The unusually prolonged volcanism at the Chang'e-5 (CE-5) landing site remains a mystery. To constrain the geochemical features of the CE-5 mantle source, we performed in situ sulfur isotope analysis on sulfides of the CE-5 basalts. The modal abundance of sulfides is ∼0.1 wt%, dominated by troilite with trace cubanite, chalcopyrite and pentlandite, yielding a S-abundance of ∼360 ± 180 ppm for the bulk CE-5 basalts. Our analysis shows a decreasing trend of δ³⁴S in the magma with crystallization and degassing, suggesting ∼40% degassing loss of S, and accordingly the maximum S-abundance in CE-5 primitive magma was calibrated to approximately 600 ± 300 ppm. Considering an extensive fractional crystallization following a low-degree partial melting of the CE-5 basalts, the estimated sulfur abundance in the mantle source is ∼1–10 ppm. This result suggests a strong depletion of volatiles in the CE-5 mantle source, which may be caused by prolonged magmatic activity.

中文翻译：

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嫦娥五号最年轻玄武岩的硫同位素分馏：对岩浆脱气和地幔源地球化学特征的约束

嫦娥五号（CE-5）着陆点异常长时间的火山活动仍然是一个谜。为了限制 CE-5 地幔源的地球化学特征，我们对 CE-5 玄武岩的硫化物进行了原位硫同位素分析。硫化物的模态丰度约为 0.1 wt%，主要是含有痕量立方铜矿、黄铜矿和镍铬铁矿的陨石，对于散装 CE-5 玄武岩，产生的S 丰度约为 360 ± 180 ppm。我们的分析显示 δ ^{34呈下降趋势}岩浆中的 S 结晶和脱气，表明 S 的脱气损失约为 40%，因此 CE-5 原始岩浆中的最大 S 丰度被校准为大约 600 ± 300 ppm。考虑到 CE-5 玄武岩的低度部分熔融后广泛的分级结晶，估计地幔源中的硫丰度约为 1-10 ppm。这一结果表明 CE-5 地幔源中挥发物的强烈消耗，这可能是由长时间的岩浆活动引起的。