부산대학교 도서관

In situ Raman spectra of aqueous [K.sub.2]W[O.sub.4]-HCl, [K.sub.2]W[O.sub.4]-HCl-NaCl, and [K.sub.2]W[O.sub.4]- C[O.sub.2]-NaCl solutions were collected at elevated temperature (T, 100-400[degrees]C) and constant pressure (P) of 30 MPa. The stretching vibration band of the W=O bond ([v.sub.1]) was analyzed to reveal the species of tungsten (W) responsible for the hydrothermal transport of W during mineralization. Results showed that monomeric tungstates with [v.sub.1](W=O) bands at ~930 and 950 [cm.sup.-1] are the dominant W species in weakly alkaline (room temperature, pH = 7.7) to near-neutral (room temperature, pH = 7.2) solutions under the investigated T-P conditions. Overall, the stability of polymeric tungstate species with [v.sub.1](W=O) bands at ~965-995[cm.sup.-1] decreases with rising temperature and was not detected at [greater than or equal to]300[degrees]C in moderately acidic solution (room temperature, pH = 4.9). However, increased fluid acidity and salinity obviously enlarged the temperature stability field of polymeric tungstate species. In highly acidic solution (room temperature, pH = 1.4), polymeric tungstates are the only stable W species even at 400[degrees]C. In the presence of 1.9 mol/kg NaCl, polymeric tungstate(s) can persist to at least 350[degrees]C in moderately acidic solution. Considering that 300- 350[degrees]C is the major W-mineralizing T range and W-mineralizing fluid is generally characterized by a moderately acidic nature, we propose that, in addition to monomeric tungstates, polymeric tungstates can also be important W species in some natural geological fluids that are responsible for the mineralization of W. Future studies of the W mineralization mechanism should take this issue into account.
1. Introduction Tungsten (W) deposit is generally a typical hydrothermal deposit. Construction of the mechanism for the formation of hydrothermal deposit needs knowledge on the species of the element of [...]