| Abstract:The porphyry deposits are mainly located in several intraplate fracture-magma belt. The ore-forming magma was formed as a result of remelting of mantle materials and crustai material in different proportions. Cu, Mo, Fe deposits were formed from magTna of mantle origin, while W, Sn, U deposits mahdy from magma of crustal origin. D1 and S1 of ore-related maffma in different kinds of deposits vary in a limited range. The hydrothermal fluid is amixture of magmatiC water and meteoric water. Salinity of fluids is generally high and can even reach 40一69 wt％NaCl equiv．in Cu and Sn deposits; nevertheless, in Au and W deposits, it is sometimes extremely low, and even as low as 2—3 wt％NaCI equiv．Hydrothermal fluid consists mainly of H2O, Na, K, Ca, Ci, F, SO42-and CO2. Fluid inclusion studes show that ore was formed in a weak reduction environment, and that although the temperature of the whole metallogenic process varied greatly, the ores were formed in a narrow temperature range: varying between 150℃and 400℃. The pulsating open and closed ore-forming system resulted in considerable drop of pressure, repeated boiling of ore fluid, wall rock alteration and precipitation of metallic minerals. |
