Geochemical Characteristics and Sources of Ore-forming Fluids of the Mayuan Pb-Zn Deposit, Nanzheng, Shaanxi, China

• Published in: Acta geologica Sinica (Beijing) Vol. 89; no. 3; pp. 783 - 793
• Main Authors: Shuwen, LIU, Ronxi, LI, Guoxiang, CHI, Rong, ZENG, Lingfang, LIU, Shun, SHI
• Format: Journal Article
• Language: English
• Published: Richmond Blackwell Publishing Ltd 01.06.2015; Wiley Subscription Services, Inc; Chang'an University, Xi'an 710054, Shaanxi, China; Key Laboratory for the study of Focused Magmatism and Giant Ore Deposits, MLR Xi'an 710054,Shaanxi, China%University of Regina, Regina, SK, S4S 0A2 Canada%Geophysical and Geochemical Exploration Corporation of Northwest Geological Exploration and Mining Bureau for Nonferrous Metals, Xi'an 710086, Shaanxi, China%Chang'an University, Xi'an 710054, Shaanxi, China
• Edition: English ed.
• Subjects: Calcite; Deposits; display; Fluid dynamics; Fluid flow; fluid inclusion; Fluid inclusions; Fluids; Lead (metal); Mayuan Pb-Zn deposit; northern; ore-forming fluids; organic matter; Quartz; Shaanxi; 地球化学特征; 密西西比河谷型; 成矿流体来源; 热化学还原反应; 铅锌矿床; USA, Mississippi Valley; China, People's Rep., Shaanxi Prov; organic matter; ore-forming fluids; fluid inclusion; Shaanxi; Mayuan Pb-Zn deposit
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/1755-6724.12478

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℃ 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_2S.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.