一种测定岩浆岩形成时岩浆流体上升速度的方法

摘要

静态流体中的球形固体重物的沉降速度服从Stocks公式，岩浆岩是由岩浆上升冷凝而成，在形成时与其中的深源包体也是这种关系，只是包体没有沉下去，反而随岩浆上升，说明岩浆上升速度大于最重最大包体的下沉速度，据此可确定该岩浆岩形成时岩浆流体上升的最小速度并推导出计算公式。以姑婆山花岗岩体主体为实例，用岩石成份、包体大小及其密度值、地质温度计和压力计算出的各种参数，求出了其岩浆上升的最小速度vmin。vmin值精度的影响因素有包体的深源性、已暴露出来的包体最大尺寸的确定、粘度的精度、固态岩石在熔融后体积的变化率公式的计算精确性等。%The sinking rate of the spherical heavy solid in static liquid is in accord with Stocks formula.The plutonic inclusions in igneous rocks which formed as a result of solidification of magma have the same relation as magma.However, without sinking away,these inclusions have risen up along with the magma,which shows that the rising rate of magma is higher than that of the heaviest and largest inclusion, there by, a method of the determination of the least rising rate of magma forming magmatite has been given.The formula of the method has been deduced and applied to the host body of Guboshan granite and vmin,the least rising rate of the magma forming granite has been is got with the parameters such as the size of inclusions,the density of the rock and the inclusions,the composition and temperature and pressure and water content of the forming rock.The decisive influence of precision of vmin comes from the confirmation of the plutonic and the largest size of the inclusions and the precision of viscosity of magma and the formula calculating the difference of volume between the rock and the magma forming the rock.