席状岩浆房中的岩浆冷却及动力稳定性

关于岩浆房中岩浆的结晶分异方式一直存在着争议，其基本矛盾在于对岩浆冷却历史及热不稳定性可能引起的对流形式的理解各不相同。本文在充分考虑席状岩浆房的基本物理特征的基础上，建立了稳定岩浆体系的动态冷却模型，并以攀枝花层状岩体为例，计算了相应的温度场、密度场及粘度场。同时，提出了一种基于能量守恒的、对热不稳定性进行分析的新方法。计算了热不稳定性可能引起的对流强度、对流区域及对流时间，并深入讨论了在一定的热不稳定状态下，不同的岩浆屈服强度对对流特征参量的影响。结果表明，在该岩体的整个固化过程中，如果曾发生过自发对流，其对流也是极微弱而短暂的，不会影响中下部岩浆房中岩浆的固化和结晶。这一结论与对该岩体的实际观察相符。

The Cooling and Dynamic Stability of Magma in Sheetlike Magma Chamber

The modes of the fractional crystallization in magma chamber were discussed for many years. The main reason is that there are several different views on the cooling and convection patterns caused by the heat instability of magma system. Considering the fundamental physical ptoperties of sheetlike magma chamber, a dynamic pattern of magma cooling is established in this paper. Based on the laws of transformation and conservation of energy, we put forward a new analysis method for the heat instability of magma system. Panzhihua layered intrusion is taken as an example, the calculations of temperature field, density field and viscosity field, strength, region and duration of convection are Perpormed and the influence of the yield strength on the characteristic parameters of convection is discussed. The calculations indicates that the convection was very weak and transient and could not affect the middle and lower region of the magma chamber, if convection could ever occur spontaneously. This conclusion is consistent with the actual observation.