RHEOLOGICAL PARAMETERS OF CRUSTAL ROCKS AND CRUSTAL RHEOLOGY OF NORTH CHINA
ZHOU Yong-sheng HE Chang-rong (Institute of Geology and Tectonophysics Laboratory, CSB, Beijing 100029, China)
Rheological parameters and deformation mechanisms of rocks are the basis for estimating crustal strength by using frictional constitutive equations and power law creep equations. In the past 30 years, substantial progress has been made in high-temperature and high-pressure experimental studies, which provide a large numbers of data on rheological parameters of crustal minerals and rocks, as well as new insights into the deformation mechanisms. In this paper, we summarize systematically the existing experimental data, and study crustal rheology of North China by using these data combined with focal depth distributions in this region. The results show that the upper crust as represented by granite and low-grade metamorphic rocks is deformed in brittle faulting and frictional sliding regime, the strength of which is controlled by friction on faults; the middle crust comprising felsic-gneiss, as well as the upper layer of lower crust composed of intermediate granulite behave in plastic flow regime; the lower layer of lower crust consists of dry mafic granulite, which behaves in brittle-plastic flow transition regime. The composition and rheological stratification of the crust in North China may cause decoupling of different crustal layers and provide mechanical conditions for strong earthquake generation. In addition, they may also serve as the bottom boundaries for blocks of different scales.