Home – Home – Jornals – Russian Geology and Geophysics 2002 number 11

The picrite-dolerite ore association was well expressed at the orogenic stage of development of the Hercynides of the Zaisan-Gobi fold belt, separate parts of which are associated with Cu-Ni ore occurrences and deposits. Exemplified by the Kuolotong deposit (North Xinjiang, China), the main stages of its formation as a single ore-magmatic system have been shown: from sulphide-silicate liquation in an intermediate chamber to fractional crystallization of a sulphide melt in the ore-hosting intrusion. The fractional crystallization played a leading role in the formation of ores of varying composition (Ni-Fe, Fe-Cu, and abnormally cupriferous). Additional evidence is distribution in them of Pt, Pd, Au, and Ag, enriching the residual sulphide melt. The fact that Au dominates over Pd in the Kuolotong ores suggests considerably advanced fractionation of sulphide liquid during their formation, which corresponds to experimental data for these metals in sulphide systems. The isotope composition of sulphur in the ores is close to the meteorite standard, slightly deviating toward the heavy isotope. Halogen-bearing fluids little contribute to migration and concentration of noble metals. The petrologic and geochemical characteristics of the Kuolotong deposits, in combination with mineralogical and geochemical signatures of other ore-bearing intrusions of picrite-dolerite ore association, may be used for estimating the unclear ore potential of such intrusions.