Molybdenum isotope is a diagnostic tracer for crustal and mantle components in arc magmatism. However, the mechanism of Mo isotopic variation in arc magmas is still debated, e.g., input of different subduction components into the mantle wedge versus isotopic fractionation during dehydration of subducted slab. Here we present whole-rock Mo-Sr-Nd-Hf-Pb isotopic data for the Continental Arc Basalt (CAB) and Back Arc Basalt (BAB) from Java, Indonesia, to investigate the role of slab inputs in Mo isotopic variation of the Sunda arc magmatism. The CAB samples have variable K₂O contents (0.44–2.49 wt%) and are mainly classified as calc-alkaline series, while the BAB samples are shoshonitic with markedly high K₂O contents (2.12–6.90 wt%) relative to the CABs. The Java CABs and BABs have similar Mo isotopic compositions (δ^98/95Mo = -0.65 to -0.07‰ and -0.66 to -0.07‰, respectively, relative to NIST SRM3134), suggesting that such a significant Mo isotopic variation should not be caused solely by the isotopic fractionation during the subduction. Instead, δ^98/95Mo values of the Java basalts positively correlate with Pb isotopic ratios. This implies that the Mo isotopic variations in the Java arc rocks should result from the metasomatism in the mantle wedge by hybrid agents, including varying proportions of melts from subducted sediments (with heavy Mo isotope) and melts from the subducted altered upper oceanic crust (SAOC) (with light Mo isotope). The light Mo isotope of the Java arc rocks, compared with the Mariana arc basalts, suggests that melts from the SAOC have much lighter Mo isotopic compositions than the components from the lower oceanic crust. Thus, Mo isotope has great potential to distinguish the components from the subducted upper and lower oceanic crust. The Java CABs show along-arc variations in Mo-Sr-Nd-Hf-Pb isotopes, which is related closely with the thermal status of the subducted slab. Upwelling of the asthenosphere due to the slab tearing beneath the Java arc might have enhanced the partial melting of subducted sediments nearby the slab window. The complicated subduction system in the Sunda arc has strongly controlled the geochemical composition of arc magmas, which changes with input of different subduction components into the mantle wedge along arc.

钼同位素是弧形岩浆作用中地壳和地幔成分的诊断示踪剂。然而，弧岩浆中钼同位素变化的机制仍存在争议，例如俯冲板片脱水过程中不同俯冲成分输入地幔楔与同位素分馏。在这里，我们提供了来自印度尼西亚爪哇的大陆弧玄武岩 (CAB) 和弧后玄武岩 (BAB) 的全岩 Mo-Sr-Nd-Hf-Pb 同位素数据，以研究板片输入在 Mo 同位素变化中的作用。巽他弧岩浆作用。CAB 样品具有可变的 K ₂ O 含量（0.44-2.49 wt%），主要归类为钙碱性系列，而 BAB 样品是具有显着高 K _{2的玄武岩。}相对于 CAB 的 O 含量（2.12-6.90 wt%）。Java CAB 和 BAB 具有相似的 Mo 同位素组成（相对于 NIST SRM3134，δ ^98/95 Mo = -0.65 至 -0.07‰ 和 -0.66 至 -0.07‰），这表明不应存在如此显着的 Mo 同位素变化完全由俯冲过程中的同位素分馏引起。相反，δ ^98/95爪哇玄武岩的 Mo 值与 Pb 同位素比呈正相关。这意味着爪哇弧岩中的钼同位素变化应该是由混合介质在地幔楔中的交代作用引起的，包括不同比例的俯冲沉积物熔体（含重钼同位素）和俯冲蚀变上洋壳熔体（SAOC） )（含轻钼同位素）。与马里亚纳弧玄武岩相比，爪哇弧岩的轻 Mo 同位素表明，来自 SAOC 的熔体的 Mo 同位素组成比来自下洋壳的成分轻得多。因此，Mo同位素在区分俯冲上、下洋壳的成分方面具有很大的潜力。Java CABs表现出Mo-Sr-Nd-Hf-Pb同位素的沿弧变化，这与俯冲板片的热状态密切相关。由于爪哇弧下方的板片撕裂导致的软流圈上涌可能增强了板片窗口附近俯冲沉积物的部分熔融。巽他弧复杂的俯冲系统强烈控制了弧岩浆的地球化学成分，随着不同俯冲成分沿弧线输入地幔楔而发生变化。