The convective liquidus in a solidifying magma chamber: a fluid dynamic investigation
The convective liquidus in a solidifying magma chamber: a fluid dynamic investigation
复制标题
凝固岩浆室中的对流液相线：流体动力学研究
作者：
G. Brandeis;B. Marsh
岩浆房边缘的结晶引起强烈的粘度变化1，最近的研究2-4表明这种结晶如何影响对流的活力。在这里，我们报告了一种从上方冷却的石蜡层凝固的实验研究。当流体过热时，对流在冷却开始时开始，但强度迅速减弱。一旦这一层失去了过热，对流就停止了，进一步的冷却就是传导。然后，内部温度保持不变，直到上地壳遇到。我们将对流液相线定义为对流非常弱或不存在的温度阈值。在天然玄武岩系统中，对流液相线虽然严格地说是未知的，但可能非常接近真正的液相线。因此，在许多岩浆室的结晶过程中，快速对流可能不是主要过程；相反，对流是相平衡、晶体生长和热传递之间总体密切平衡的一部分。
CRYSTALLIZATION at the margins of magma chambers induces strong viscosity variations1, and recent studies2–4 have shown how such crystallization affects the vigour of convection. Here we report an experimental study of the solidification of a layer of paraffin cooled from above. When the fluid is superheated, convection sets in at the beginning of cooling but rapidly decreases in intensity. Once the layer has lost its superheat, convection ceases and further cooling is by conduction. The interior temperature then remains constant until encountered by the upper crust. We define the convective liquidus as the temperature threshold below which convection is very weak or non-existent. In natural basaltic systems, the convective liquidus, although strictly unknown, may be very close to the true liquidus. Rapid convection may therefore not be a dominant process during the crystallization of many magma chambers; instead, convection is part of an overall intimate balance between phase equilibria, crystal growth and heat transfer.