Abstract:

 The three most important elementary factors for the formation of largesuper large magmatic sulfide deposits are that (1) large amount of mantlederived magmas participate in the formation of the deposits, that (2) magmatic evolution results in sulfide immiscibility, and that (3) the sulfides concentrate in a limited space. However, the superlarge magmatic NiCu sulfide deposits over the world have been found in small maficultramafic intrusions, except for the Sudbury deposit. The studies in the past 10 years indicated that the intrusions hosting superlarge magmatic sulfide deposit occur in magma conduit systems. For example, many of the large and superlarge magmatic sulfide deposits in China, including Jinchuan, Yangliuping, Kalatongke, and Hongqiling, occur in the magma conduit systems. The magma conduit system as an open system provides a perfect environment for extensive concentration of immiscible sulfide melts. The recent studies indicated that the magmatic sulfide deposits related magma conduit systems in the world occur along deep regional faults. Origin of the large amount of mantlederived magma is closely associated with mantle plume, continental rift, or post orogenic extension. Although it has been confirmed that sulfide immiscibility results from crustal contamination, the grades of the sulfide ores are also related to natures of the parental magmas, ratios between silicate magma and immiscible sulfide melt, reaction between the sulfide melts and the new injected silicate magmas, and fractionation of the sulfide melt. The field relationships of the sulfide containing intrusion and sulfide ore body are controlled by geological features of the hosting wallrocks. In this paper, we attempt to demonstrate the general features, formation mechanism and geological background, and significance of the magmatic sulfide deposits occurring in magmatic conduit system, which are very important for the further researches and exploration of this type of magmatic sulfide deposits.

Key words: magmatic NiCu sulfide deposit, magma conduit system, sulfide immiscibility, tectonic extension