Lame parameter (lambda) and shear modulus (mu) are the most important, intrinsic, elastic properties of rocks. The Lame parameter lambda, which relates stresses and strains in perpendicular directions, is closely related to the incompressibility and contains a high proportion of information about the resistance to a change in volume caused by a change in pressure. Recent studies have emphasized the roles played by lambda in the discrimination of gas sands from carbonates and shale in sedimentary basins and in the seismic reflection of crustal fault zones. Here we analyze the equivalent isotropic elastic data of 475 natural rocks in order to characterize lambda values for common types of crystalline rocks in the Earth's crust and upper mantle and their variations with pressure (P), temperature (T), and mineralogical composition. When no partial melting, metamorphic reaction, dehydration, or phase transformation occurs, lambda of a crystalline rock as a function of P and T can be described by lambda = a + (d lambda/dP)P - c exp(-kP) - (d lambda/dT)T, where a is the projected lambda value at zero pressure if microcracks were fully closed; d lambda/dP is the pressure derivative in the linear elastic regime; c is the initial lambda drop caused by the presence of microcracks at zero pressure; k is a decay constant of the lambda drop in the nonlinear poroelastic regime; and d lambda/dT is the temperature derivative. The parameter lambda increases nonlinearly and linearly with increasing pressure at low (<similar to 300 MPa) and high (>similar to 300 MPa) pressures, respectively. In the regime of high pressures, lambda decreases quasi-linearly with increasing temperature with d lambda/dT values in the range of 1-10 x 10(-3) GPa/degrees C. Approaching the alpha-beta quartz transition temperature, quartzite displays negative lambda values. In the lambda-rho (density) and mu-lambda plots, the main categories of lithology can be clearly distinguished. The ultramafic rocks display systematic decreases in both mu and lambda with increasing the degree of serpentinization. Eclogites, mafic rocks (gabbro, diabase, mafic granulite, and mafic gneiss), and felsic rocks (granite, diorite, felsic gneiss, intermediate gneiss, and metasediments) are characterized by high, moderate, and low mu and lambda values, respectively. For pyroxene and olivine, both lambda and rho increase, but mu decreases with increasing the Fe/Mg ratios. In the plagioclase series, both lambda and mu increases with increasing the anorthite content. Increases in the contents of garnets, sillimanite, rutile, zircon, ilmenite, and spinel result systematically in an increase in rock's lambda and mu values. The present results provide improved constraints on the discrimination of composition for crustal and upper mantle rocks in terms of lambda and mu.
