摘要
火成岩石学研究中,通常仅根据岩套的化学变异来推断是否发生过结晶分异作用,而且认为结晶分异的主要机理是晶体在牛顿流体中的重力分离。然而,在大多数情况下,岩浆是一种非牛顿流体。本文导出的晶体沉降速率的表达式说明,晶体能否重力分离,不仅与晶体和流体相间的密度差及晶体大小有关,还与岩浆粘度、屈服强度有关,而岩浆的流变学性质又受岩浆成分、晶体含量和物化条件等的控制。因而,深度、地温、构造环境和岩浆上升速度等对结晶分异作用都有影响。文中导出的宾汉体岩浆中包体沉降速度的表达式,普遍适用于含深源包体的岩浆的最小上升速度的计算。本文还评述了结晶分异作用微量元素模型在应用上的动力学限制条件。
In the study of igneous petrology, the crystallization differentiation is usually proposed, only based on the chemical variation of rock suite, and its primary mechanism is regarded as gravitational segregation of crystals in the Newtonian fluid. However, magma is a non-Newtonian fluid in most instances. The degree of gravitational segregation depends on viscosity(η)and yield strength(σ0) of magma, as well as density difference ( △p ) between the crystal and melt, and crystal size.
where g, a and r represent the acceleration of gravity, settling rate and radius of crystal in a Bingham plastic magma, respectively. The Theological properties of magma are controlled by magma composition, crystal content, physical and chemical conditions and others. Thus, depth, geotherm, tectonic setting and ascent rate of magma also exert some influence on crystallization differentiation. The nodule settling velocity ( the minimum ascent velocity of magma ) a, is given by
where R and △ρ denote the radius of nodule and density difference between the nodule ( ρs ) and magma (ρf), respectively, Re is the particle Renolds number. In addition, a review is made of some basic kinetic constraints on the application of trace element models to crystallization differentiation in the present paper.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
1989年第3期245-252,共8页
Earth Science-Journal of China University of Geosciences
关键词
结晶
分异作用
岩浆动力学
magma-dynamics, crystallization differentiation, settling rate of crystal and nodule, Bingham plastic magma, diffusion
