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首页> 外文期刊>Geochemistry, geophysics, geosystems >Geochemical variations in Japan Sea back-arc basin basalts formed by high-temperature adiabatic melting of mantle metasomatized by sediment subduction components
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Geochemical variations in Japan Sea back-arc basin basalts formed by high-temperature adiabatic melting of mantle metasomatized by sediment subduction components

机译：沉积物俯冲成分交代的地幔高温绝热融化形成的日本海后弧盆地玄武岩的地球化学变化

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摘要

The Yamato Basin in the Japan Sea is a back-arc basin characterized by basaltic oceanic crust that is twice as thick as typical oceanic crust. Two types of ocean floor basalts, formed during the opening of the Japan Sea in the Middle Miocene, were recovered from the Yamato Basin during Ocean Drilling Program Legs 127/128. These can be considered as depleted (D-type) and enriched (E-type) basalts based on their incompatible trace element and Sr-Nd-Pb-Hf isotopic compositions. Both types of basalts plot along a common mixing array drawn between depleted mantle and slab sediment represented by a sand-rich turbidite on the Pacific Plate in the NE Japan fore arc. The depleted nature of the D-type basalts suggests that the slab sediment component is nil to minor relative to the dominant mantle component, whereas the enrichment of all incompatible elements in the E-type basalts was likely caused by a large contribution of bulk slab sediment in the source. The results of forward model calculations using adiabatic melting of a hydrous mantle with sediment flux indicate that the melting conditions of the source mantle for the D-type basalts are deeper and hotter than those for the E-type basalts, which appear to have formed under conditions hotter than those of normal mid-oceanic ridge basalts (MORB). These results suggest that the thicker oceanic crust was formed by greater degrees of melting of a hydrous metasomatized mantle source at unusually high mantle potential temperature during the opening of the Japan Sea.
机译：日本海的大和盆地是一个弧后盆地，其特征是玄武质洋壳的厚度是典型洋壳的两倍。在中新世中期日本海开放期间形成的两种海底玄武岩，是在《远洋钻探计划》第127/128号法律程序中从大和盆地中回收的。基于它们不相容的痕量元素和Sr-Nd-Pb-Hf同位素组成，它们可以被视为贫化（D型）和富化（E型）玄武岩。两种类型的玄武岩都沿着在日本东北前太平洋太平洋板块中由富砂浊石代表的贫化地幔和板状沉积物之间绘制的共同混合阵列绘制。 D型玄武岩的枯竭性质表明，板状沉积物组分相对于占主导地位的地幔组分几乎为零，而E型玄武岩中所有不相容元素的富集可能是由于散装板状沉积物的大量贡献所致在源中。使用含沉积物通量的含水地幔的绝热融化进行的正向模型计算结果表明，D型玄武岩的源地幔融化条件比E型玄武岩的地幔融化条件更深，更热。条件比正常的洋中脊玄武岩（MORB）炎热。这些结果表明，在日本海开放期间，在异常高的地幔潜能温度下，含水交代的地幔源的熔融程度更高，形成了较厚的海洋地壳。

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