Image based modelling of lateral magma flow: the Basement Sill, Antarctica

The McMurdo Dry Valleys magmatic system, Antarctica, provides a world-class example of pervasive lateral magma flow on a continental scale. The lowermost intrusion (Basement Sill) offers detailed sections through the now frozen particle microstructure of a congested magma slurry. We simulated the flow regime in two and three dimensions using numerical models built on a finite-element mesh derived from field data. The model captures the flow behaviour of the Basement Sill magma over a viscosity range of 1–104 Pa s where the higher end (greater than or equal to 102 Pa s) corresponds to a magmatic slurry with crystal fractions varying between 30 and 70%. A novel feature of the model is the discovery of transient, low viscosity (less than or equal to 50 Pa s) high Reynolds number eddies formed along undulating contacts at the floor and roof of the intrusion. Numerical tracing of particle orbits implies crystals trapped in eddies segregate according to their mass density. Recovered shear str...

南极麦克默多干谷岩浆系统是大陆尺度广泛发育侧向岩浆流动的世界级研究范例。其最底部侵入体——基底岩床（Basement Sill）保留了现今已冻结的拥堵岩浆浆体的颗粒微观结构详细剖面。本研究基于野外实测数据导出的有限元网格构建数值模型，对该体系的二维与三维流态开展了模拟。该模型可复现基底岩床岩浆在1~10^4 Pa·s黏度范围内的流动行为，其中黏度上限（≥10^2 Pa·s）对应晶体体积分数介于30%~70%的拥堵岩浆浆体。本模型的一项创新性发现为：在侵入体底板与顶板的起伏接触面上，形成了瞬态、低黏度（≤50 Pa·s）的高雷诺数（Reynolds number）涡旋。对颗粒运动轨道的数值示踪结果表明，被困于涡旋中的晶体将依据其质量密度发生分异。本次研究获得的剪切……