 Ga of mantle convection.