Abstract:

Temperature and stress of country rock are obtained by the simulation of the temperature and stress when magma emplaced. The quantitative relationship between heat field and condensation contraction joint are established by integrated application of strain energy and surface energy theory. The fracture parameters are assessed quantitatively. Consequently, the development law of contraction joint is concluded in metamorphic belt. The metamorphic thickness increases when the intrusive thickness increases, while no metamorphic belt forms when the intrusive thickness is less than 20 m, by the study of the contact metamorphic belt in north slope of Gaoyou sag. Thermal stress decreases with the increasing distance from the intrusive rocks. Condensation contraction joints are chiefly extensive near the intrusive rock and the maximum of crack linear density is about 13 cracks/m. Away from the intrusive rock，the density of fracture line rapidly decreases, especially  3-6 linear density of cracks/m in the metamorphic belt edge. Overall, the upper metamorphic permeability is slightly better than that of the lower one. The maximum porosity of condensation contraction joints lies in the most thickness of the intrusive rocks, and short axis direction of crack penetration is similar to vertical direction，while its permeability is greater than that of the long axis. The validity of this simulation is testified by rock core statistics.

Key words: condensation contraction joints, thermal stress, strain energy, surface energy, porosity, permeability