斜长石环带的成因机制

GENETIC MECHANISM OF PLAGIOCLASE ZONING

系统地分析了外长石环带的研究现状，并提出了外长石的小尺度韵律环带起因于自组织过程，而与环境因素无关，其形成对应着相对静态的环境；斜长石的大尺度韵律环带刚起因于环境（主要是温度、压力）的“周期性”波动，而不可能是自组织成因，其形成过程记录了环带生长期间岩浆活动的情况（岩浆的温度、压力、组分浓度等）。斜长石的小尺度韵律环带是在结晶五度稳定在国相线附近的温度范围内形成的。当结晶温度低于团相线温度时，则形成非韵律环带或枝晶甚至玻璃体；非韵律型环带是由于环境的温度或压力的持续变化而形成的，它的结晶温度比大环带中套小环带形成时的结晶温度要低一些，或者说其非平衡程度更大一些。

This paper systematically ana1yses the current situation of research on plagioclase zoning and points and that the middle- and small-scale oscillatory zoning in plagioclase is formed organization. It has nothing to do with environmental factors. The large-scale oscillatory zoning in plagioclase is formed as a result of the 'periodic' vibration of environment (temperature, pressure), but not of self-organization. Its formation has recorded the magmatic activities (temperature, pressure and concentration of magma). The small-scale oscillatory zoning in plagioclase is formed at the crystal-growth temperature near the solidus. When the crystallization temperature is blow the solidus, non-oscillatory zoning or dendritic crystal and glass mass will be formed. The nonoscillatory zoning in plagioclase is formed as a result of persisting variations in temperature or pressure of the environment. Its crystallization temperature is lower than that of the small-scale zoning within the large-scale zoning, or its nonequilibrium is greater.