Zinc, copper, and strontium isotopic variability in the Baiyangping Cu–Pb–Zn–Ag polymetallic ore field, Lanping Basin, Southwest China  

作　　者：Caixia Feng Shen Liu Guoxiang Chi Xianwu Bi Ruizhong Hu Ian MCoulson 

机构地区：[1]State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,229 Taibai Road,Xi’an 710069,China [2]Departments of Geology,University of Regina,3737 Wascana Parkway,Regina,SK S4S 0A2,Canada [3]Institute of Geochemistry,Chinese Academy of Sciences,99 Lincheng Road,Guiyang 550002,China

出　　处：《Acta Geochimica》2021年第4期557-574,共18页地球化学学报（英文）

基　　金：financially supported by General Project of Natural Science Foundation of Shaanxi Province (2020JM-423)。

摘　　要：The Baiyangping Cu-Ag polymetallic ore district is located in the northern part of the Lanping-Simao foreland fold belt,between the Jinshajiang-Ailaoshan and Lancangjiang faults,and the deposit can be divided into eastern and western ore zones.Based upon microscope observation of ore minerals and analysis of zinc,copper,and strontium isotope composition,we conclude that:(1)the zinc isotopic compositions of sphalerite from the eastern and western ore belt of the Baiyangping polymetallic ore deposits are enriched in both the heavy(-0.09‰ to+0.15‰) and light(-0.19‰ to-0.01‰)zinc isotopes.Rayleigh fractionation is likely the additional factor controlling the observed temporal and spatial variations in zinc isotopes in the two studied ore zones.The zinc isotopic composition in the Baiyangping polymetallic Pb-Zn deposits may have the same fractionation as that of magmatic-hydrothermal,VHMS,SEDEX,and MVT deposits,as demonstrated by geological and other geochemical evidence;(2) the range of δ^(65)Cu in massive tetrahedrite is from-0.06‰ to+0.12 ‰ that relates to the early stages of ore-formation,which are higher than that of venial chalcopyrite(from-0.72‰ to-0.07‰)formed at a late ore-forming stage in the western ore belt.Different ore-forming stages and alteration or leaching processes are likely the main factors controlling the observed variations in copper isotopes in the western ore zone;(3) the ^(87)Sr/^(86)Sr value of hydrothermal calcite in eastern(0.7080-0.7093) and western(0.7085-0.7113) ore belt suggested that mineralization of early calcite,with^(87)Sr/^(86)Sr values much higher than in ancient Late Triassic seawater,may be related to recrystallization from a radiogenic Sr-rich or silicifying fluid,either from the strata that the ore-forming fluid flows through or from other fluids.

关 键 词：Zn-Cu-Sr isotopic variation Cu-Pb-Zn-Ag poly-metallic ore deposit Baiyangping Lanping Basin 

分 类 号：P618.2[天文地球—矿床学]