Abstract Luqu harzburgites from the Xigaze ophiolites represent ultra-refractory mantle domains in the Yarlung-Tsangbo Suture Zone, which is accepted as relics of the Neo-Tethys. These ultra-depleted harzburgites provide an excellent opportunity to constrain the ophiolite generation from the perspectives of Re-Os isotopes and highly siderophile elements. The depleted HSE patterns of several samples suggest that these harzburgites had experienced higher extents of partial melting than the normal abyssal peridotites. These conclusions were also evidenced by the petrological observations, such as the low modal contents of clinopyroxenes and the rare occurrence of residual sulfides. Re-depleted model ages (TRD) of two Luqu harzburgites with ultra-low absolute Re abundances yield an estimate of ca. 2.0 Ga for an ancient melting event, which implies that the Luqu peridotites have ancient domains. Even though the compositions of IPGE (Os, Ir, and Ru) in all Luqu samples are quite homogeneous and comparable to those of the primitive upper mantle (PUM), the variations of PPGE (Pt and Pd) and Re indicate that the Luqu harzburgites had experienced late-stage melt-rock interaction. These infiltrating melts are constrained to be silica-rich and sulfur-saturated and might be different from the melt accounted for the metasomatic clinopyroxene. The sulfide-rich melt agents are speculated to be derived from recycling ancient components, which is supported by several samples with elevated 187Os/188Os compositions and enriched Re abundances. Considering the dynamic environments and evolution history of the Neo-Tethys, these ultra-depleted mantle domains represented by Luqu harzburgites are readily formed by multi-stage processes of partial melting and melt-rock interactions in the mid-ocean ridges. Also, fragments of ancient subducted oceanic slabs within the mantle probably provide the sources of the recycling melts pervasive in the Xigaze mantle.

中文翻译：

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新特提斯的非均质亚脊地幔：日喀则蛇绿岩 Re Os 同位素和 HSE 组成的约束

摘要 日喀则蛇绿岩中的芦曲菱镁矿代表了雅鲁藏布江缝合带的超难熔地幔域，被认为是新特提斯纪的遗迹。从 Re-Os 同位素和高度亲铁元素的角度来看，这些超贫化的菱镁矿提供了一个极好的机会来限制蛇绿岩的生成。几个样品的贫化 HSE 模式表明，这些方铅矿比正常的深海橄榄岩经历了更高程度的部分熔融。这些结论也得到了岩石学观察的证实，例如单斜辉石的低模态含量和罕见的残留硫化物。两个具有超低 Re 绝对丰度的 Luqu 菱镁矿的再耗尽模型年龄 (TRD) 产生了大约 2.0 Ga 对于古老的融化事件，这意味着芦曲橄榄岩具有古老的领域。尽管所有鲁曲样品中 IPGE（Os、Ir 和 Ru）的成分非常均匀并且与原始上地幔（PUM）的成分相当，但 PPGE（Pt 和 Pd）和 Re 的变化表明鲁曲菱镁矿经历了晚期熔岩相互作用。这些渗透熔体被限制为富含二氧化硅和硫饱和，并且可能不同于交代单斜辉石的熔体。据推测，富含硫化物的熔融剂来自回收的古老成分，这得到了几个具有升高的 187Os/188Os 成分和富集 Re 丰度的样品的支持。考虑到新特提斯的动态环境和演化历史，这些以芦曲菱镁矿为代表的超贫化地幔域很容易通过大洋中脊部分熔融和熔岩相互作用的多阶段过程形成。此外，地幔内的古代俯冲大洋板块碎片可能是日喀则地幔中普遍存在的再循环熔体的来源。