'Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences'
Abstract
Gejiu is the largest polymetallic tin ore-field over the world. Kafang copper deposit is a main copper provider in Gejiu. There are two kinds of ore-body in Kafang copper deposit. One is stratiform-like ore-body, and the other is contact ore-body. The main wall-rock alterations comprise skarnization, actinolitization and phlogopitization. The analytical results of electron microprobe show that the clinopyroxene is diopside-andradite series. The end member of garnet is dominated by andradite and grossular, with minor spessartine and almandine. Fluid inclusion analysis indicate that the temperature of ore-forming fluid decreased significantly (260-360°C to 160 - 280°C) and the salinity of ore-forming fluid keeps constant basically ( 1.74% - 12.51% to 1.74% -11.93% ) from main mineralization stage to post mineralization stage. Hydrogen isotope analysis and oxygen isotope analysis show that the ore-forming fluid is dominated by magmatic water in the early stage, but in late stage, it could be mixed with magmatic and meteoric water. The compositions of sulfur isotope show that sulfur of stratiform-like ore-body was derived from Triassic basalt, yet both of Triassic basalt and Yanshanian granite provide sulfur for contact ore-body. The compositions of lead isotope show that the source of ore-forming material of stratiform-like ore-body is Triassic basalt, yet the source of lead of contact ore-body is Yanshanian granite
