高压、超高压变质岩形成深度讨论

根据硅酸盐矿物压缩系数的实测值与一些地质现象结合，提出岩石圈中壳幔边界处可能存在负荷压力与来自地幔的压力结合而形成一种复合的压力状态，可以在莫霍面附近造成形成含柯石英和金刚石的超高压变质岩的地质环境，其前是造成来自地幔向上压力过程的速率要大于地壳释放压力的地质过程的速率，并同时提出地深增压率的概念和在地质上的一些表征．最后结合桐柏—大别高压、超高压变质岩的地质事实提出一个高压、超高压变质成因的模型

DEPTH OF HIGH-PRESSURE AND ULTRA-HIGH- PRESSURE METAMORPHISM

Based on the measurement on compressibility coefficient of selected silicate minerals,combined with geolgical facts,it is suggested that a superimposed pressure caused by both load pressure and mantle derived pressure exists in the lithospheric crust-mantle boundary.The superimposed pressure may result in the formation of ultra-high-pressure metamorphics bearing coesites and diamonds near the Moho.The geological conditions in which the upward transfer of mantle derived pressure is greater than the release of crustal pressure are responsible for the formation of the superimposed pressure.The definition of the geopressure gradient with depth and its characters have been discussed.A genetic model for high-pressure and ultra-high-pressure metamorphics is introduced and exemlified by the Tongbai Dabie high pressure and Ultra high pressure metamorphics.