Abstract:

 In this study, we provide a novel method which combines the technique of oremelting blocked by HCl（aq） and H2O2 with the ICPMS for the first time to determine the amount of Platinum metal group elements (PGE), siderophile elements and chalcophile elements in the typical ore in the East and West ore fields of Jinchanggouliang gold (copper) deposits. The experimental results show that the content of these elements in the ore is higher than the detection limit of the test technique, especially for the PGE. The geochemical evolution characteristics of these elements indicate the orebearing fluid having the magma properties. The characteristics of PGE prove the fact that the primitive mantlenormalized PGE shows a strong leftinclined fractional patterns, which is similar to the copperrich sulphide melt and nickelsulphide melt associated with mantlederived magma, and to the mantlederived basalt and carbonate melts, so we suggest that the orebearing fluid has the properties of mantle magma fluid. Considering the regional structural, magmatic and thermal events, and combined with the geochemical characteristics of reported typical porphyry copper (molybdenum) deposits, we may draw the conclusion that the orebearing fluid formed in the Mesozoic continental marginal environment, and the thermal dynamic source may have been derived from the underplating basaltic magma. The Pd/Pt and Pd/Ir ratios of Au and Curich ore samples are close to those of lowtitanium basalt and basaltic andesite for the oreforming stage, but the ratios of the Au and Cupoor samples are close to those of the mantle endmember for the early mineralization stage, which indicates the early orebearing fluid may directly come from the differentiation and crystallization of Mesozoic basalt magma, while the Au and Curich fluid may have been produced by the separation of the fluid from the supercritical fluidrich magma (low Ti magma), which was formed in the later evolution stage of basalt magma with contamination by crustal materials. The PGE geochemical activity in the orebearing fluid evolution process was related to the saturation of copper or sulfur (arsenic), that is, it was controlled by chalcophile elements or crystallized mineral facies of sulfides.

Key words: geochemistry, PGE, siderophile and chalcophile elements; , gold(copper) deposits, Jinchanggouliang, Inner Mongolia