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Calibrating the yield strength of Archean lithosphere based on the volume of TTG crust
Frontiers in Earth Science ( IF 2.0 ) Pub Date : 2020-08-24 , DOI: 10.3389/feart.2020.548724
Prasanna M. Gunawardana , Gabriele Morra , Priyadarshi Chowdhury , Peter A. Cawood

Lithospheric yield stress is a key parameter in controlling tectonic processes. Using high resolution, 2D numerical modelling, we calculate the yield stress for a range of conditions appropriate to the early-to-mid Archean Earth, including hotter mantle potential temperatures and Moho temperatures. We then evaluate its effect on generating tonalite-trondhjemite-granodiorite (TTG) crust and benchmark the results against the preserved igneous rock record. Our results indicate that lithospheric yield stress values lower than the present-day values (i.e. ≤ 100 MPa) can generate TTG volumes similar to those preserved in the rock record. The models further highlight the dominance of lithospheric dripping in producing the Archean TTGs. Large volumes of TTG melts form within the thin, tail portions of the drips as these regions are more efficiently heated by the enclosing hotter mantle. In contrast, only limited melting occurs within the thickened parts of lithosphere as they are significantly weak and cannot sustain crustal thickening for long time periods, resulting in its removal via dripping. This study, therefore, reaffirms the dominance of non-plate tectonic mechanisms in producing TTGs under the conditions that operated on the hotter Archean Earth.



中文翻译:

基于TTG地壳体积校准太古代岩石圈屈服强度

岩石圈屈服应力是控制构造过程的关键参数。使用高分辨率的2D数值模型,我们计算了适合于早至中古宙斯地球的一系列条件下的屈服应力,包括更热的地幔势温度和Moho温度。然后,我们评估其对生成斜长石-长白云母-碎屑闪长岩(TTG)地壳的影响,并根据保存的火成岩记录对结果进行基准测试。我们的结果表明,岩石圈屈服应力值低于当今的值(即≤100 MPa)可以产生与岩石记录中保存的相似的TTG体积。这些模型进一步强调了在生产太古代TTG时岩石圈滴落的优势。薄壁中会形成大量的TTG熔体,水滴的尾部,因为这些区域被封闭的较热地幔更有效地加热了。相反,由于岩石圈的增厚部分非常脆弱并且在长时间内无法维持地壳增厚,因此在岩石圈的增厚部分中仅发生有限的融化,从而导致其通过滴落而被去除。因此,这项研究重申了在较热的太古宙地球上运行的条件下非板块构造机制在生产TTG中的主导地位。

更新日期:2020-09-24
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