A Preliminary Study on Fluid Inclusions and Mineralization of Xitieshan Sedimentary-Exhalative (SEDEX) Lead-Zinc Deposit

• Published in: 地质学报（英文版） 2008, Vol.82 (4), p.838-844
• Main Authors: WANG Lijuan, ZHU Xinyou, WANG Jingbin, DENG Jiniu, WANG Yuwang, ZHU Heping
• Format: Article
• Language: English
• ISSN: 1000-9515
• DOI: 10.3321/j.issn:1000-9515.2008.04.014

P5; The Xitieshan lead-zinc deposit is located at the northern margin of the Qaidam Basin,Qinghai Province, China, and had developed a complete marine sedimentary-exhalative system. Ourpreliminary study of ore-forming fluids shows that fluid inclusions in quartz from altered stockworkrocks that represent the pipe facies have a wide range of temperature and salinity. The intense fluidactivities are characteristics of the pipe facies of the exhalative system. Fluid inclusions in carbonatesnear the unstratified ore bodies hosted in the thick-bedded marble which represents vent-proximalfacies are large in size and have moderate to high temperatures. They represent unerupted sub-seafloorfluid activity. Fluids in altered stockwork rocks and carbonates have similar H2O-NaCl-CO2 system,both belonging to the sedimentary-exhalative system. The fluids migrate from the pipe facies to theunstratified ore bodies. Boiling of the fluids causes the separation of CO2 vapor and liquid H2O. Whenthe fluids migrate into the unconsolidated thick-bedded marble, the escape of CO2, decreasingtemperature and pressure as well as some involvement of seawater into the fluids result in the unmixingof fluids with high and low salinity and deposition of ore-forming materials. The two unmixed fluids were trapped in unconsolidated carbonates and the ore-forming materials were deposited in theunconsolidated carbonates to form the sedimentary-exhalative type unstratified ore bodies. The ore-forming temperature of unstratified ore bodies is up to high temperature indicating that there is a hugeore-forming potential in its deep.