Sulfur Isotopic Fractionation of the Youngest Chang'e‐5 Basalts: Constraints on the Magma Degassing and Geochemical Features of the Mantle Source
Xiaoying Liu, Jialong Hao, Ruiying Li, Yuyang He, Heng‐Ci Tian, Sen Hu, Jing Li, Lixin Gu, Wei Yang, Yangting Lin
Abstract
Abstract 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 δ 34 S 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.