Terrestrially occurring iron silicide spherules, described in the geological literature for 160 years as cosmogenic and approved as “extraterrestrial” minerals by IMA CNMMN in 1984, so far have escaped any serious examination by meteoriticists. Our isotopic and REE data, obtained for silicide spherules for the first time, disagree with the meteoritic origin of gupeiite (Fe₃Si) and xifengite (Fe₅Si₃) spherules from two continents. Despite departures from terrestrial norms (⁸⁷Rb/⁸⁶Sr—0.0174; ⁸⁷Sr/⁸⁶Sr—0.700181; ³He/⁴He—7.57 × 10⁻⁶; ⁴⁰Ar/³⁶Ar—325.9), the compositions of ¹⁴³Nd/¹⁴⁴Nd (0.512034) and ¹⁴⁷Sm/¹⁴⁴Nd (0.06357), as well as REE abundances, clarify provenance from upper crust sediments for samples with U/Pb age of 121–314 ka from the Ala-Tau range in the Urals. However, the morphology of flanged button shapes, ring waves, and eccentro-radiating ridges reliably constrains the origin of silicide spherules to distal meteoritic impact ejecta. Arc jet ablation experiments have previously demonstrated that similar morphologies, observed on australite tektites, reflect aerodynamic ablation rates corresponding to flight velocities well into orbital range. These features are generally accepted as conclusive evidence for hypervelocity atmospheric entry from space. Internal structure, consistent with accretion through the coalescence of 3–5 µm droplets, and composition, closely corresponding to 1893–1154 K span of C-type condensation sequences, indicate a high probability of processing through recondensation of ejecta vapor.

中文翻译：

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对超高温远侧撞击抛射物中硅化铁球粒起源的限制

地球上存在的硅化铁球粒在地质文献中描述了 160 年的宇宙起源并于 1984 年被 IMA CNMMN 批准为“外星”矿物，到目前为止还没有受到陨石学家的任何认真检查。我们首次获得的硅化物球粒的同位素和稀土元素数据与来自两大洲的古培岩 (Fe ₃ Si) 和西峰岩 (Fe ₅ Si ₃ ) 球粒的陨石起源不一致。尽管偏离了陆地规范 ( ⁸⁷ Rb/ ⁸⁶ Sr—0.0174; ⁸⁷ Sr/ ⁸⁶ Sr—0.700181; ³ He/ ⁴ He—7.57 × 10 ^-6 ; ⁴⁰ Ar/ ³⁶Ar—325.9)，¹⁴³ Nd/ ¹⁴⁴ Nd (0.512034) 和¹⁴⁷ Sm/ ¹⁴⁴的成分Nd (0.06357) 以及 REE 丰度，阐明了来自乌拉尔 Ala-Tau 山脉的 U/Pb 年龄为 121-314 ka 的样品的上地壳沉积物的来源。然而，法兰按钮形状、环形波和偏心辐射脊的形态可靠地将硅化物小球的起源限制为远端陨石撞击喷射物。电弧射流烧蚀实验先前已经证明，在澳大利亚陨石上观察到的类似形态反映了与进入轨道范围的飞行速度相对应的空气动力学烧蚀率。这些特征通常被认为是从太空进入超高速大气层的确凿证据。内部结构，与通过 3-5 µm 液滴聚结产生的吸积一致，其成分与 C 型冷凝序列的 1893-1154 K 跨度密切对应，