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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Subduction zone dynamics in the SW Pacific plate boundary region constrained from high-precision Pb isotope data
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Subduction zone dynamics in the SW Pacific plate boundary region constrained from high-precision Pb isotope data

机译：高精度Pb同位素数据限制了西南太平洋板块边界区域的俯冲带动力学

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This study presents high-precision Pb isotope data obtained by MC-ICP-MS for lavas from the Solomon island arc that covers ca. 1000km of the SW Pacific plate boundary. Following a reversal of subduction polarity, the presence of the old subducted Pacific oceanic crust, and the presently subducting Indian-Australian plate beneath the entire island arc is confirmed by geophysical and geochemical evidence. New high-precision Pb isotope data now permit to distinguish more clearly between Indian and Pacific-type subduction components in this complex plate tectonic constellation. The values range from ~(206)Pb/~(204)Pb=18.345 to 18.845, ~(207)Pb/~(204)Pb=15.498 to 15.545, and ~(208)Pb/~(204)Pb=38.120 to 38.372, indicating the absence of pelagic sediments in the sub-arc mantle. These data reveal a predominance of subduction components derived from ancient subduction of the Pacific plate. In contrast, lavas with Indian-type Pb isotope signatures are confined to the central New Georgia Group of the Solomon Islands, where the young Woodlark Ridge spreading centre is currently subducting. All other Solomon arc segments with a lower geothermal gradient have apparently not yet been overprinted by younger subduction components over the past 6Myrs. Moreover, trace element and Pb isotope data for Woodlark Ridge basalts show that subduction components from the fossil Pacific slab have locally modified the source of Woodlark Basin lavas. Altogether, our study highlights the potential of high-resolution Pb isotope measurements to distinguish between Indian and Pacific-type subduction components along the SW Pacific plate boundary.
机译：这项研究提供了通过MC-ICP-MS获得的所罗门群岛弧覆盖的熔岩的高精度Pb同位素数据。西南太平洋板块边界的1000公里。在俯冲极性反转之后，地球物理和地球化学证据证实了旧俯冲太平洋洋壳的存在，以及整个岛弧下方目前俯冲的印度-澳大利亚板块的存在。现在，新的高精度Pb同位素数据可以更清楚地区分此复杂板块构造星座中的印度型和太平洋型俯冲成分。值的范围是〜（206）Pb /〜（204）Pb = 18.345至18.845，〜（207）Pb /〜（204）Pb = 15.498至15.545和〜（208）Pb /〜（204）Pb = 38.120到38.372，表明在弧下地幔中没有浮游沉积物。这些数据表明，俯冲成分主要来自太平洋板块的古代俯冲。相比之下，具有印度型Pb同位素特征的熔岩则局限于所罗门群岛的新乔治亚州中部地区，年轻的Woodlark Ridge扩散中心目前正在俯冲。在过去的6Myrs中，地热梯度较低的所有其他所罗门弧段显然还没有被较年轻的俯冲分量覆盖。此外，Woodlark Ridge玄武岩的痕量元素和Pb同位素数据表明，化石太平洋板块的俯冲成分已局部改变了Woodlark盆地熔岩的来源。总之，我们的研究强调了高分辨率Pb同位素测量在区分西南太平洋板块边界沿印度和太平洋俯冲成分方面的潜力。

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