Modern-style continental tectonics since the early Archean
Modern-style continental tectonics since the early Archean
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DOI：
10.1016/j.precamres.2024.107324
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发表时间：
2024-04
影响因子：
3.8
通讯作者：
Alex Copley;Owen Weller
中科院分区：
文献类型：
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作者：
Alex Copley;Owen Weller
我们通过将我们对控制大陆当前行为的原理的理解与前寒武纪岩石记录中的现有观测结果相结合，推断出前寒武纪大陆构造的性质，而地球表面的大部分地区并不类似于板块构造。我们表明，较热的地幔潜在温度对大陆流变性和行为影响不大。相比之下，较高的放射加热速率在地壳融化和随后的大陆流变演化中发挥了关键作用，尽管加热、融化和脱水之间的反馈会导致前寒武纪大陆流变和变形速率与现在相似。至少到太古代早期，甚至可能更早，大片地壳中保存的变形结构和变质岩的压力-温度历史表明，造山活动是通过坚硬的逆冲前陆上方的剪切和逆冲堆积而形成的。这种造山方式需要存在刚性的地壳块，它们是地壳和岩石圈地幔增厚后先前熔体提取的无水残留物。山脉前陆的流变学控制着可支持的地壳厚度对比，并且地壳厚度与辐射加热速率一起控制着所达到的温度。地球历史上放射性加热的减少与能够支撑厚山脉的坚固地壳块体的发展之间的相互作用，导致了在太古宙热大陆造山事件期间形成英闪长岩-长斜长岩-花岗闪长岩（TTG）熔体的最佳条件，解释了它们的太古宙盛行和随后的衰落。然而，至少自太古宙早期以来，大陆构造的整体风格一直保持不变，而 TTG 岩石成因只是代表了这种构造风格叠加在更高的放射成因加热速率上。我们认为，这种本质上现代风格的大陆变形之前是一个（早期？）冥宙构造阶段，类似于蛋奶冻上皮肤的变形。含水断层带太弱，无法在类地行星上形成“停滞盖”，并且密度驱动的垂直运动（例如“弧垂”）以微不足道的速度发生，进一步强调了从太古代早期开始大陆构造的均变性本质。
We infer the nature of continental tectonics in the Precambrian by combining our understanding of the principles that govern the present-day behaviour of the continents, which over large parts of the Earth’s surface does not resemble plate tectonics, with the available observations from the Precambrian rock record. We show that the hotter mantle potential temperature had little effect on continental rheology and behaviour. In contrast, higher rates of radiogenic heating played a key role in crustal melting and the subsequent rheological evolution of the continents, although feedbacks between heating, melting and dehydration would have resulted in Precambrian continental rheology and deformation rates similar to the present day. By at least the early Archean, and possibly earlier, deformation fabrics preserved in large swathes of crust and the pressure- temperature histories of metamorphic rocks imply mountain-building by shearing and thrust-stacking above rigid underthrusting foreland. This style of mountain-building requires the presence of rigid crustal blocks, which are the anhydrous residue of prior melt extraction following thickening of the crust and lithospheric mantle. The rheology of the forelands of mountain belts controls the crustal thickness contrasts that can be supported, and along with the rate of radiogenic heating that crustal thickness controls the temperatures attained. The interplay between decreasing radiogenic heating over Earth history and the development of strong crustal blocks that can support thick mountain ranges leads to optimal conditions for the generation of tonalite–trondhjemite–granodiorite (TTG) melts during hot Archean continental mountain building events, explaining both their Archean prevalence and subsequent decline. However, the overall style of continental tectonics has remained unchanged since at least the early Archean, and TTG petrogenesis simply represents this style of tectonics superimposed upon a higher rate of radiogenic heating. We suggest that this intrinsically modern-style deformation of the continents was preceded by a phase of (early?) Hadean tectonics resembling the deformation of skin on custard. Hydrous fault zones are too weak to form a ‘stagnant lid’ on Earth-like planets, and density-driven vertical motions (e.g. ‘sagduction’) occur at insignificant rates, further emphasising the uniformitarian nature of continental tectonics from the early Archean onwards.