华北太古宙长英质岩石的地震波速度及其在地壳中的位置

SEISMIC WAVE VELOCITY OF ARCHEOZOIC FELSIC ROCKS FROM NORTH CHINA AND ITS EXISTING LOCATION IN THE CRUST

研究了两项内容 :1在室温高压和高温高压条件下 ,华北地区长英质结晶岩的压缩波速度 ;2在常压和石英 α- β相变温度下 ,长英质岩石的加热声发射 .结果表明 :在相同的温压条件下 ,长英质结晶岩的波速明显低于基性岩 ,而与变质相的关系不大 ;含石英岩石的波速曲线具有与其它任何岩石不同的曲线形态 ,显示了 α- β相反应峰 ;在常压下加热岩石至石英相变点时 ,长英质深变质岩和岩浆花岗岩产生声发射 ,另一种交代成因的花岗岩不产生声发射 .其地质意义表明 :结合其它地学资料解释了华北克拉通区的地壳组成 ,阐明了 α石英和β石英的存在空间 ;说明了新生代构造沉降区下地壳岩石中石英的α-β相变以及角闪石和黑云母的脱水熔融是沉降区和隆起区间断裂活动 (张性断裂 )

WT5BZ]This paper contains two contents. The first is seismic velocity of felsic crystalline rocks of North China at room temperature and high pressures and at both high temperatures and pressures. The second is heating acoustic emission of felsic rocks at atmosphere pressure and the temperature of the quartz α β transition. The results of these experiments show that velocities of the felsic crystalline rocks are obviously lower than that of the basic rocks and no visible relationship with metamorphic phase. The velocity curves of rocks containing quartz display peaks of the α β phase reaction, which are different from other rocks in configuration. When the heating temperature is up to the phase transition temperature of quartz at the atmosphere pressure, felsic hypometamorphic rocks and magma granite produce acoustic emission. While the other kind of the granite generated by metasomatism does not produce acoustic emission. These results have the following implications. It explains the crustal constitution of the North China craton in combination with other geoscientific data, and clarifies the existing space of α quartz and β quartz. It also indicates that the α β quartz transition and dehydration melting of amphibole and biotite in the lower crustal rocks of the Cenozoic tectonic subsidence area are likely associated with faulting (tensional fault) and seismic activities.