安第斯山脉的加宽：俯冲动力学和地壳楔构造之间的相互作用
Widening of the Andes: an interplay between subduction dynamics and crustal wedge tectonics
摘要：
大陆岩石圈的缩短通常是由地幔岩石圈中巨型逆冲断层之上地壳楔体的增长所适应的。我们发现，在南美洲西部边缘的缩短轨迹在很大程度上是由板的几何形状控制。数值模型证实，水平俯冲有利于压缩远离海沟，以上的软流圈楔和俯冲板陡倾段。结果，第二个地壳楔在大陆腹地生长，并扩大了安第斯山脉。在玻利维亚的造山带中，这个楔对应于东科迪勒拉山脉，其增长是由水平俯冲的主要事件引发的。当板片返回到一个更陡的倾角，缩短和隆起的追求，促进了大陆岩石圈的结构和热化学蚀变。我们回顾了南美洲不同纬度下发生的连续水平俯冲事件，并表明它们解释了安第斯山脉的历时性扩大。我们推断，现今的安第斯山脉的分段地形的结果从纬度可变的，瞬态板动力学和上板块构造之间的相互作用在新生代。我们要强调的是，板块变平或不变平是决定安第斯山脉在任何纬度上的宽度的主要驱动机制。
英文摘要：
Shortening of the continental lithosphere is generally accommodated by the growth of crustal wedges building above megathrusts in the mantle lithosphere. We show that the locus of shortening in the western margin of South America has largely been controlled by the geometry of the slab. Numerical models confirm that horizontal subduction favors compression far from the trench, above the asthenospheric wedge and steeply dipping segment of the subducting slab. As a result, a second crustal wedge grows in the hinterland of the continent, and widens the Andes. In the Bolivian orocline, this wedge corresponds to the Eastern Cordillera, whose growth was triggered by a major episode of horizontal subduction. When the slab returned to a steeper dip angle, shortening and uplift pursued, facilitated by the structural and thermo-chemical alteration of the continental lithosphere. We review the successive episodes of horizontal subduction that have occurred beneath South America at different latitudes and show that they explain the diachronic widening of the Andes. We infer that the present-day segmented physiography of the Andes results from the latitudinally variable, transient interplay between slab dynamics and upper plate tectonics over the Cenozoic. We emphasize that slab flattening, or absence thereof, is a major driving mechanism that sets the width of the Andes, at any latitude.
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