Ascending Of Cu-Ni Sulfide Liquid In Magma Conduit Metallogenic Systems

Magma conduit system metallogenic theory,as a newly developed theory in the past few years,is powerful in interpreting the whole process of sulfide ore deposit genesis:Including origination of ore-bearing magma,partition of metal elements between silicate melt-sulfide liquid-mineral crystals,ascending of metallogenic materials in the crust,and emplacement of ore magma or sulfide-laden silicate melts in the crust.Furthermore,this hypothesis provides effective theoretical instruction for exploration of Cu-Ni-PGE ore deposits.Seems reasonable in most aspects as the theory is,its principal challenge lies in the difficulty for dense sulfide liquid to ascend to shallow level in the crust where the wall rocks are usually with far lower density than the sulfide liquid.By addressing the change of sulfide ore magma density and viscosity under the influence of different temperature,pressure,and adding in of various volume fractions of volatile fluid,as well as external driving forces through theoretical and empirical computation in combination with CFD(computational fluid dynamics)software,the author tries to point out the probable mechanisms for sulfide ore magma to be transported from deeper to higher level trough the less dense crust.To research the evolution of ore magma density and viscosity,I adopt predecessors' experiments results to calculate the ore magma density and viscosity using relevant theoretical and empirical formulas.Then I take advantage of the mixture turbulent flow model in the CFD module of FEM(Finite Element Method)numerical simulation software COMSOL Multiphysics to study the velocity field distribution in the conduit and its change with time while sulfide ore magma with various fractions of volatile bubbles rising up in the conduit under the propulsion of driving forces with different intensity.After comprehensive work,I propose that the density as well as viscosity of pure sulfide liquid would not experience dramatic change during ascending processes along the magma conduit,but may significantly decrease as consequences of the adding in of volatile bubbles.Consequently,it will become much more probable for sulfide liquid to move up.Besides,the tectonic stress in the wall rocks,overpressure caused by volatile and other stress may also forcefully drive the sulfide liquid up.By probing into the hydrodynamics of mixture of sulfide liquid and various content of volatile fluid flowing upward through numerical simulation,I suggest that it is possible for sulfide ore magma to overcome the force of gravity and the drag force from the conduit wall to rise up to shallow level as long as proper driving force is posed on it.Moreover,according to the calculation result from the simulating software,the required driving force is far from unrealistically great for the crust to provide.