Imaging continental breakup using teleseismic body waves: The Woodlark Rift, Papua New Guinea
Imaging continental breakup using teleseismic body waves: The Woodlark Rift, Papua New Guinea
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DOI：
10.1002/2015gc005835
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发表时间：
2015-09-01
影响因子：
3.5
通讯作者：
Jin, Ge
中科院分区：
文献类型：
--
作者：
Eilon, Zachary;Abers, Geoffrey A.;Jin, Ge
这项研究的图像下的D 'Entrecasteax群岛，巴布亚新几内亚的上地幔，提供了深入了解地幔变形下的一个高度裂谷大陆邻近传播扩张中心。利用2010-2011年CDPapua被动地震实验中记录的P波和S波地震的差走时反演大陆裂谷的独立V-P和V-S速度模型。低速结构标志着裂谷的东西轴，与最薄的地壳，高热流和线性趋势的火山有关。这个缓慢的区域从大洋扩张中心沿走向沿着250公里，表明在海底破裂之前有明显的地幔伸展。裂谷仍然狭窄的深度指示局部的扩展，可能是由于地幔水合作用。在台阵北部90-120公里深处的一个高V-P结构比裂谷轴快6.5%以上，并包含位置良好的中深度地震。这些独立的观测结果对裂谷轴和北部冷岩石圈之间深度的横向热对比产生了严格的限制，这可能与最近的俯冲有关，尽管俯冲的极性无法解决。这种几何形状在重力作用下是不稳定的;下沉流或小规模对流可能促进了裂谷和岩石圈的快速移动，尽管这可能需要一个湿地幔才能在所需的时间尺度上是现实的。高V结构与裂谷轴上出露的年轻超高压岩石记录的最大P、T条件一致，可能与它们的成因有关。
This study images the upper mantle beneath the D'Entrecasteax Islands, Papua New Guinea, providing insight into mantle deformation beneath a highly rifted continent adjacent to propagating spreading centers. Differential travel times from P and S-wave teleseisms recorded during the 2010-2011 CDPapua passive seismic experiment are used to invert for separate V-P and V-S velocity models of the continental rift. A low-velocity structure marks the E-W axis of the rift, correlating with the thinnest crust, high heat flow, and a linear trend of volcanoes. This slow region extends 250 km along strike from the oceanic spreading centers, demonstrating significant mantle extension ahead of seafloor breakup. The rift remains narrow to depth indicating localization of extension, perhaps as a result of mantle hydration. A high-V-P structure at depths of 90-120 km beneath the north of the array is more than 6.5% faster than the rift axis and contains well-located intermediate depth earthquakes. These independent observations place firm constraints on the lateral thermal contrast at depth between the rift axis and cold lithosphere to the north that may be related to recent subduction, although the polarity of subduction cannot be resolved. This geometry is gravitationally unstable; downwelling or small-scale convection could have facilitated rifting and rapid lithospheric removal, although this may require a wet mantle to be realistic on the required time scales. The high-V structure agrees with the maximum P, T conditions recorded by young ultra-high pressure rocks exposed on the rift axis and may be implicated in their genesis.