Rapid emplacement of a mafic dyke or sill at mid-crustal depth heats and possibly melts the felsic wall rock followed by solidification. Associated volume changes generate stresses, possibly enforcing brittle failure and melt migration. We model the evolution of melting, solidification, temperature, and stress including visco-elastic relaxation in 1D - dykes or -sills using realistic rock rheologies of the Weschnitz pluton (Odenwald). For deep emplacement (Case 1, 15.3 km) extensive contact melting of the wall rock occurs, for shallow emplacement (Case 2, 10 km) it is negligible. The stresses are zero at high melt fractions, but increase during solidification and cooling: The intrusion orthogonal stress is always zero. The intrusion parallel stress within the intrusion is tensile (O(200 MPa)). It relaxes on a time scale between a few years (Case 1) and 0.6 m.y. (Case 2). Within the wall rock is compressive during heating, but becomes tensile under solidification and cooling. Wall rock stresses relax on a time scale of months to 100 years. A Deborah number is defined based on viscous to thermal relaxation allowing generalization of our results. Adding lithostatic stresses, the total stresses of Case 1 remain below the brittle strength, while for Case 2 they may exceed it. Adding the lithostatic pressure to the melt pressure, the effective stresses exceed the brittle strength and intrusion orthogonal tensile fractures are predicted. Combined with the pressure gradient within the over-pressurized felsic melts generated in the wall rock, this explains the migration of felsic contact melt into shrinkage cracks of the mafic sill in the Weschnitz pluton.

中文翻译：

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窗台和堤坝的深埋与浅埋：热粘弹性模型的新见解


镁铁质岩脉或基岩在中地壳深度的快速就位会加热并可能熔化长英质围岩，然后凝固。相关的体积变化会产生应力，可能导致脆性破坏和熔体迁移。我们使用韦施尼茨岩体 (Odenwald) 的真实岩石流变学来模拟一维堤坝或基台中的熔化、凝固、温度和应力的演化，包括粘弹性松弛。对于深侵位（案例 1，15.3 公里），围岩发生广泛的接触熔化，对于浅侵位（案例 2，10 公里），可以忽略不计。在高熔体分数下应力为零，但在凝固和冷却过程中应力增加：侵入正交应力始终为零。侵入内的侵入平行应力为拉伸 (O(200 MPa))。它在几年（案例 1）和 0.6 m.y 之间的时间尺度上松弛。 （案例2）。围岩内部在加热过程中受到压缩，但在凝固和冷却过程中变成拉伸状态。围岩应力在数月至 100 年的时间范围内松弛。黛博拉数是根据粘性到热弛豫来定义的，从而可以推广我们的结果。添加岩石静应力后，情况 1 的总应力仍低于脆性强度，而情况 2 的总应力可能超过脆性强度。将岩石静压力添加到熔体压力中，有效应力超过脆性强度，并且预测侵入正交拉伸断裂。结合围岩中产生的超压长英质熔体内的压力梯度，这解释了长英质接触熔体迁移到韦施尼茨岩体中镁铁质基台的收缩裂缝中。