Abstract:

Despite of special attentions drawn to mafic intrusions and their relations to mineralization, many scientific issues related to them remain in ambiguity till now. Based on the new field observations and the theoretical analysis, a complexity fluid dynamic model is proposed to attempt an integrated interpretation of ore deposit geology, petrography, and mineralogy of the magmatic iron deposit. Given the behavior of a magmatic mineral system being decided by strong interactions between the melt and fluidsubsystem, the successive changes of physical properties of the system would induce a variety of nonlinear modification in the system. (1) Before that there is not significant crystallization in the meltsubsystem, the orebearing fluid migrates up through the pervasive percolation, and induces oreinduced intrusion with hidden igneous layering and concordant ore bodies with disseminated structure. In such a condition, the orebearing fluid migrating up in a high speed could result in mineralization in the whole magmatic intrusion. The orebearing fluid migrating up with a lower speed could also lead to intense differentiation of a magmatic body, but the oreforming metals will not be concentrated to the marginal parts of the intrusion. (2) If the intrusion is consolidated partly (for instance, a half), the orebearing fluid may be transported on large scale only to the unconsolidated centre of the intrusion, in which the doublediffuse convection is caused, and obvious rhythmic sequences and concordant massive ore bodies are produced. (3) When the magmatic intrusion is cooled to complete consolidation, if the fluid overpressure is high enough or the farfield stress field is in action, the consolidating intrusion will be ruptured near the previous conduits. Under such circumstances, the orebearing fluid ascend to form the discordant ore body. (4) After complete consolidation of magma intrusion, subsequent invasion ore fluid can migrate along the contact zone between the layered intrusions and the country rock in the bottom, forming a new type of tabular ore or ore nests, even skarn ore bodies. (5)Sulfiderich fluid may also ascend in succession with the oxiderich fluid, facilitating the generation of sulfide ore body. This analysis is broadly in line with the actual situation in Panxi, and thus it can be a conclusion can be drawn. (1) Whether the magma intrusions become ore intrusions depend on the input of ore fluid, rather than magmatic differentiation. (2) Differential characteristics of ore intrusions are the results of the ore fluid input, rather than the causes.(3)Mafic magmatic system is a complex dynamic system. Ore fluid input is the root cause of its nonlinear behavior change. (4)The Metallogenic system of mafic magma in Panxi include concordanttype (including massive subtype and disseminated subtype two subtypes), discordanttype, skarntype iron ore subsystem, disseminated and massive sulfide mineralization subsystem. (5) In Panxi area, iron ore body is not only located in the layered rock, exploration potential also resides in the country rock underlain. There is even potential to discovering massive sulfides.

Key words: layered intrusion, magmatic iron deposit, mineral system, transmagmatic fluid, fluid dynamics, Panzhihua in Sichuan Province