A global rain of micrometeorites following breakup of the L‐chondrite parent body—Evidence from solar wind‐implanted Ne in fossil extraterrestrial chromite grains from China
A global rain of micrometeorites following breakup of the L‐chondrite parent body—Evidence from solar wind‐implanted Ne in fossil extraterrestrial chromite grains from China
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L-球粒陨石母体破碎后的全球微陨石雨——来自中国地外铬铁矿化石颗粒中太阳风注入氖的证据
DOI：
10.1111/j.1945-5100.2012.01394.x
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发表时间：
2012
影响因子：
2.2
通讯作者：
R. Wieler
中科院分区：
文献类型：
--
作者：
C. Alwmark;B. Schmitz;M. Meier;H. Baur;R. Wieler
摘要：先前对瑞典和中国的中奥陶纪石灰岩床的研究表明，在小行星带中的L球粒陨石母体破裂后，地球上大约470 Ma的地外物质流入量至少增加了两个数量级。 被发现的地外物质包括化石陨石和沉积物分散的地外铬铁矿（SEC）颗粒，两者都具有L-Arrhetic起源。对瑞典一个石灰岩部分的SEC颗粒进行的Ne同位素分析显示，绝大多数颗粒是作为微陨石运送到地球的。本研究在时间和地理上扩展了前人的工作，测量了来自中国当代中奥陶世灰岩剖面的三个不同层位的单个SEC颗粒（直径60-120 μm）中Ne的浓度和同位素比值。 所有中国的SEC颗粒，总共44个，都含有表面注入的分馏太阳风成分的Ne，这意味着这些颗粒，就像瑞典的SEC颗粒一样，作为微陨石被运送到地球。这提供了进一步令人信服的证据，表明L球粒陨石母体解体后微陨石物质流入量增加了两到三个数量级，这确实是一个全球性事件。微陨石雨盛行至少2 Myr（最高层的中国床沉积的估计时间）后，分裂事件。
Abstract– Previous studies of limestone beds of mid‐Ordovician age from both Sweden and China show that the Earth saw an at least two orders of magnitude increase in the influx of extraterrestrial material approximately 470 Ma, following the disruption of an L‐chondrite parent body in the asteroid belt. Recovered extraterrestrial material consists of fossil meteorites and sediment‐dispersed extraterrestrial chromite (SEC) grains, both with L‐chondritic origin. Ne isotope analysis of SEC grains from one of the Swedish limestone sections revealed that the vast majority of the grains were delivered to Earth as micrometeorites. In this study, we extend the previous work, both in time and geographically, by measuring concentrations and isotopic ratios of Ne in individual SEC grains (60–120 μm in diameter) from three different beds from a contemporary Middle Ordovician limestone section in China. All of the Chinese SEC grains, 44 in total, contain surface‐implanted Ne of fractionated solar wind composition, implying that these grains were, as in the case of the Swedish SEC grains, delivered to Earth as micrometeorites. This gives further compelling evidence that the two to three orders of magnitude increase in the influx of micrometeoritic material following the breakup of the L‐chondrite parent body was indeed a global event. The rain of micrometeorites prevailed for at least 2 Myr (the estimated time of the deposition of the topmost Chinese bed) after the breakup event.