地质学中普遍采用的压力与深度转化方法是基于阿基米德定律,该定律适用于重力场中的静流体压力条件下的压力与深度关系.然而,由于岩石圈的高黏度与各向异性特性和构造差应力作用,决定了岩石圈内的压力分布和应力分布受多种因素影响.基于近期新发表的研究成果,介绍了从颗粒尺度压力差到岩石圈构造超压研究新进展,讨论了地质学中的压力与深度关系问题.近期研究表明,与静压状态下获得的压力分布与深度关系相比,在差应力条件下获得的变质反应压力和相变压力要复杂得多.在差应力条件下,从微观尺度的变质反应和岩石颗粒间尺度到不同地质体之间、地壳内部构造带和岩石圈尺度都存在局部压力非均匀分布(构造超压).在强烈隆升的高原地区,在高程差的重力势作用下也可以出现构造超压.这种压力非均匀的存在决定了变质反应压力和矿物相变压力不等同于静岩压力.热-力学耦合数值模拟结果显示,由于偏应力作用,在大陆碰撞造山带42 km深度,构造超压达到2.2 GPa,局部压力达到3.4 GPa,远高于平均静岩压力.由此推测,在40～50 km深度,就有可能出现高压-超高压变质作用.因此,根据变质反应和矿物相变确定的压力不能直接换算成岩石圈深度.%The Archimedes' formula is a first order approximation to the calculation of the depth of lithosphere based on rock column pressure in geology.This formula was derived from the principle of force balance for static fluids in the gravity field and relates pressure with depth.However,in deforming regions of the lithosphere,distribution of pressure and stress is affected by high viscosity and anisotropy of lithos as well as deviatoric stress that develops deformation,which will have an additional effect on the value of pressure.In this paper we introduce new progresses in the research on from grain scale pressure variations to tectonic overpressure of lithosphere,and discuss the relationship between pressure and depth based on reviewing published data.Recent studies show that the metamorphic pressure and phase transition pressure are more complicated under differential stress condition compared with that of lithostatic pressure.Pressure variations (tectonic overpressure),in terms of micro-scale metamorphic reaction,rock grain size and among different geological bodies,exist under differential stress condition in the tectonic zone of crust and lithosphere.On the continental plateaus,the deviatoric stress and tectonic overpressure could be produced by lateral variations in the gravitational potential energy.The existence of pressure variations and tectonic overpressure in the lithosphere means that the metamorphic pressure or phase transition pressure is not the same as lithostatic pressure.The thermo-mechanical coupling numerical simulations show that,under the effect of deviatoric stress,significant tectonic overpressure occurs in a depth of ～42 km at 2.2 GPa,and the maximal pressure is about 3.4 GPa,much higher than the lithostatic pressure;this implies that at the depth of 40-50 km,ultrahigh-pressure metamorphic facies fields may be found.Thus,pressure achieved by metamorphic reaction and phase transition does not translate directly into the depth of lithosphere.
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