云南保山核桃坪铅锌矿床同位素地球化学特征

Characteristics of Isotope Geochemistry of Hetaoping Pb-Zn Ore in Baoshan,Yunnan Province,China

核桃坪铅锌多金属矿床是云南保山地块近年来所发现的一个大型多金属矿床,地勘工作显示该类型矿床在该区具良好的找矿前景。对矿区围岩及矿石矿物的硫同位素组成、铅同位素组成与氢、氧同位素进行系统研究与对比,结果表明:矿床中的δ34S‰的变化区间较窄,在+2.9‰～+6.6‰之间,峰值集中于+4.5‰～+5.5‰,具有深部岩浆硫同位素组成特征;硫化物单矿物(闪锌矿和方铅矿)及矿石铅的铅同位素组成以高μ值和低放射性成因铅为特征,显壳源铅的特征,暗示矿床成矿物质以壳源为主;与硫化物共生的石英δ18OV-SMOW变化范围在+10.5‰～+12.1‰之间,平均值为+11.3‰,极差为1.6‰,δDV-SMOW值为-109‰～-91‰,平均值为-100.8‰,极差为-8‰,表明成矿流体主要来源于深部的岩浆水,可能遭受了后期的大气降水或者是底层建造水的混合。结合矿床地质特征,笔者认为本矿床的成矿物质主要与深部隐伏岩体有关,属于与深部岩浆热液活动有关的夕卡岩型矿床。

Hetaoping Pb-Zn polymetallic deposits is a large polymetallic deposit which was found in Baoshan block in recent years. There are two large-scale deposits, five medium-small-scale deposits and more than 10 ore occurrences having been explored with the new round of land resources survey project since 1999, including the mineralization of Pb, Zn, Cu, Au, Ag, Fe and so on. In which, the Hetaoping Pb-Zn-polymetallic deposits has been evaluated as a large-scale deposit and there is a very good exploration prospects for the same type deposit in Baoshan region with the geological survey. Based on studying and comparison on sulfur, lead, hydrogen and oxygen isotope composition of ore minerals and wall rocks in the deposit, it shows that： （1） sulfur isotope is in the range from ＋ 2. 9%o to ＋ 6. 6%0 with the peak value between ＋ 4. 5%0 and ＋ 5.5%0, showing the characteristic of source of deep magmatic sulfur; （2） There are high Ix values with low radiogenic lead for single mineral of sulfide （sphalerite and galena） and ores, showing the significant features of crust-derived lead, and implying that metallogenic material may mainly come from the crustal resources; （3） Oxygen isotopic compositions of quartz in ores are in the range from ＋ 10. 5%0 to ＋ 12. 1%o with an average of ＋ 11.3%o and a variance of 1.6%o. The hydrogen isotopic compositions of quartz in ores are in the range from -109%o to -91%o with an average of -100. 8%o and a variance of -8%c, indicating that the ore- forming fluids were mainly derived from the deep concealed magmatic activities and mixed with meteoric water or shallow-seated water. Combined with the geological features in the deposit, it is suggested that the major metallogenic material is related to the concealed rocks and the deposit is belong to a typical skarn-bound hydrothermal deposit.