浮力驱动的掘出变形:来自中国东部苏鲁造山带的证据

GSA Bulletin Pub Date : 2022-12-12 DOI:10.1130/b36532.1
Hao Yin, Guang Zhu, Xiaodong Wu, Nan Su, Yuanchao Lu, Shuai Zhang
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引用次数: 1

摘要

碰撞造山带中出土地壳的变形是由浮力还是构造应力驱动的仍不确定。中国东部苏鲁造山带包含缓慢俯冲和发掘的高压(HP) -超高压(UHP)地块,这为了解发掘变形是否由浮力驱动提供了很好的机会。我们使用野外和显微观察以及石英c轴织物来确定挖掘出的地壳切片的变形运动学,温度和演化。采用锆石U-Pb激光烧蚀-电感耦合等离子体-质谱法测定了变形和未变形岩脉的年代,以限制变形时间。我们的数据表明,在晚三叠世的挖掘过程中,每个地壳切片都参与了从上到北西(腹地)或从上到东南(前陆)的普遍韧性变形,并且每个切片的基底都记录了在随后的下伏切片挖掘过程中叠加的变形。南苏鲁造山带地壳发掘符合多期韧性挤压模式。各地壳片内的掘出变形运动学符合向上的不对称流动。高温剪切速率和剪切意义受高温剪切速率的影响,而高温剪切速率和剪切速率对高温剪切速率和剪切速率的影响较大。南苏鲁造山带的实例表明,地壳在掘出过程中的流动变形受浮力驱动,受黏性控制。与构造驱动变形的一致运动学不同,浮力驱动变形的运动学以单个地壳切片内剪切意义的变化为特征,因此可以用来区分两种类型的变形。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Buoyancy-driven exhumation deformation: Evidence from the Sulu orogen, eastern China
Whether deformation of exhumed crust in a collisional orogen is driven by buoyancy or tectonic stress remains uncertain. The Sulu orogen in eastern China contains slowly subducted and exhumed high-pressure (HP)−ultrahigh-pressure (UHP) terranes, which provide a good opportunity to understand whether the exhumation deformation was driven by buoyancy. We used field and microscopic observations as well as quartz c-axis fabrics to determine the deformation kinematics, temperatures, and evolution of the exhumed crustal slices. Deformed and undeformed dikes were dated by using the zircon U-Pb laser ablation−inductively coupled plasma−mass spectrometry method to constrain the timing of deformation. Our data demonstrate that each crustal slice was involved in pervasive top-to-the-NW (hinterland) or top-to-the-SE (foreland) ductile deformation during Late Triassic exhumation, and that the base of each slice records deformation that was superimposed during the subsequent exhumation of the underlying slice. The crustal exhumation of the southern Sulu orogen is consistent with the multistage ductile extrusion model. The kinematics of exhumation deformation within each crustal slice conform to an upward asymmetric flow. The flow velocity and corresponding shear sense were affected by temperature variations in each HP slice, whereas they were sensitive to migmatization within the UHP slices. The southern Sulu orogen examples show that crustal flow deformation during exhumation was driven by buoyancy and controlled by viscosity. Unlike the consistent kinematics of tectonics-driven deformation, the kinematics of buoyancy-driven deformation are characterized by variations in the senses of shear within a single crustal slice, and this can therefore be used to distinguish the two types of deformation.
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