Gold-Rich Mesoproterozoic Chimneys from Xinglong in Hebei and Implications for the Formation of Gold
REN Haojia LI Jianghai FENG Jun NIU Xianglong (School of Earth and Space Sciences,Beijing,100871)
Well-preserved Mesoproterozoic chimneys and mounds were recovered from the Gaobanhe SEDEX type polymetallic sulfide deposits in Xinglong, Hebei Province, North China. Electron microprobe measurement shows the chimneys have high gold contents. The highest content of gold among 74 testing points is up to 4560 μg/g. Gold contents in different minerals and different types of pyrite reveal apparent differences. Gold-bearing assemblages are dominated by idiomorphic pyrite, which were formed during the late-stage hydrothermal activity. Analyses of fluid inclusions in calcite, quartz and sphalerite show that precipitation of gold occurred at about 170 ℃, which also represents the lower temperature limit of chimney formation. This study provides direct proof for the relationship of exhalation and gold formation, indicating that gold precipitation is closely related to late-stage, low-temperature hydrothermal fluids.