蔡家营铅-锌-银矿床的稳定同位素地球化学研究  

STUDY ON STABLE ISOTOPIC GEOCHEMISTRY OF CAIJIAYINGPb-Zn-Ag DEPOSIT,HEBEI PROVINCE,CHINA

作　　者：黄典豪[1] 吴澄宇[1] 张长江 

机构地区：[1]中国地质科学院矿床地质研究所,河北地质矿产局第三地质大队

出　　处：《地球化学》1997年第4期24-25,共2页Geochimica

基　　金：地质矿产部定向基金

摘　　要：河北蔡家营矿床是大型中温热液充填－交代脉型铅－锌－银矿床。其硫化物的δ３４Ｓ值为２．２‰－７．８‰，同世代共存的１０个硫化物对的Δ３４Ｓ值表明，Ｆｅ－（Ｚｎ、Ｐｂ）－Ｓ系统的硫同位素非平衡分镏占主导，硫是岩浆（为主）与老变质岩层硫的混合来源。石英及其流体包裹体的δ１８ＯＳＭＯＷ和δＤＳＭＯＷ值（‰）按混合模式计算表明，成矿流体为混合的岩浆和大气降水，早期成矿流体以岩浆为主，尔后则变为以大气降水占优势。与方解石平衡ＣＯ２的δ１３ＣＣＯ２值为－３．０‰──４．８‰，表明成矿流体中的混合碳为岩浆碳和萃取自老变质岩层内大理岩的碳。矿质沉积化学环境ｌｇｆＯ２＝－３６．８──３８．５，ｌｇｆＳ２＝－１０──１３，ｐＨ≈５，属于硫逸度高而氧逸度较低的弱酸性还原环境。The Caijiaying large-scale Pb-Zn-Ag deposit is a mesothermal filling-metasomatic vein deposit 34 S values measured on 49 sulfide samples range from 2.2% - 7.8%, with an average of 5.2%. Among 34S values calculated on coexisting sulfide pairs, there are not only negatives but also positives (relative low), suggesting that a non - equilibrium sulfur- isotopic fractionation dominated during the mineralization process. With the fact of absence of sulfate mineals. HS- and S2-. are. considered to be the main sulfur. species in the hydrothermal system, and sulfur isotopic fractionalion between HS- and pyrite is insignificant at the temperature range ( 1 80- 320) of mineralization.An...average 34Spv value(+ 4.6) of 1 5 pyrite samples may be approximately regarded as the 34Ss of the system Therefore,the sulfur source of the ores is mainly derived from granitic magmas. 18 O (SMOW) values measured on 6 quartz samples are between 13.1%and 14.4%ll,18OHo(SMOWy), .,-d tl tl i. .qlilibll- .ith tbl qllllb, - lltll.. 2.0/lll ld 8.3/lll, ald d D ll. (SMOW) values between-76 % and -109 %. - This demonstrates a magmatic - meteoric mixed water origin for the mineralizing fluid, based on calculations of water - wall rock isotopic interactions. The magmatic water components dominated in the early stage of the mineralizadtion, while the meteoric water dominated in the late stage. . 13 Cco. (PDB) values are from -3.% to -4.8%, calculated on measured values of calcites,supporting a mixed carbon source between those from magmatic origin and those extracted from marble in metamorphic sequence. The physico-chemical parameters of the mineralizing fluid are estimated to be lgfo2 -36.8--38.5, lgfs2 - 10- - 13, lgfco2 3.0 and pH 4.4-5.4, indicating a weak acid, reduce and high sulfur environment during the ore---formation.

关 键 词：铅锌矿床 银矿床 稳定同位素 地球化学 

分 类 号：P618.404[天文地球—矿床学] P618.520.4[天文地球—地质学]