Earth Science Frontiers ›› 2018, Vol. 25 ›› Issue (5): 237-250.DOI: 10.13745/j.esf.yx.2018-4-8

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The origin and significance of the differences in petrogenesis and mineralization of porphyry gold, copper and molybdenum deposits

SHU Sunping,LI Qiugen,LIU Shuwen,CHEN Yanjing   

  1. The origin and significance of the differences in petrogenesis and mineralization of porphyry gold, copper and molybdenum deposits
  • Received:2018-02-08 Revised:2018-04-17 Online:2018-09-15 Published:2018-09-15

Abstract: In this paper, we compare the similarities and differences among porphyry Au, Cu, and Mo deposits in tectonic setting, whole rock geochemical characteristics due to ore-causative intrusion, and in temperature, pressure and salinity of exsolved fluid and related alteration. To expound these differences, we reviewed metal geochemistry and magma/fluid source and evolution, which explained the collected whole rock geochemical data and p-T-X of exsolved fluid. The differences in geochemical behavior, especially sulfophile affinities of Au, Cu and Mo, control the elements distribution, transport and enrichment in the magmas. And various magmatism in different tectonic settings control the distribution of ore metals. Factors, such as magma source region, fractional crystallization during ascent, and intra-chamber magma evolution in the middle and upper crust, shape the magmas geochemical characteristics which affect the pressure and temperature of emplacement to cause fluid exsolution at various p-T-X. The contents of LILEs (Rb, Sr, Ba) and SiO2 in magmatic rocks can be used to determine mineralization types in general: porphyry Mo deposits prefer high Rb content; Ba is enriched in porphyry Mo-Cu deposits; and Sr content will be the highest in porphyry Cu-Au deposits. Compared to subduction setting, LILE content in ore-causative magmatic rocks should be higher in post-subduction environment, where ore potential can be indicated initially from the textures (porphyry, weakly porphyry, heterogranular, equigranular, etc.) of intermediate to silicic rocks.

Key words: porphyry deposits partition coefficient, magma evolution, fluid exsolution

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