Local lithospheric relief associated with fracture zones and ponded plume material
Local lithospheric relief associated with fracture zones and ponded plume material
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DOI：
10.1029/2002gc000376
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发表时间：
2002-12
期刊：
影响因子：
3.7
通讯作者：
N. Sleep
中科院分区：
文献类型：
--
作者：
N. Sleep
海洋岩石圈底部的浮力羽流物质池。由于板块年龄，它是岩石圈底部地形的天然探针，因为它沿着颠倒的排水模式横向流动。正如预期的那样，对洋脊附近和洋脊上热点的地貌和地球化学研究表明，海洋岩石圈随着年龄的增长而增厚。薄岩石圈走廊沿轴线引导羽流物质，而山脊部分末端的厚岩石圈则阻挡了这种沿轴线的流动。通道热点从羽流向山脊轴延伸。然而，在旧洋盆内的断裂带，当地岩石圈厚度和当地年龄之间的良好相关性并不明显。如果岩石圈仅通过传导冷却，则可以预期这种相关性。然后，压力释放熔融和火山将优先发生在断裂带附近，在断裂带处，羽状物质从厚的旧岩石圈瀑布流到薄的年轻岩石圈。这种火山建筑物的集中度并没有发生。岩石圈厚度和板块年龄之间缺乏相关性是岩石圈底部小规模对流的预期结果。比例关系和数值模型表明，每平方米几毫瓦的适度剧烈对流足以扰动断裂带下方的局部岩石圈起伏，而不改变岩石圈厚度与板块年龄的总体相关性。通常，岩石圈厚度的台阶向断裂带的旧侧移动。
Buoyant plume material ponds at the base of oceanic lithosphere. It is a natural probe for the relief on the base of the lithosphere owing to plate age because it flows laterally along an upside‐down drainage pattern. Geomorphic and geochemical studies of near‐ridge and on‐ridge hot spots indicate, as expected, that the oceanic lithosphere thickens as it ages. Corridors of thin lithosphere channel plume material along the axis, while the thick lithosphere at the end of ridge segments dams this along‐axis flow. Channel hot spots extend from plumes toward ridge axes. However, a good correlation between local lithospheric thickness and local age is not evident at fracture zones within the old ocean basins. Such a correlation would be expected if the lithosphere cooled only by conduction. Then pressure‐release melting and volcanoes would occur preferentially near fracture zones where plume material cascades from thick old to thin young lithosphere. This concentration of volcanic edifices does not occur. This lack of correlation between lithosphere thickness and plate age is an expected consequence of small‐scale convection at the base of the lithosphere. Scaling relationships and numerical models indicate that modestly vigorous convection of several milliwatt per meter squared is sufficient to perturb local lithospheric relief beneath fracture zones without changing the gross correlation of lithospheric thickness with plate age. Typically, the step in lithospheric thickness moves toward the old side of the fracture zone.