| Located respectively in the mineralization belts of Daxing’anling and Middle-lower Yangtze River, Wunugetushan Cu-Mo porphyry deposit and Matou Mo-Cu porphyry deposit, which is one of16metallogenic belts in China, are characterized by hydrothermal alteration and geologic feature of porphyry ore deposit. The paper based on the migration characteristics of the elements in the altered rocks in the process of hydrothermal alternation, immobile element, gains and losses of elements and qualitative change of metallogenic system were discussed. And then, the paper tried to reveal disciplines of element geochemical behavior and distribution in the metallogenic system of porphyry-type, In order to provide reference and demonstration for deep ore prospecting. The study results showed that:1. The mass migrations of elements in different altered biotite granites of Wunulagetushan deposit were calculated. The results demonstrated that mass migration of different elements show certain regularity within the range of mineralized alteration from potassic, phyllic to propylitic alteration. Compared with least-altered rocks, Cu, Mo, Au, Ag, W, Sn, As, F, Hg, S were obviously enriched, but CaO, Na2O, TiO2, Ba, Sr, Rb and REE depleted, Besides, REE were not always inactive in all hydrothermal deposits.2. The mass migration calculation results of elements in different altered rocks of Matou deposit showed that:1) In the process of Mo-Cu mineralized alteration, the major elements occurred gains and losses in various degree, and the migration regularity is obvious. In granodiorite porphyry, the major elements shows gains of K2O, SiO2, CaO, H2O from potassication zone, sericitization zone to propylitization zone, whereas the obvious loss of Na2O. In siltstone, altered rocks are obviously depleted in Na2O, CaO, MgO, Fe2O3, H2O+, and the migration quantity of major elements in pyrite-molybdenum mineralization siltstone is larger than that in propylitization;2) ore-forming elements such as Cu, Mo and associated elements Au and Ag were obviously gained but Ba, Sr, Th, Li lost, which differed in granodiorite porphyry and siltstone. In spite of certain fractional distillation, REE were totally inactive.3. In Matou deposit, the spatial corresponding relationships between elements mass migration characteristics of elements and altered ore-body reflected that:1) in the process of hydrothermal alternation, elements mass migration and distribution were closely related to the geochemical character and geochemical environment;2) to the deposits in granodiorite porphyry, Na2O, CaO, MgO, Ba, Sr were lost, and K2O, Rb, W, Au, Ag, Pb, Zn, Mo, Cu, S were gain, and the transfer migration of CaO was not obvious; to the deposits in sandstone, Fe2O3, CaO, Na2O, FeO, K2O, Ba, Sr, Rb were obvious lost, and MgO, W, Au, Ag, Pb, Zn, Mo, Cu, S were enriched.3)in the process of hydrothermal alternation,Na2O MgO, Fe2O3, Ba, Sr were obviously lost, but ore-forming and associated elements such as Mo, Cu, Au, Ag, S were gain.4. The assessment of quality change in Matou deposits by inactive elements, showed that the quality change of granodiorite porphyry showed net gain, and that of siltstone showed net loss, the amount of loss was higher in total in Matou mineralization system. It suggested that the mineralization of Mo-Cu was included in negative system, which could instructed the sphere of geochemical influence. And it was concluded that the quality change of the mineralization system was mainly caused by the gains and losses of the major elements. The research conclusion can make a solid step toward the quantification on geochemical exploration methods and.provide one of the necessary ways of the quantitative evaluation on the prospecting potential of deep deposits. |
PDF Full Text Request