Oblique contractional reactivation of inherited heterogeneities: Cause for arcuate orogens
Oblique contractional reactivation of inherited heterogeneities: Cause for arcuate orogens
复制标题
遗传异质性的倾斜收缩重新激活：弓形造山带的原因
作者：
E. Calignano;D. Sokoutis;D. Sokoutis;E. Willingshofer;Jean;F. Gueydan;F. Gueydan;S. Cloetingh
我们使用岩石圈尺度的模拟模型来研究斜向缩短作用下先前存在的不均匀性的重新激活及其与弧形造山带起源的关系。继承的流变非均匀性的重新激活是造山过程中挤压环境中变形局部化和随后收缩构造形成的重要机制。然而，一旦大陆岩石圈缩短，岩石圈中继承的不均匀性的存在本身并不足以使其重新激活。异质性取向在确定是否发生再活化以及在何种程度上发生再活化方面很重要。本研究旨在通过模拟实验揭示这一过程，其中线性岩石圈非均匀性与缩短方向呈不同角度的趋势。特别地，研究的关键参数是强畴（SD）相对于缩短方向的取向（角度α）。实验结果表明，当α ≥ 75°（高韧性）时，可沿整个SD沿着再活化，并形成线性造山带。对于α ≤ 60°（低结晶度），模型的特征是弧形造山带的发展，SD保持部分非再活化。这些结果为某些弧形造山带的起源提供了一种新的机制，其中造山带的形成不是由压痕或俯冲过程驱动的，而是由继承的不均匀性的斜向缩短驱动的，例如美国南部的Ouachita造山带。
We use lithospheric‐scale analog models to study the reactivation of pre‐existing heterogeneities under oblique shortening and its relation to the origin of arcuate orogens. Reactivation of inherited rheological heterogeneities is an important mechanism for localization of deformation in compressional settings and consequent initiation of contractional structures during orogenesis. However, the presence of an inherited heterogeneity in the lithosphere is in itself not sufficient for its reactivation once the continental lithosphere is shortened. The heterogeneity orientation is important in determining if reactivation occurs and to which extent. This study aims at giving insights on this process by means of analog experiments in which a linear lithospheric heterogeneity trends with various angles to the shortening direction. In particular, the key parameter investigated is the orientation (angle α) of a strong domain (SD) with respect to the shortening direction. Experimental results show that angles α ≥ 75° (high obliquity) allow for reactivation along the entire SD and the development of a linear orogen. For α ≤ 60° (low obliquity) the models are characterized by the development of an arcuate orogen, with the SD remaining partially non‐reactivated. These results provide a new mechanism for the origin of some arcuate orogens, in which orocline formation was not driven by indentation or subduction processes, but by oblique shortening of inherited heterogeneities, as exemplified by the Ouachita orogen of the southern U.S.