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首页> 外文期刊>Geochemistry, geophysics, geosystems >Crust and upper mantle structure associated with extension in the Woodlark Rift, Papua New Guinea from Rayleigh-wave tomography
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Crust and upper mantle structure associated with extension in the Woodlark Rift, Papua New Guinea from Rayleigh-wave tomography

机译：瑞利波层析成像与巴布亚新几内亚伍德拉克裂谷伸展相关的地壳和上地幔结构

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摘要

The Woodlark seafloor spreading center is propagating westward into the Australian plate near the D'Entrecasteaux Islands (DI), Papua New Guinea, generating an active transition zone from continental rifting to seafloor spreading. From March 2010 to July 2011, we deployed 31 on-shore and 8 offshore broadband seismic stations around the DI region, to explore the dynamic processes of the lithosphere extension and the exhumation of the high-pressure terranes exposed on those islands. We measure the multiband (10-60 s) Rayleigh-wave phase velocities from both ambient noise and earthquake signals. These measurements are then inverted for a three-dimensional shear-velocity model for the crust and upper mantle. The results indicate that the lithosphere extension is localized near the rift axis beneath the DI, with a shear-velocity structure in the upper mantle that is similar to mid-ocean ridges. Beneath the Kiribisi Basin west of DI, an ultraslow shear-velocity anomaly (similar to 4.0 km/s) is observed at shallow mantle depth (30-60 km), which can be interpreted either by the presence of excess partial melt due to slow melt extraction, or by the existence of felsic crustal material buried to mantle depth and not yet exhumed.
机译：伍德拉克海底扩散中心正在向西传播到巴布亚新几内亚的德恩斯特卡斯特群岛（DI）附近的澳大利亚板块，形成了一个从大陆裂谷到海底扩散的活跃过渡带。从2010年3月到2011年7月，我们在DI地区周围部署了31个陆上和8个海上宽带地震台站，以探索岩石圈扩展的动态过程以及暴露在这些岛屿上的高压地层的挖掘。我们从环境噪声和地震信号中测量多频带（10-60 s）瑞利波相位速度。然后，将这些测量结果进行反演，以建立针对地壳和上地幔的三维剪切速度模型。结果表明，岩石圈扩展区位于DI下方的裂谷轴附近，上地幔中的剪切速度结构类似于中海脊。在DI以西的基里比斯盆地之下，在浅地幔深度（30-60 km）处观察到了超慢的剪切速度异常（类似于4.0 km / s），这可以解释为由于慢速而存在过量的局部融化。熔体提取，或由于存在于地幔深处而尚未挖掘的长英质地壳物质的存在。

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