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EXPERIMENTAL RESEARCH ON RHEOLOGICAL BEHAVIORAS OF LOWER CRUST AND ITS SIGNIFICANCE OF TECTONIC EVOLUTION IN THE JUNCTURE AREA OF SHANXI, HEBEI AND INNER MONGOLIA PROVINCES, CHINA

Zhao jing1, Liu shun2   

  1. 1. China University of Geosciences, Beijing 100083; 2. Chendu Institute of Science and Techoology, 610059
  • Received:1998-06-20 Revised:1998-06-20 Online:1998-06-20 Published:1998-06-20

Abstract: High-pressure and high temperature experiments on basic and acid granulites sampled from the juncture area of Shanxi and Hebei and Inner Mongolia provinces show that, steady-state flow law obtained from these two kinds of granulites are ε=20.7exp(-288/RT)×△σ3.0 andε=10^6.59exp(-425RT) △σ3.02 respectively, and can be correlated with those from granulites exposed in Canadian continental shield. Under the condition of temperature at 700~1000℃ and confining pressure at 1.0~1.2GPa and strain rate at 10^-14S^-1 concerning lower crust, experimental rocks deformed in mainly ductility and ductile shear zones developed in some rocks. Pyroxene and feldspar are subject to undergoing dynamic recrystallization and oriented in lineation, while quartz was in static recovery. The result above can match with that observed from the field. The macro-rheology-models of lower crust show that one or more thicker lower-creep-strength-layers exist in lower crust with regard to thicked lithosphere as well as in upper mantle with regard to thinned one. Rheological behaviors of continental lower crust characteristic of lower-creep-strength layer of this kind can help lead to thicking and thinning of lithosphere.