Abstract The accretionary mobile belts surrounding ancient cratonic cores are an important facet of the growth and preservation of continental landmasses. Peridotites from Nuominhe in the Xing'an Mongolia Orogenic Belt (XMOB) provide an additional opportunity to examine the age, structure and evolution of mantle lithosphere separating two of the largest existing ancient continental nuclei: the North China Craton and the Siberian Craton. This suite of mantle rocks comprises fertile to refractory garnet- and spinel-facies harzburgites and lherzolites. Their lithophile element systematics show that the peridotites were metasomatized to variable extent by silicate‑carbonate melts. Despite this, the highly siderophile element and Os isotope systematics appear to have been largely undisturbed. The Nuominhe peridotites have Re-depletion Os model ages (TRD) that range from 0.5 Ga to 2.4 Ga, with three peaks/major ranges at ~2.0–2.4 Ga, ~1.4–1.5 Ga and ~ 0.8 Ga, of which the latter two are closely similar to those data from other XMOB localities reported in the literature. The only section of the mantle that appears to have ages which correlate with crust formation is the suite with Neoproterozoic (~0.8 Ga) depletion ages, while the older mantle domains document older episodes of mantle depletion. Given the lack of correlation between equilibrium temperatures and bulk composition or TRD ages, the Nuominhe peridotites were inter-mixed in the mantle column, most likely as a result of incorporation of recycled older continental mantle fragments into juvenile Neoproterozoic mantle during the orogenic processes responsible for new lithosphere formation. Geothermobarometry of the Nuominhe peridotites indicates a conductive geotherm of ~60 mWm−2 and therefore a lithosphere thickness of ~125 km, which is thicker than most Phanerozoic continental terranes, and even thicker than Proterozoic regions that comprise the larger cratonic unit of the Siberian craton. This thick Proterozoic lithosphere sandwiched between the converging North China and Siberian cratons was evidently partly constructed from recycled refractory continental mantle fragments, perhaps extant in the convecting mantle, or in-part derived from the surrounding cratons, leading to a composite nature of the mantle in this re-healed continental suture. Re-accretion of recycled refractory old continental mantle fragments plays a significant role in affecting mantle composition and controlling the thickness of circum-cratonic landmasses between cratonic blocks.

中文翻译：

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环克拉通造山带下岩石圈根系的结构与演化——兴安蒙古造山带及其与华北和西伯利亚克拉通根系的关系

摘要 围绕古克拉通核心的增生移动带是大陆地块生长和保存的一个重要方面。来自兴安蒙古造山带 (XMOB) 诺民河的橄榄岩提供了一个额外的机会来研究地幔岩石圈的年龄、结构和演化，这些岩石圈将两个现存的最大古大陆核分开：华北克拉通和西伯利亚克拉通。这组地幔岩石包括肥沃到难熔的石榴石和尖晶石相的斜方辉石和锂辉石。他们的亲石元素系统学表明橄榄岩在不同程度上被硅酸盐-碳酸盐熔体交代。尽管如此，高度亲铁元素和 Os 同位素系统学似乎基本上没有受到干扰。诺敏河橄榄岩的再耗竭 Os 模型年龄 (TRD) 范围从 0.5 Ga 到 2.4 Ga，在~2.0-2.4 Ga、~1.4-1.5 Ga 和~0.8 Ga 三个峰值/主要范围，其中后两个与文献中报道的其他 XMOB 地区的数据非常相似。似乎具有与地壳形成相关的年龄的唯一地幔部分是具有新元古代 (~0.8 Ga) 耗竭年龄的套件，而较旧的地幔域记录了较早的地幔耗竭事件。由于平衡温度与整体成分或 TRD 年龄之间缺乏相关性，诺民河橄榄岩在地幔柱中相互混合，最有可能是由于在造山过程中导致新的岩石圈形成，回收的较旧大陆地幔碎片并入新生的新元古代地幔。诺民河橄榄岩的地温气压测量显示约 60 mWm-2 的导电地热，因此岩石圈厚度约 125 km，比大多数显生宙大陆地体更厚，甚至比包含西伯利亚克拉通更大克拉通单元的元古代地区更厚. 这个厚厚的元古代岩石圈夹在会聚的华北和西伯利亚克拉通之间，显然部分由回收的耐火大陆地幔碎片构成，可能存在于对流地幔中，或者部分来自周围的克拉通，在这个重新愈合的大陆缝合线中导致地幔的复合性质。再生耐火古老大陆地幔碎片的再增生在影响地幔成分和控制克拉通地块之间的环克拉通陆块厚度方面起着重要作用。