Abstract We have studied a suite of mantle zircons from several differently aged pipes of the Siberian kimberlite province via U Pb and Lu Hf isotope analyses and trace element compositions. The U Pb ages we obtained confirmed four main episodes (Silurian, Devonian, Triassic and Jurassic) of kimberlite activity on the Siberian craton. The Druzhba pipe had two populations of zircons dating from the Silurian and Devonian, respectively. The geochemical features of our suite of mantle zircons show low concentrations of U, Th and heavy rare earth elements (REEs), positive Ce anomalies, and weak or absent Eu anomalies, which is in accord with the mantle-derived nature of the zircon. Despite having broadly similar geochemistry, zircons from differently aged kimberlites had some clear differences arising from variations in the composition of the protokimberlite metasomatic melt and from peculiarities of fractional crystallization. The Th/U ratios were highest in the Silurian zircons and sharply decreased toward the Devonian. The Triassic zircons had elevated and highly variable Ce/Nb ratios with low and nearly constant Th/U ratios. Zircons from Siberian kimberlites with different U Pb ages showed systematic variations in their initial Hf isotope compositions. The oldest Silurian kimberlite field, Chomurdakh, had two zircon populations: Silurian zircons, with ɛHft values in the range of +2.8 to +5.9 units, and Devonian zircons, with ɛHft values in the range of +1.6 to +2.0 units. Zircons from the Devonian field kimberlites were in the range of +5.6 to +9.6 ɛHft units. The Triassic kimberlitic zircons had the most juvenile Hf isotope composition, at +9.3 to +11.2 ɛHft units, while the Jurassic zircons had +6.9 ɛHft units. The combination of the U Pb and Lu Hf isotope data suggests a periodic rejuvenation of the lithospheric mantle roots by low-volume melts from the asthenospheric mantle, resulting shortly after in kimberlite emplacements. Some Devonian and Jurassic kimberlites may have been melted by re-heating the Silurian and Triassic age sources, respectively, about 60 Myr after they were formed.

中文翻译：

---

源再生与再加热：来自 U Pb 和 Lu Hf 同位素组成和地幔锆石地球化学对西伯利亚金伯利岩成因的限制

摘要 我们通过 U Pb 和 Lu Hf 同位素分析和微量元素组成研究了来自西伯利亚金伯利岩省几个不同年龄的管子的一套地幔锆石。我们获得的 U Pb 年龄证实了西伯利亚克拉通上金伯利岩活动的四个主要事件（志留纪、泥盆纪、三叠纪和侏罗纪）。Druzhba 管道有两个锆石群，分别来自志留纪和泥盆纪。我们这组地幔锆石的地球化学特征显示出低浓度的 U、Th 和重稀土元素 (REE)，Ce 正异常，以及弱或不存在 Eu 异常，这与锆石的地幔衍生性质一致。尽管具有大致相似的地球化学，由于原始金伯利岩交代熔体成分的变化和分步结晶的特性，来自不同年龄的金伯利岩的锆石有一些明显的差异。Th/U 比值在志留系锆石中最高，在泥盆纪急剧下降。三叠纪锆石具有升高且高度可变的 Ce/Nb 比率，Th/U 比率低且几乎恒定。来自不同 U Pb 年龄的西伯利亚金伯利岩的锆石在其初始 Hf 同位素组成中表现出系统性变化。最古老的志留系金伯利岩油田 Chomurdakh 有两个锆石群：志留系锆石，其 ɛHft 值在 +2.8 至 +5.9 单位的范围内，以及泥盆纪锆石，其 ɛHft 值在 +1.6 至 +2.0 单位的范围内。泥盆纪领域金伯利岩的锆石在 +5.6 至 +9.6 ɛHft 单位的范围内。三叠纪金伯利岩锆石具有最年轻的 Hf 同位素组成，为 +9.3 至 +11.2 ɛHft 单位，而侏罗纪锆石具有 +6.9 ɛHft 单位。U Pb 和 Lu Hf 同位素数据的结合表明，来自软流圈地幔的低体积熔体使岩石圈地幔根部周期性恢复活力，并在不久之后形成金伯利岩侵位。一些泥盆纪和侏罗纪金伯利岩可能在它们形成后分别重新加热志留纪和三叠纪源约 60 密尔而熔化。U Pb 和 Lu Hf 同位素数据的结合表明，来自软流圈地幔的低体积熔体使岩石圈地幔根部周期性恢复活力，并在不久之后形成金伯利岩侵位。一些泥盆纪和侏罗纪金伯利岩可能在它们形成后分别重新加热志留纪和三叠纪源约 60 密尔而熔化。U Pb 和 Lu Hf 同位素数据的结合表明，来自软流圈地幔的低体积熔体使岩石圈地幔根部周期性恢复活力，并在不久之后形成金伯利岩侵位。一些泥盆纪和侏罗纪金伯利岩可能在它们形成后分别重新加热志留纪和三叠纪源约 60 密尔而熔化。