Corrugated slip surfaces formed at ridge-transform intersections on the Mid-Atlantic Ridge
Corrugated slip surfaces formed at ridge-transform intersections on the Mid-Atlantic Ridge
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DOI：
10.1038/385329a0
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发表时间：
1997-01-23
期刊：
影响因子：
64.8
通讯作者：
Escartin, J
中科院分区：
文献类型：
--
作者：
Cann, JR;Blackman, DK;Escartin, J
在大西洋中脊的转换偏移和非转换偏移的内角形成的海洋地壳条带被地形高点（“内角高点”）打断，这里经常发现深成岩（包括辉长岩和橄榄岩）(4,5)。目前的构造模型认为内角高点是下地壳和上地幔物质，这些物质是由从内角倾斜到山脊轴下方的低角度滑脱断层挖出的(3,6-8)。但迄今为止，证明此类缺陷存在的大部分证据都是间接的。在这里，我们展示了大西洋中脊（北纬 30 度附近）上两个山脊变换交叉点的声纳图像，这些图像显示活跃的和“化石”的内角高点都被平坦的、倾斜的表面所覆盖，表面上有平行于板块扩张方向的波纹和条纹。尽管这些表面可能是模型所设想的低角度脱离断层，但它们的倾斜角度比预期的要浅得多。这可以通过蛇纹石化橄榄岩的润滑存在来解释，其碎片已从两个表面挖出。或者，这些滑动面可能代表蛇纹石润滑滑坡区的破坏面。
The strips of ocean crust formed at the inside corners of both transform and non-transform offsets on the Mid-Atlantic Ridge are punctuated by topographic highs-the 'inside-corner highs'(1-3)-where plutonic rocks (including gabbros and peridotites) are frequently found(4,5). Current tectonic models consider the inside-corner highs to be lower-crust and upper-mantle materials that have been exhumed by low-angle detachment faults dipping away from the inside corner to beneath the ridge axis(3,6-8). But much of the evidence for the existence of such faults has hitherto been circumstantial. Here we present sonar images of two ridge-transform intersections on the Mid-Atlantic Ridge (near 30 degrees N), which show that both active and 'fossil' inside-corner highs are capped by planar, dipping surfaces marked by corrugations and striations oriented parallel to the plate spreading direction. Although these surfaces may be the low-angle detachment faults envisaged by the models, they dip at much shallower angles than expected. This could be explained by the lubricating presence of serpentinized peridotite, fragments of which have been dredged from both surfaces. Alternatively, these slip surfaces may instead represent failure surfaces in serpentine-lubricated landslide zones.