【摘要】 利用超声波反射法,在1.0GPa、最高温度分别达900℃和730℃条件下,测量了岩石成分从酸性到基性的7种熔融玻璃的纵波波速(vp)和横波波速(vs)随温度的变化。实验过程证明,高压下升温过程中样品被压缩导致了样品中弹性波走时减少,而降温过程中样品长度基本保持不变。结果显示,1.0GPa下,随实验温度升高,不同成分玻璃的vp首先以-0.2×10-3km.s-1.℃-1到-0.7×10-3km.s-1.℃-1不等的速率缓慢降低,而其vs多以-0.1×10-3km.s-1.℃-1速率随温度升高而降低。当温度高于玻璃转变温度(Tg)后,玻璃的vp开始以-0.8×10-3km.s-1.℃-1到-3.6×10-3km.s-1.℃-1不等的速率快速下降。根据玻璃vp随温度变化速率的改变,拟合出这几种玻璃的转变温度从584℃到654℃。由实验获得的玻璃波速,利用Voigt-Reuss-Hill(VRH)平均计算出下地壳岩石中玻璃的存在将降低岩石的波速,并由此为下地壳低速层提出一种新的解释,即非晶质体的存在可能在下地壳形成地震波低速层。更多还原

【Abstract】 At 1.0GPa, compressional and shear wave velocities (vp and vs) of seven types of glass are measured as functions of temperature up to 900 ℃ and 730 ℃, respectively. Experimental runs indicated that, with elevating temperature under high pressure, the compression of glass is responsible for the decrease of travel time in the sample and the glasses show little change in height during cooling process. When the temperatures are lower than the glass transition temperatures (Tg), it is found that the temperature derivatives of velocities of the glasses are between -0.2×10-3 km·s-1·℃-1 and -0.7×10-3 km·s-1·℃-1 for vp and almost -0.1×10-3 km·s-1·℃-1 for vs, respectively. At higher temperature (T>Tg), vp of the glasses decrease quickly with temperature derivatives between -0.8×10-3 km·s-1·℃-1 and -3.6×10-3 km·s-1·℃-1. According to the change in temperature derivatives of vp, the glass transition temperatures are determined to be between 584 ℃ and 654 ℃. Using the Voigt-Reuss-Hill(VRH)average method, it is calculated that the wave velocities of the lower crustal rocks decrease with increase in glass content. Because of this, we suggest that the low velocity layer in lower crust is a function of the glass contents in rocks, which results in the decrease in the wave velocity of rocks in lower crust.更多还原