Evidence for extremely rapid magma ocean crystallization and crust formation on Mars.
Evidence for extremely rapid magma ocean crystallization and crust formation on Mars.
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DOI：
10.1038/s41586-018-0222-z
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发表时间：
2018-06
期刊：
影响因子：
64.8
通讯作者：
Bizzarro M
中科院分区：
文献类型：
--
作者：
Bouvier LC;Costa MM;Connelly JN;Jensen NK;Wielandt D;Storey M;Nemchin AA;Whitehouse MJ;Snape JF;Bellucci JJ;Moynier F;Agranier A;Gueguen B;Schönbächler M;Bizzarro M
原始地壳的形成是类地行星演化的关键一步，但人们对这一过程的时间知之甚少。矿物锆石是制约地壳形成的有力工具，因为它可以用U-Pb系统准确地测定年龄，并且不受后续蚀变的影响。此外，由于锆石中的Hf含量较高，可以利用176Lu-176Hf衰变系统来确定其源岩储集层的性质和形成时间尺度。在火星陨石中发现了古老的火成岩锆石，年龄约为4430 Ma，据信是来自火星南部高地的风化角砾岩。这些锆石存在于演化的岩性中，被解释为反映重新熔化的原始火星地壳，从而潜在地为火星早期地壳演化提供了独特的见解。本文报道了NWA7034火星风化角砾岩中古锆石的高精度U-Pb年龄和Hf同位素组成。7个锆石的U-Pb年龄基本一致，207Pb/206Pb的年龄范围从4476.3±0.9 Ma到4429.7±1.0 Ma，其中包括来自火星的最古老的直接测年物质。所有的锆石都记录了从不晚于4547 Ma的原始地幔中提取的富集型安山岩地壳中继承的非放射性成因的初始Hf同位素组成。因此，当时火星上存在着一个原始地壳，并存活了大约100英里，然后被重新加工，可能是受到撞击，产生了岩浆，锆石从中结晶出来。考虑到稳定的原始地壳的形成是行星分化的最终产物，我们的数据要求火星上的吸积、核心形成和岩浆海洋结晶在太阳系形成后20英里内完成。这些时间尺度支持的模型表明，岩浆海洋快速结晶导致重力不稳定的层状地幔，随后倾覆导致上升的堆积物减压熔融，并从原始玄武岩到安山岩地壳的提取。
The formation of a primordial crust is a critical step in the evolution of terrestrial planets but the timing of this process is poorly understood. The mineral zircon is a powerful tool for constraining crust formation as it can be accurately dated with the U-Pb system and is resistant to subsequent alteration. Moreover, the high concentration of Hf in zircon allow for the utilization of the 176Lu-176Hf decay system to determine the nature and formation timescale of its source reservoir. Ancient igneous zircons with ages of ~4430 Ma have been reported in martian meteorites believed to represent regolith breccias from the southern highlands of Mars. These zircons are present in evolved lithologies interpreted to reflect re-melted primary martian crust thereby potentially providing unique insights into early crustal evolution on Mars. Here, we report concomitant high-precision U-Pb ages and Hf-isotope compositions of ancient zircons from the NWA 7034 martian regolith breccia. Seven zircons with mostly concordant U-Pb ages define 207Pb/206Pb dates ranging from 4476.3±0.9 Ma to 4429.7±1.0 Ma, including the oldest directly dated material from Mars. All zircons record unradiogenic initial Hf-isotope compositions inherited from an enriched, andesitic-like crust extracted from a primitive mantle no later than 4547 Ma. Thus, a primordial crust existed on Mars by this time and survived for ~100 Myr before it was reworked, possibly by impacts, to produce magmas from which the zircons crystallized. Given that formation of a stable primordial crust is the end product of planetary differentiation, our data require that the accretion, core formation and magma ocean crystallization on Mars was completed <20 Myr after Solar System formation. These timescales support models suggesting rapid magma ocean crystallization leading to a gravitationally unstable stratified mantle, which subsequently overturns resulting in decompression melting of rising cumulates and extraction of a primordial basaltic to andesitic crust.
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影响因子：
3.9
作者：
Gerstenberger, H;Haase, G
通讯作者：
Haase, G
影响因子：
5.3
作者：
Bellucci, J. J.;Nemchin, A. A.;Zanda, B.
通讯作者：
Zanda, B.
影响因子：
3.9
作者：
Connelly, J. N.;Ulfbeck, D. G.;Housh, T.
通讯作者：
Housh, T.
影响因子：
3.9
作者：
Mattinson, JM
通讯作者：
Mattinson, JM
DOI：
10.1111/j.1751-908x.2003.tb00641.x
发表时间：
2003-01-01
期刊：
GEOSTANDARDS NEWSLETTER-THE JOURNAL OF GEOSTANDARDS AND GEOANALYSIS
影响因子：
--
作者：
Bizzarro, M;Baker, JA;Ulfbeck, D
通讯作者：
Ulfbeck, D