Measurement on Wave Velocities of Rock Glasses to 900°C at 1.0 GPa and Geophysical Implications

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• 作者：Xi JIANG ; Hongsen XIE ; Wenge ZHOU ; Congqiang LIU ; Yonggang LIU ; Dawei FAN ; Fang WAN
• 关键词：high temperature and high pressure ; glass ; wave velocity ; low velocity layer
• 刊名：Earth Science Frontiers
• 出版年：2007
• 出版时间：May 2007
• 年：2007
• 卷：14
• 期：3
• 页码：158-164
• 全文大小：282 K

文摘

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