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火山碎屑堆积物在矿物组分、成岩温度及结晶程度等方面的系统差异有力地证实了岩浆房中存在着化学不均一性。虽说人们普遍赞同这一看法,但有关其成因的假说,目前还没有一种能被广泛接受.在这类文献著作中,化学边界层流假说最引人注目,而其它有潜在价值的假说则常多未予以考虑.本文将对一些有代表性的假说进行研究和评述,并试图用定量的方法评价有关产生组分不均一性假说的潜力。我们的结论概述如下:根据成分分带喷发的火山资料,演化岩浆的生成速率为10~(-2)-10~(-4)km~3/a(a=年),通常为～10~(-3)3km~3/a.玄武质岩浆的侵入引起酸性围岩发生熔融作用,这一假说似乎是可行的,因为演化熔体的生成速率与火山观察结果是一致的.然而某些火山系统并未出现这一模式所预期的那种广泛的同位素混染.多孔介质流(在岩浆房的边缘液-晶糊状体中,它可将部分熔体从岩浆源区和边界层中分离出来)的机制是不可能的,因为多孔介质的渗透性很弱.有限扩散化学边界层可把大量富 H_2O 熔体搬运至岩浆顶部,但扩散较慢的组分(如 SiO_2)只有在与熔体中流动更快的组分扩散结合时,才被大量搬运带走。不过如果非对角扩散系数等于对角扩散系数值的10%或更大些时,则交叉耦合作用在岩浆分层中就会起到重要作用。
Systematic differences in volcanic debris accumulation in mineral composition, diagenetic temperature and degree of crystallinity strongly confirm the presence of chemical heterogeneity in the magma chamber. Although this view is generally accepted, no hypothesis about its cause has yet been widely accepted. In these literary works, the chemical boundary laminar flow hypothesis is the most notable, while other potentially valuable hypotheses Often not considered .This article will conduct research and review of some representative hypotheses, and try to use quantitative methods to evaluate the potential for generating heterogeneity of components. Our conclusion is summarized as follows: According to the volcanic data of the component zonation eruptions, the evolution magmatism rate is between 10 ~ (-2) -10 ~ (-4) km ~ 3 / a (a = year) (-3) 3km ~ 3 / a. The hypothesis that the intrusion of basaltic magma caused the melting of acidic wall rocks seems viable because the rate of evolution of the evolutionary melt is consistent with volcanism observations. However, some volcanoes The system does not exhibit the kind of widespread isotope contamination expected for this model Porous media flow (in the marginal liquid-crystal paste of the magma chamber it separates part of the melt from the magma source zone and the boundary layer Out) mechanism is not possible because of the weak permeability of porous media. The limited diffusion chemical boundary layer can transport a large amount of H_2O-rich melt to the top of the magma, but the slower diffusion components (such as SiO_2) Body flow faster components diffusion combination, was removed by a large number of transport. However, if the non-diagonal diffusion coefficient is equal to 10% or more of the value of the diagonal diffusion coefficient, the cross-coupling effect plays an important role in magma stratification.