白银厂铜多金属矿田微量元素和稀土元素地球化学研究

GEOCHEMISTRY OF MINOR EIEMENTS AND RARE EARTH ELEMENTS OF THE BAIYINCHANG GU-POLYMETALLIC ORE FIELD,GANSU PROVINCE

与日本黑矿及现代海底火山岩为主岩矿床相比,白银厂矿田各类矿石,尤其是块状Zn—Pb—Cu矿石具有最高的As和Bi含量,比较高的Ga、Cd和Au含量,以及较高的Au/Ag和Co/Ni比值。该矿田矿石的Au含量与闪锌矿中铁含量呈负相关关系。小铁山矿床闪锌矿与日本黑矿的闪锌矿微量元素特征很相似。矿田各类矿石REE型式(pattern)与细碧角斑岩类岩石基本相似,这说明矿石与岩石的物质来源基本一致。研究和对比表明,火山成因块状硫化物矿床黄铁矿的Co、Se含量和Co/Ni比值有随矿床年龄变年轻而降低之趋势。

In comparison with ores from Kuroko deposits in Japan and modern seafloor volcanic-hosted deposits in the world,various ores from the Baiyinchang orefield, especially the massive Zn-Pb-Cu ore, have the highest As and Bi contents, and relatively high Ga, Cd, and Au contents as well as Co/Ni and Au/ Ag ratios. Au contents of ores from the field are negatively correlated with Fe contents of sphalerite from the ores. Sphalerite from the Xiaotieshan deposit of the field is similar to that from Kuroko deposits in Japan in minor elements. REE patterns of ores from the Baiyinchang ore field is comparable to those of spilite-keratophyre rocks from the field, suggesting that the source of the ores in the field is roughly consistent with that of the rocks. Investigation and comparison indicate that Co and Se contents and Co/Ni ratios of pyrite in volcanogenic massive sulfide deposits tend to decrease with the decrease of their ages.