Molybdenum (Mo) isotope ratios provide a potential means of tracing material recycling involved in subduction zone processes. However, the geochemical behavior of Mo in subducted oceanic crust remains enigmatic. We analyzed Mo isotope ratios of arc and back-arc basin lavas from the Mariana subduction zone (western Pacific Ocean), combining newly obtained element and Sr-Nd-Pb-Li isotope data to investigate subduction zone geochemical processes involving Mo. The Mo isotope ratios (δ98/95MoNIST3134; U.S. National Institute of Standards and Technology [NIST] Mo standard) of the volcanic rocks showed clear across-arc variations, decreasing with increasing depth to the Wadati-Benioff zone. The high δ98/95Mo values in the Mariana Islands (−0.18‰ to +0.38‰) correspond to high 87Sr/86Sr, low 143Nd/144Nd, and radiogenic Pb isotope ratios, suggesting that altered upper oceanic crust played an important role in the magma source. The low δ98/95Mo values in the Central Mariana Trough (−0.65‰ to −0.17‰) with mantle-like Sr-Nd-Pb but slightly low δ7Li values provide direct evidence for the contribution of deep recycled oceanic crust to the magma source of the back-arc basin lavas. The isotopically light Mo magmas originated by partial melting of a residual subducted slab (eclogite) after high degrees of dehydration and then penetrated into the back-arc mantle. This interpretation provides a new perspective with which to investigate the deep recycling of subducted oceanic lithosphere and associated magma petrogenesis.

中文翻译：

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Mo同位素的跨弧变化及其对弧后盆地火山岩源中俯冲洋壳的影响

钼 (Mo) 同位素比率提供了一种追踪俯冲带过程中涉及的材料回收的潜在手段。然而，Mo在俯冲洋壳中的地球化学行为仍然是个谜。我们分析了马里亚纳俯冲带（西太平洋）弧和弧后盆地熔岩的 Mo 同位素比率，结合新获得的元素和 Sr-Nd-Pb-Li 同位素数据，研究了涉及 Mo 的俯冲带地球化学过程。 Mo 同位素火山岩的比值（δ98/95MoNIST3134；美国国家标准与技术研究院 [NIST] Mo 标准）显示出明显的跨弧变化，随着到瓦达蒂-贝尼奥夫带深度的增加而减小。马里亚纳群岛的高 δ98/95Mo 值（-0.18‰ 至 +0.38‰）对应于高 87Sr/86Sr、低 143Nd/144Nd 和放射性铅同位素比率，表明改变的上大洋地壳在岩浆来源中发挥了重要作用。中马里亚纳海槽的低δ98/95Mo值（-0.65‰至-0.17‰）具有类似地幔的Sr-Nd-Pb但δ7Li值略低，为深部再循环洋壳对岩浆源的贡献提供了直接证据。弧后盆地熔岩。同位素轻 Mo 岩浆起源于高度脱水后残余俯冲板片（榴辉岩）的部分熔融，然后渗透到弧后地幔中。这种解释为研究俯冲海洋岩石圈的深层循环和相关的岩浆成岩作用提供了新的视角。17‰)具有类似地幔的Sr-Nd-Pb但δ7Li值略低，为深部再循环洋壳对弧后盆地熔岩岩浆源的贡献提供了直接证据。同位素轻 Mo 岩浆起源于高度脱水后残余俯冲板片（榴辉岩）的部分熔融，然后渗透到弧后地幔中。这种解释为研究俯冲海洋岩石圈的深层循环和相关的岩浆成岩作用提供了新的视角。17‰)具有类似地幔的Sr-Nd-Pb但δ7Li值略低，为深部再循环洋壳对弧后盆地熔岩岩浆源的贡献提供了直接证据。同位素轻 Mo 岩浆起源于高度脱水后残余俯冲板片（榴辉岩）的部分熔融，然后渗透到弧后地幔中。这种解释为研究俯冲海洋岩石圈的深层循环和相关的岩浆成岩作用提供了新的视角。