Physical-chemical controls of continental magmatism evolution remain enigmatic. Of prime and controversial nature is the temporal transition from calc-alkaline magmas to alkali basalts, correlated with a switch in tectonic regime from extension to compression. We perform 1D thermo-kinematic modelling to analyze the evolution of the thermo-rheological structure of the lithosphere in such settings using the Northwestern Pannonian Basin as a test-bed. Given well-known evidence for major reduction of brittle deformation parameters due to melt-related softening, we use a relatively low internal angle of friction. We demonstrate that at the termination of extension, the presence of intra-crustal low-viscosity layers in the lithosphere provides optimal condition for emplacement and differentiation of intermediate crustal magmatic chambers along the pathway of deep-sourced basaltic melts. In contrast, subsequent lithosphere cooling after the end of extension combined with tectonic and magmatic thickening lead to a disappearance of the low-viscosity layers and formation of lithospheric-scale faults. The latter serve as conduits for rapid ascent of uncontaminated alkali basaltic melts from the mantle to the surface. These findings shed new light on the geodynamic controls of magmatism in extensional settings.

大陆岩浆作用演化的物理化学控制仍然是个谜。主要的和有争议的性质是从钙碱性岩浆到碱性玄武岩的时间过渡，这与构造形态从扩展到压缩的转换有关。我们使用一维Pannonian盆地作为试验台，进行一维热运动学模型分析岩石圈热流变结构的演化。鉴于众所周知的证据表明，由于与熔体有关的软化，脆性变形参数会大大降低，因此我们使用相对较小的内摩擦角。我们证明，在扩展终止时，岩石圈中地壳内低粘度层的存在为沿深源玄武岩熔体路径的中间地壳岩浆室的沉积和分化提供了最佳条件。相反，延伸结束后的随后岩石圈冷却，构造和岩浆增厚相结合，导致低粘度层消失并形成岩石圈尺度断层。后者用作将未受污染的碱性玄武岩熔体从地幔快速提升到地表的管道。这些发现为伸展环境中岩浆作用的地球动力学控制提供了新的思路。延伸结束后，随后的岩石圈冷却，再加上构造和岩浆增厚，导致低粘度层消失并形成岩石圈规模的断层。后者用作将未受污染的碱性玄武岩熔体从地幔快速提升到地表的管道。这些发现为伸展环境中岩浆作用的地球动力学控制提供了新的思路。延伸结束后，随后的岩石圈冷却，再加上构造和岩浆增厚，导致低粘度层消失并形成岩石圈规模的断层。后者用作将未受污染的碱性玄武岩熔体从地幔迅速提升到地面的管道。这些发现为伸展环境中岩浆作用的地球动力学控制提供了新的思路。