DYNAMICS OF BASIC MELT COOLING DURING THE FILLING OF A FUNNEL-SHAPED INTRUSIVE CHAMBER

A nonstationary, nonisothermal model has been derived for the dynamics of the development of a magmatic system, in which magma fills a funne l-shaped intrusive chamber. The intrusion of magma into the crust occu rs when there exists in the magma generation source some excess pressu re, which exceeds the buoyancy of basic liquid in ultrabasic rocks. Th e average rates of the magma how at the entrance of the conduit to the chamber have been found to range between 0.02 and 20 m/s during the f ormation of large basic plutons. Three regimes of magma cooling have b een predicted during the formation of funnel-shaped chambers: (1) at h ow rates of 0.2-10 m(3)/s, the volume of the liquid core in the intrus ive body is less than 0.4 of its volume by the time magma has filled t he chamber, the average content of the solid phase in the liquefied me lt is about 0.4; (2) at flow rates of 10-100 m(3)/s, the volume of the liquid core in the intrusive body is 0.4-0.8 of its volume, the avera ge content of the solid phase in the liquefied melt is 0.3-0.25; (3) a t flow rates of 100-200 m(3)/s, the volume of the liquid core is 0.8-0 .9 with a solid phase content of 0.1-0.15 in it. Almost no superheatin g occurs in magma as it fills the chamber.