榴辉岩的弹性波速评述  

ELASTIC WAVE VELOCITY IN ECLOGITE:A REVIEW

作　　者：赵志丹[1,2] 周文戈[1] 谢鸿森[1] 朱茂旭[1] 

机构地区：[1]中国科学院地球化学研究所 [2]中国地质大学地球科学与资源学院,北京100083

出　　处：《地学前缘》2000年第1期259-270,共12页Earth Science Frontiers

基　　金：国家自然科学基金资助项目!(496 72 142;4990 40 0 5 )

摘　　要：文中评述了榴辉岩的密度和高温高压下的纵波速度、速度各向异性、泊松比以及榴辉岩声软化现象的成因 ,着重介绍了榴辉岩的密度和波速对探讨岩石圈物质组成、莫霍界面性质、超高压岩石对实现壳幔物质交换的重要意义。榴辉岩的密度为 3 2～ 3 6 5g·cm-3 ,其中超高压榴辉岩具有更高的密度 (3 4～ 3 6 5g·cm-3 )。榴辉岩的纵波速度 (vp)在 1GPa时为 7 3～8 9km·s-1,其裂隙闭合压力可能高于 1GPa。榴辉岩的压力系数为 0 3～ 0 4km·s-1·GPa-1,温度系数为 - 3 4× 10 -4 km·s-1·℃ -1。它具有最弱的vP 各向异性 (<3% )。超高压榴辉岩的泊松比为 0 2 54～ 0 2 75。大别山榴辉岩的密度和波速研究表明 ,现今的大别山深部地壳可能依然存在榴辉岩 ,但数量应很少 ;大别山上地幔具有同超高压榴辉岩类似的弹性特征 ;拆沉作用是解释超高压榴辉岩折返机制的重要模式之一 ;榴辉岩的形成过程包含了壳幔物质循环作用 ,一部分榴辉岩已拆沉进入深部地幔 ,另一部分则快速折返至地壳内或通过其他构造作用进一步抬升、暴露地表。Elastic wave velocity in eclogites have been well studied recently Eclogite has experienced high pressure and ultrahigh pressure metamorphism formed in the mantle condition and came back to the crust The elastic parameters,excluding p and s wave velocity,velocity anisotropy and Poisson's ratios are very important for discussing the constitution and state of the lithospheres,nature of the Moho and the crust mantle recycling Eclogites have the highest density,ranging from 3 2 to 3 65g·cm -3 ,and the highest p wave velocity (7 3～8 9km·s -1 at 1 GPa) in all the metamorphic rocks Density and p wave velocity exhibit a linear relationship in eclogites The microcracks closure pressure in eclogites may be higher than 1GPa Pressure derivatives of eclogite range from 0 3 to 0 4 km·s -1 ·GPa -1 Average temperature derivatives of eclogite are around -3 4×10 -4 km·s -1 ·℃ -1 Eclogites have the lowest p wave velocity anisotropy (<3%) in all the rocks The elastic wave velocity and density of eclogites imply that eclogites may be still existing in the lower crust with an amount less than 50%,which is responsible for the deep crustal reflectors in Bergen Arcs of Norway,and crustal high speed zones in Dabie Orogenic Belt,Eastern China The upper mantle of the Dabieshan area is very similar to the ultrahigh pressure eclogites in elastic characteristics Much higher density of eclogites than that of the mantle rocks and the upper mantle suggest that the lower parts of the subducted lithosphere could break off and detach into the mantle The well accepted model of delamination is one of the most suitable candidates in explaining the origin of eclogite Crust mantle recycling is enclosed in the formation process of eclogites Some eclogites formed in the mantle could sink into and become one of the endmembers of the mantle,whereas other small amount of eclogites will come back to the crust and exposed in the surface by exhumation of metamorphic terranes

关 键 词：榴辉岩 弹性波速 密度 壳-幔循环 大别山 

分 类 号：P588.3[天文地球—岩石学]