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Geochemical Characteristics and Sources of Ore‐forming Fluids of the Mayuan Pb‐Zn Deposit, Nanzheng, Shaanxi, China
Author(s) -
Shuwen LIU,
Ronxi LI,
Guoxiang CHI,
Rong ZENG,
Lingfang LIU,
Shun SHI
Publication year - 2015
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12478
Subject(s) - calcite , sphalerite , fluid inclusions , geology , dolomite , galena , quartz , gangue , mineralogy , carbonate , geochemistry , dolostone , mineralization (soil science) , meteoric water , pyrite , carbonate rock , sedimentary rock , metallurgy , hydrothermal circulation , materials science , paleontology , seismology , soil science , soil water
The Mayuan stratabound Pb‐Zn deposit in Nanzheng, Shaanxi Province, is located in the northern margin of the Yangtze Plate, in the southern margin of the Beiba Arch. The orebodies are stratiform and hosted in breciated dolostone of the Sinian Dengying Formation. The ore minerals are primarily sphalerite and galena, and the gangue minerals comprise of dolomite, quartz, barite, calcite and solid bitumen. Fluid inclusions from ore‐stage quartz and calcite have homogenization tempreatures from 98 to 337°C and salinities from 7.7 wt% to 22.2 wt% (NaCl equiv.). The vapor phase of the inclusions is mainly composed of CH 4 with minor CO 2 and H 2 S. The δD fluid values of fluid inclusions in quartz and calcite display a range from –68‰ to –113‰ (SMOW), and the δ 18 O fluid values calculated from δ 18 O quartz and δ 18 O calcite values range from 4.5‰ to 16.7‰ (SMOW). These data suggest that the ore‐forming fluids may have been derived from evaporitic sea water that had reacted with organic matter. The δ 13 C CH4 values of CH 4 in fluid inclusions range from –37.2‰ to –21.0‰ (PDB), suggesting that the CH 4 in the ore‐forming fluids was mainly derived from organic matter. This, together with the abundance of solid bitumen in the ores, suggest that organic matter played an important role in mineralization, and that the thermochemical sulfate reduction (TSR) was the main mechanism of sulfide precipitation. The Mayuan Pb‐Zn deposit is a carbonate‐hosted epigenetic deposit that may be classified as a Mississippi Valley type (MVT) deposit.