岩浆物理过程对钾质煌斑岩岩相特征的控制机制

THE CONTROL OF PHYSICAL PROCESSES OF MAGMA ON THE CHARACTERISTICS OF PETROGRAPHY OF POTASSIC-LAMPROPHYRE

The O1-Cpx-lamprophre and Le-O1-Cpx-lamprophre form the westrn border of Yangtze platform are very similar in composition bue quite different in petrography.The main discrepancy is that,the former contains peridotite xenoliths,with stable phlologopites both ,in porphyritic crystals and matrix and sanidines in the later has no xenoliths ,with unstable black phlologopites as porphyritic crystals but stable oncs and leucites in the matrix .The results of analyses and calculations of physical properties of the two types of rocks show that the main factors causing the differents in petrography between them are as follow:the densities of two magmas are quite difrerent.This will causedifferent ascent velocities and then different diffusion rates of volatile in magma. The change of the pH2o in magmas during their ascenting triggers the changes of the stability of phlologopite,leucite and sanidine.