Extinct spreading center in the Labrador Sea: Crustal structure from a two-dimensional seismic refraction velocity model
Extinct spreading center in the Labrador Sea: Crustal structure from a two-dimensional seismic refraction velocity model
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拉布拉多海的灭绝扩张中心：二维地震折射速度模型的地壳结构
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
K. Louden
中科院分区：
文献类型：
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作者：
J. Osler;K. Louden
拉布拉多海包含一个罕见的废弃洋中脊的例子，由于岩石圈板块扩张几何形状的变化，洋壳的活跃增生停止了。地震折射数据是沿沿着一条横穿灭绝扩张中心的线收集的。利用射线追踪和合成地震图技术对折射数据进行的二维分析显示，地壳厚度和速度相对于灭绝扩张中心的轴线存在重大变化。在灭绝的扩张中心，地壳厚度约为4公里，相比之下，5.5公里的侧翼。上地壳和下地壳的P波速度横向变化很大，在灭绝扩张中心内有明显的下降。低速度也观察到在最上地幔下面的灭绝扩张中心，并解释为热液蚀变的结果。异常低的地壳速度和地壳减薄归因于部分熔融供应的减少和灭绝前缓慢扩张速率下构造作用程度的增加。
The Labrador Sea contains a rare example of an abandoned mid-ocean ridge where active accretion of oceanic crust ceased due to a change in the spreading geometry of lithospheric plates. Seismic refraction data were collected along a line which transversely crosses the extinct spreading center. Two-dimensional analyses of the refraction data, using ray-tracing and synthetic seismogram techniques reveal major variations in crustal thickness and velocity in relation to the axis of the extinct spreading center. In the extinct spreading center, a crustal thickness of approximately 4 km is determined, compared with 5.5 km for the flanks. Substantial lateral variations in P wave velocities of the upper and lower crust are observed with a marked decrease within the extinct spreading center. Low velocities are also observed in the uppermost mantle underlying the extinct spreading center and are interpreted as being the result of hydrothermal alteration. The anomalously low crustal velocities and crustal thinning are attributed to a decreasing supply of partial melt and increasing degree of tectonism at the slow spreading rates preceding extinction.