Dynamics of sediment subduction, melange formation, and prism accretion
Dynamics of sediment subduction, melange formation, and prism accretion
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DOI：
10.1029/jb091ib10p10229
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发表时间：
1986-09
影响因子：
--
通讯作者：
R. L. Shreve;M. Cloos
中科院分区：
文献类型：
--
作者：
R. L. Shreve;M. Cloos
俯冲带中的下降板块和上覆块体类似滑靴轴承中的导向面和滑块，俯冲沉积物类似于润滑剂。然而，俯冲作用更为复杂和多样，因为上覆的块体不是刚性的，沉积物是浮力的，可能发生底沉积，沉积物的供应可能变化很大。一个基于方位类比但考虑到这些差异的模型对实际地点进行了详细的定量预测，这可以通过五个不同例子的计算来说明：马里亚纳，北纬16°；墨西哥,17°N;小安的列斯群岛，北纬13度（巴巴多斯）；阿拉斯加，西经153度（科迪亚克）；日本，北纬40度。它需要将上覆块体和下降板块顶部的几何形状、上覆块体的密度和渗透率分布、俯冲速度、俯冲沉积物的密度和流变性能以及沉积物输入速率作为输入。它的预测包括俯冲沉积层的厚度剖面（所有地点，马里亚纳最大360米，日本5300米），层内的流速（所有地点），施加在岩壁上的剪切应力（所有地点，在吸积柱之下较低，在日本之下可达6兆帕），剥落率(马里亚纳和晚第三纪墨西哥没有，小安的列斯群岛85%；包括混杂岩在日本的分布和速率（在马里亚纳没有，在日本广泛），可能的俯冲侵蚀带（在马里亚纳广泛，在其他地方局部），俯冲到火山弧的沉积物数量（所有地点；在小安的列斯占2%，在马里亚纳占100%），入口流动的质量模式（五种基本模式；所有地点），混合岩在许多情况下的向上流动(在马里亚纳没有；在日本广泛分布)，在相对罕见的条件下，形成了大型混杂底辟（只在巴巴多斯岛下面的小安的列斯群岛）。
The descending plate and overriding block in a subduction zone are analogous to the guide surface and slide block in a slipper bearing, and subducted sediment is analogous to the lubricant. Subduction is more complex and varied, however, because the overriding block is not rigid, the sediment is buoyant, underplating can occur, and sediment supply can vary widely. A model based on the bearing analogy but taking these differences into account makes detailed quantitative predictions for actual sites, which are illustrated by calculations for five diverse examples: Mariana, 16°N; Mexico, 17°N; Lesser Antilles, 13°N (Barbados); Alaska, 153°W (Kodiak); and Japan, 40°N. It requires as input the geometry of the overriding block and the top of the descending plate, the distribution of density and permeability of the overriding block, the speed of subduction, the density and rheological properties of the subducted sediment, and the rate of sediment input. Its predictions include the profile of thickness of the layer of subducted sediment (all sites; maximum of 360 m at Mariana, 5300 m at Japan), the velocities of flow in the layer (all sites), the shear stresses exerted on the walls (all sites; low beneath accretionary prisms, up to 6 MPa beneath Japan), the rate of offscraping (none at Mariana and late Tertiary Mexico; 85% of input at Lesser Antilles; includes melange at Japan), the distribution and rates of underplating (none at Mariana, extensive at Japan), the zones of possible subduction erosion (extensive at Mariana; local at the others), the amount of sediment subducted to the volcanic arc (all sites; 2% of input at Lesser Antilles, 100% at Mariana), the qualitative pattern of flow at the inlet (five basic patterns; all sites), the upward flow of melange in many instances (none at Mariana; extensive at Japan), and, under relatively rare conditions, the formation of large-scale melange diapirs (only at Lesser Antilles beneath Barbados Island).