The asthenosphere beneath both ancient and modern oceans is highly heterogeneous owing to the recycling of continental, sub-arc, or sub-oceanic mantle domains and subducted oceanic crust and pelagic sediments. The identification and discrimination of those “old” mantle domains are important for understanding of the generation of oceanic crust and the tectonic setting of ophiolites. Here we report geochemical data including Re–Os and Lu–Hf isotopic compositions for mantle peridotites from the Kop Mountain ophiolite in the western Neo-Tethys. These peridotites have whole-rock and mineral compositions comparable with those of abyssal peridotites. Trace element modeling of clinopyroxenes indicates that they were subjected to anhydrous melting, and in this respect the rocks are distinguishable from supra-subduction zone peridotites. Re–Os and Lu–Hf isotopic compositions further indicate that these mantle peridotites underwent ancient (at or before 1.52 Ga) melt extraction and Jurassic melt metasomatism. The Kop Mountain mantle peridotites thus represent ancient sub-oceanic mantle domains recycled into the Neo-Tethyan asthenosphere, undergoing earlier melt depletion before being entrained at the Neo-Tethyan ridge axis. Our results, together with data published for other ophiolites, indicate that the Os isotopic distribution of the Neo-Tethyan ophiolites is identical to that of global abyssal peridotites, suggesting similar melting histories. The Neo-Tethyan asthenosphere was highly heterogeneous, probably with numerous recycled continental, sub-arc, and sub-oceanic mantle inputs. The recycling of ancient mantle in the asthenosphere could be an alternative explanation for the generation of anomalous compositions in both modern and ophiolitic oceanic crusts such as K-rich lavas, enriched mid-ocean ridge basalts, and arc-like basalts. The use of basalt geochemical data to discriminate between tectonic settings (i.e., mid-ocean ridge or supra-subduction zone) of ophiolites should thus be approached with caution.

由于大陆、亚弧或亚洋地幔域以及俯冲洋壳和远洋沉积物的再循环，古代和现代海洋下方的软流圈具有高度异质性。这些“旧”地幔域的识别和区分对于理解大洋地壳的形成和蛇绿岩的构造环境很重要。在这里，我们报告了来自新特提斯西部 Kop 山蛇绿岩的地幔橄榄岩的地球化学数据，包括 Re-Os 和 Lu-Hf 同位素组成。这些橄榄岩的全岩和矿物成分与深海橄榄岩相当。单斜辉石的微量元素模型表明它们经历了无水熔融，在这方面，这些岩石与超俯冲带橄榄岩是有区别的。Re-Os 和 Lu-Hf 同位素组成进一步表明，这些地幔橄榄岩经历了古老的（在 1.52 Ga 或之前）熔体提取和侏罗纪熔体交代作用。因此，科普山地幔橄榄岩代表了循环进入新特提斯软流圈的古老亚洋地幔域，在被卷入新特提斯洋脊轴之前经历了较早的熔体消耗。我们的研究结果以及其他蛇绿岩发表的数据表明，新特提斯蛇绿岩的 Os 同位素分布与全球深海橄榄岩的 Os 同位素分布相同，表明具有相似的熔化历史。新特提斯软流圈是高度异质的，可能有许多再循环的大陆、亚弧和亚洋地幔输入。软流圈中古代地幔的再循环可能是现代和蛇绿质洋壳中异常成分的产生的另一种解释，例如富含钾的熔岩、富集的洋中脊玄武岩和弧形玄武岩。因此，应谨慎使用玄武岩地球化学数据来区分蛇绿岩的构造环境（即大洋中脊或俯冲带）。