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首页> 外文期刊>Geochemistry, geophysics, geosystems >Propagation of back-arc extension into the arc lithosphere in the southern New Hebrides volcanic arc
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Propagation of back-arc extension into the arc lithosphere in the southern New Hebrides volcanic arc

机译：后弧扩展向新赫布里底火山弧南部的弧形岩石圈传播

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摘要

New geophysical data acquired during three expeditions of the R/V Southern Surveyor in the southern part of the North Fiji Basin allow us to characterize the deformation of the upper plate at the southern termination of the New Hebrides subduction zone, where it bends eastward along the Hunter Ridge. Unlike the northern end of the Tonga subduction zone, on the other side of the North Fiji Basin, the 908 bend does not correspond to the transition from a subduction zone to a transform fault, but it is due to the progressive retreat of the New Hebrides trench. The subduction trench retreat is accommodated in the upper plate by the migration toward the southwest of the New Hebrides arc and toward the south of the Hunter Ridge, so that the direction of convergence remains everywhere orthogonal to the trench. In the back-arc domain, the active deformation is characterized by propagation of the back-arc spreading ridge into the Hunter volcanic arc. The N-S spreading axis propagates southward and penetrates in the arc, where it connects to a sinistral strike-slip zone via an oblique rift. The collision of the Loyalty Ridge with the New Hebrides arc, less than two million years ago, likely initiated this deformation pattern and the fragmentation of the upper plate. In this particular geodynamic setting, with an oceanic lithosphere subducting beneath a highly sheared volcanic arc, a wide range of primitive subduction-related magmas has been produced including adakites, island arc tholeiites, back-arc basin basalts, and medium-K subduction-related lavas.
机译：在北斐济盆地南部进行的R / V南部测量师三次考察中获得的新地球物理数据使我们能够表征新赫布里底俯冲带南端的上板块的变形，沿该板块向东弯曲。猎人岭。与汤加俯冲带的北端不同，在北斐济盆地的另一侧，908弯道并不对应于从俯冲带到转换断层的过渡，但这是由于新赫布里底群岛的逐渐退缩沟。通过向新赫布里底弧的西南方向和向亨特山脊的南部的迁移，俯冲槽的后退部分被容纳在上板中，因此会聚方向始终保持与槽正交。在后弧域，主动变形的特征在于后弧扩展脊向亨特火山弧传播。 N-S传播轴向南传播并穿透弧线，在该弧线上它通过倾斜裂谷连接到左旋走滑带。不到200万年前，忠诚山脊与新赫布里底弧的碰撞很可能引发了这种变形模式和上板块的破碎。在这种特殊的地球动力学环境中，海洋岩石圈在高剪切火山弧下俯冲，产生了大量与俯冲有关的原始岩浆，包括ad石，岛弧冲孔岩，弧后盆地玄武岩以及与中钾俯冲有关的岩浆。熔岩。

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