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首页> 外文期刊>Journal of Asian earth sciences >Age and geochemistry of volcanic clasts from DSDP Site 445, Daito Ridge and relationship to Minami-Daito Basin and early Izu-Bonin arc magmatism
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Age and geochemistry of volcanic clasts from DSDP Site 445, Daito Ridge and relationship to Minami-Daito Basin and early Izu-Bonin arc magmatism

机译：大东岭DSDP 445站火山碎屑的年龄和地球化学及其与南大同盆地和伊豆-波宁早期弧岩浆活动的关系

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The age and character of volcanism on the Daito Ridge is important for understanding the tectonic evolution of the Philippine Sea plate and the initiation of subduction that formed the Izu-Bonin-Mariana Island arc at about 50 Ma. We report new major, trace element and Nd, Sr, Pb and Hf isotope data for basaltic clasts from volcaniclastic sediments drilled at DSDP Site 445 on the Daito Ridge, and new Ar-Ar ages for minerals from the same location. Ages indicate that volcanic material in the core is as young as 47-49 Ma, similar in age to OIB-like basaltic sills from the adjacent Minami-Daito Basin and similar in age to the earliest volcanic rocks from the Izu-Bonin-Mariana (IBM) Island arc. The basaltic clasts have the major and trace element character of subduction-related rocks from mature island arc settings, and are unlike boninites or other rocks formed in proposed arc initiation sequences. Isotopic compositions are consistent with melting of mantle wedge with an Indian Ocean signature (i.e., elevated ~(208)Pb/~(204)Pb relative to ~(206)Pb/~(204)Pb and ~(177)Hf/~(176)Hf relative to ~(143)Nd/~(144)Nd), containing subduction components derived from seawater altered Pacific Ocean MORB. Isotopic compositions overlap with those for boninites from the early northern IBM arc, suggesting that extraction of arc magma during Cretaceous-Eocene magmatism on the Daito Ridge and adjacent remnant arcs in the northern Philippine Sea, formed part of the depleted mantle wedge that was remelted during the initiation of IBM arc magmatism. Based on tectonic models, the Daito arc mantle wedge was probably isolated and cut-off from volatile replenishment by the initiation of subduction along the orthogonal trend of the proto-IBM arc. Collision of the Oki Daito Ridge may also have contributed to the waning of arc volcanism on the Daito Ridge and the contemporaneous eruption of OIB-like basalts in the Minami-Daito Basin.
机译：大东岭上的火山活动的年龄和特征对于了解菲律宾海板块的构造演化以及在约50 Ma处形成伊豆-波宁-马里亚纳岛弧的俯冲作用起着重要作用。我们报告了在大东岭DSDP 445站钻探的火山碎屑沉积物中玄武岩碎屑的新的主要，微量元素和Nd，Sr，Pb和Hf同位素数据，以及同一地点的矿物的新Ar-Ar年龄。年龄表明，岩心中的火山物质年龄低至47-49 Ma，与邻近的南大同盆地的OIB类玄武岩基岩年龄相似，与伊豆-波宁-马里亚纳州最早的火山岩年龄相似（ IBM）岛屿弧。玄武岩碎屑具有成熟的岛弧环境中与俯冲有关的岩石的主要和微量元素特征，并且不同于在建议的弧起始序列中形成的邦尼石或其他岩石。同位素组成与具有印度洋特征的地幔楔融化一致（即，相对于〜（206）Pb /〜（204）Pb和〜（177）Hf /〜升高〜（208）Pb /〜（204）Pb （176）Hf相对于〜（143）Nd /〜（144）Nd），包含源自海水改变的太平洋MORB的俯冲分量。同位素组成与IBM北部早期弧线的硬质岩成分重叠，这表明在大东山脊白垩纪-始新世岩浆活动和菲律宾北部海域的相邻残余弧期间，弧岩浆的提取形成了贫化的地幔楔的一部分，在此期间IBM电弧岩浆作用的开始。基于构造模型，大都弧弧地幔楔可能是通过沿着原始IBM弧的正交趋势开始俯冲作用而被隔离的，并从挥发性补给中切断。 Oki Daito山脊的碰撞也可能导致了Daito山脊弧形火山活动的减弱，以及南大东盆地OIB类玄武岩的同期喷发。

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