扬子板块北缘马元铅锌矿床两类矿石地球化学特征及其对成矿作用的制约  

Geochemical characteristics of two Pb—Zn ores from Mayuan Pb—Zn deposit on northern margin of Yangtze Plate and constrains on ore-forming mechanism

作　　者：刘淑文[1,2] 李荣西[1,2] 曾荣[1,2] 李兴[1] 

机构地区：[1]长安大学地球科学与国土资源学院,西安710054 [2]国土资源部岩浆作用成矿与找矿重点实验室,西安710054

出　　处：《世界地质》2015年第4期984-992,共9页World Geology

基　　金：中国地质调查局项目(1212011121117);国家自然科学基金项目(41173055);中央高校基金项目(310827153407)联合资助

摘　　要：对马元铅锌矿白云石-硫化物型和重晶石-硫化物型矿石中的热液矿物白云石和重晶石的同位素和稀土元素地球化学特征对比研究表明,白云石的δ^(13)CPDB为-2.51×10-3~0.93×10-3,δ18OSMOW为17.55×10^(-3)~23.24×10^(-3),说明成矿流体中碳、氧来源于震旦系碳酸盐岩的溶解;锶同位素组成(0.711 46)表明Sr来源以壳源锶为主,可能与富放射性锶的上覆碎屑岩或下伏基底变质火山岩有关;稀土元素具有明显的正Eu异常(δEu平均为1.415),表明白云石-硫化物型矿化流体具有盆地中循环热卤水特点。重晶石的硫同位素(平均为33×10^(-3))具有富重硫且分布均一的特点,暗示硫可能来源于富集重硫的单一海相硫酸盐;Sr同位素(0.709 18~0.709 71)特征表明其来源以海水锶为主,有少量壳源锶加入;稀土元素具有明显负Ce异常(δCe平均为0.255)和正Eu异常(δEu平均为1.43),表明重晶石--硫化物型矿化有关的流体可能是海水(或大气降水)与盆地循环热流体混合的结果。白云石--硫化物型矿石和重晶石-硫化物型矿石的沉淀可能是盆地中循环热卤水与海水(或大气降水)两种端元组分以不同比例混合的结果。This paper mainly researches the geochemical characteristics of isotope and REE of hydrothermal dolomite and barite from dolomite-sulfide ore and barite-sulfide ore of Mayuan Pb--Zn deposit. The result shows that the δ13CPDB,δ18OSMOWand87Sr /86 Sr values of dolomites are- 2. 51 × 10^-3~ 0. 93 × 10^-3,17. 55 × 10^-3~ 23. 24 ×10^-3and 0. 711 46,respectively,indicating the C,O may derive from the dissolution of Sinian carbonates,and the Sr derived from crust,such as the basement and the Paleozoic clastic rocks rich in radioactive strontium. The REE patterns of the dolomites are with obvious positive anomaly of Eu（ δEu average of 1. 415）,indicating the dolomite-sulfide ore-forming fluid characterised by basinal hydrothermal fluid. The δ34S values（ average of 33 × 10^-3） of barite are enriched in34 S and narrowly distributed,implying that the sulfur may have been derived from marine sulfate. The87 Sr /86 Sr ratios（ 0. 709 18 and 0. 709 71） of barite also indicate that the Sr is mainly derived from seawater with little from crust. The REE patterns of the barites are with obvious negative anomaly of Ce（ average δCe of0. 255） and weak positive anomaly of Eu（ δEu average of 1. 43）,suggesting that the barite-sulfide ore-forming fluid might be seawater（ or meteoric water） mixed with basinal hydrothermal fluid. The precipitation of the dolomitesulfide ore and the barite-sulfide ore might be related to the fluid mixing of basin hydrothermal fluid and seawater（ or meteoric water） at different ratios.

关 键 词：同位素 地球化学特征 成矿机制 马元铅锌矿 扬子板块 

分 类 号：P618.4[天文地球—矿床学] P595[天文地球—地质学]