哀牢山变质带元江──墨江剖面岩石的纵波波速特征及其地质意义

依据研究区的地热梯度（25℃／km），在高温高压（最高温度为1050℃，最高压力为1.2GPa）条件下系统测量了横穿红河-哀牢山断裂带的元江-墨江地质剖面上的哀牢山岩群各类变质岩（千枚岩、片岩、浅粒岩、变粒岩、大理岩和片麻岩）的纵波速度．实验结果表明，不同岩类的纵波速度随温度压力变化的趋势不同．在相当于衷牢山岩群变质岩峰期变质温度和压力条件下（P=0．4-0.8GPa，T=35-700℃），测得大部分岩石的纵波速度为5．50－5．80km／s，这一纵波速度值与区域地球物理测深揭示的中地壳低速层的纵波速度相当因此，结合该区变质岩、地壳内热状态及地球物理测深研究成果可初步认为：组成哀牢山岩群的浅粒岩、变粒岩、酸性片麻岩以及部分千枚岩、片岩为该地区中地壳低速层的主要岩石类型．

COMPRESSIONAL WAVE VELOCITY IN THE METAMORPHIC ROCK OF YUANJIANG-MOJIANG PROFILE ACROSS AILAOSHAN METAMORPHIC BELT AND ITS GEOLOGY IMPLICATION

Compressional wave velocities for various metamorphic rocks （including phyllite, schist,granulitite, leucogranulitite, marble and gneiss） which belong to Ailaoshan group are measured at high temperature （up to 1050℃） and high pressure （up to 1. 2 GPa） conditions.According to the geothermal gradient （25） /km) of the study area, the temperature and pressure are increased simultaneously in every running. The experiment result indicates that the variations of compressional wave velocities in different rock types with increasing temperature and pressure are quite different. At the temperature and pressure of the peak metamorphism, the compressional wave velocities in most metamorphic rocks of Ailaoshan group are 5. 50-5. 80km/s. The compressional wave velocities are compatible with those of the low velocity layer occurring in the coddle crust of this area. By combined the experiment data, the seismic velocity models, and the metamorphic Petrology evidence, rock types of the low velocity layer in the coddle crust are constrained. It is possible that the leucogranulitite, granulitite, acidic gneiss and some of the phyllite and schist of the Ailaeshan group are the major rocks of the low velocity layer in the griddle crust.