华北地台太行-五台和阴山地块地壳物质组成——岩石地震波速实验证据

CONSTITUTION OF CRUSTAL MATERIALS IN TAIHANG_WUTAI AND YINSHAN TERRAINS, NORTH CHINA CRATON: EVIDENCE FROM SEISMIC VELOCITY IN ROCKS

在模拟地壳的温度和压力条件下，测定了华北地台太行－五台和阴山地块的主要变质岩群和侵入岩共５４个岩石样品的纵波速度（ｖｐ）．各类岩石的ｖｐ在约４～１０ｋｍ深度内上升很快，在１０～２５ｋｍ内继续增大，但是幅度变小，在该深度范围内达到了ｖｐ最大值；在３０～３５ｋｍ之后到５０ｋｍ深度内的ｖｐ都趋于恒定．综合对比地壳的波速结构和岩石的波速特征表明，在太行－五台地块，五台群、滹沱群和古老花岗岩岩类构成上地壳，阜平群和恒山群构成中地壳，集宁群代表了下地壳的岩石组成；在阴山地块，马家店群、二道凹群、色尔腾山群和古老侵入岩类是中地壳和上地壳的组成部分。

P_wave velocities ( v p) in 54 rock samples collected from the major metamorphic rock series and intrusive rocks in the Taihang_Wutai and Yinshan terrains of North China craton were measured at the simulated crustal temperature and pressure. v p in the samples increase rapidly in the depth of 4-10km, then continue to increase at a slower speed to the maximum v p in the depth of 10-25km and then remain nearly constant in the depth of 30-50km. A comprehensive correlation between the P_wave velocity structure of the regional crust and those of the samples suggests the following conclusions. (1) In the Taihang_Wutai terrain, the Wutai Group, Hutuo Group and palaeo_granitoids constitute the upper crust, the Fuping and Hengshan groups constitute the middle crust, and the Jining Group constitutes the most suitable candidate for the lower crust. (2) In the Yinshan terrain, the upper and middle crusts are mainly composed of the Majiadian Group, the Erdao'ao Group, the Se'ertengshan Group and palaeo_granitoids, with the rocks in the Wulashan Group as the representative of the lower crust.