BEHAVIOR OF METALS DURING FORMATION OF BASE METAL DEPOSITS

点击翻译按钮获取中文摘要

Magmatic fluid separated from hydrous magma has high salinity, and contains heavy metals and gaseous components such as CO_2. Magmatic fluids are believed to be responsible for the formation of hydrothermal ore deposits. Volatile components dissolved in fluid move into vapor phase, while salts and metals remain in liquid phase during boiling of fluids. However, metals of high concentration are occasionally found in vapor-rich fluid inclusion associated with high temperature hydrothermal system. Such vapor inclusions suggest that the behavior of metals under boiling hydrothermal system is more complex than it has been believed. In order to clarify the behavior of metals during boiling, newly designed high temperature autoclave was introduced in this study. Fractionation of Cu and Zn between coexisting vapor and liquid phases was determined to analyze concentration of these metals in fluid inclusions synthesized under boiling condition. Our result suggests that high concentration of copper occasionally found in vicinity of natural high temperature hydrothermal system is probably dissolved as sulfide complex. Synchrotron X-ray fluorescence was used as a technique to analyze individual fluid inclusion in present study. The quantification of this methodology was established to make up correction lines using synthetic fluid inclusions of known concentrations of metals. Hydrothermal experiments on the solubility of NaCl in the system NaCl-CO_2-H_2O were also conducted. Studies on the origin and nature of ore-forming fluid of the manto-type Cu deposit at the Andes area, Chile, and those of metamorphic water associated with contact metamorphosed bedded manganese deposit were conducted.