广西武宣县盘龙铅锌矿矿床成矿地球化学特征

摘要

盘龙铅锌矿是桂中地区典型的大型铅锌矿床,它位于广西大瑶山西侧铅锌多金属成矿带南段.为了确定该矿床成矿流体性质和成矿金属来源,作者系统研究了矿床的稀土元素、硫铅同位素和流体包裹体特征.研究结果表明:矿石和围岩的ΣREE较低,LREE富集、具有显著的Eu正异常和弱Ce负异常；矿石的硫同位素除了3件黄铁矿样品δ34SV-CDT为-17.90×10-3、-21.00×10-3和-20.60×10-3,其它硫化物的δ34SV-CDT均落在-7.10×10-3～7.70×10-3之间,而重晶石样品的δ34SV-CDT较高,达17.3×10- 3～29.2×10-3,硫同位素分析结果暗示成矿物质来源于深源岩浆和泥盆纪海水的共同作用；矿石的铅同位素206pb/204pb、207pb/204pb和208pb/204pb的变化范围分别为18.376～18.438、15.763～15.852和38.763～39.060,相似的铅同位素特征表明矿石的来源和成因是均一的、相同的,并且具有壳源的特征.喷流成矿期成矿流体均一温度属中-低温(166～289℃)、低盐度(4.01％～14.07％)、低密度(0.804～0.955 g/cm3),成矿流体属于H2O-NaCl体系.综合矿床地质和地球化学特征可知,盘龙铅锌矿床显著区别于MVT型铅锌矿,应属于海底喷流-沉积型铅锌矿.%The Panlong lead-zinc deposit in the central region of Guangxi Province is a typical giant lead-zinc deposit, lying in the southwestern side of the Dayaoshan lead-zinc mupltimetal zone in China. The REE, S isotope, Pb isotope and fluid influsion geochemistry were discussed for understanding the source of the ore metal and the characters of ore-fluids in Panlong lead-zinc deposit. The results show that the low ΣREE and enriched LREE of the ore and wall rock pronounce the positive Eu anomaly and weak negative Ce anomaly. Most of sulfide δ34Sv-CDT values range from -7.1X10-3 to 7.7X10-3 , except for those of three pyrite samples with 17.9X10-3, -21X10-3 and -20.6X10-3, and those of barite samples range from 17.3 X 10-3 to 29.2 X 10-3, which indicates that the sulfur of ore is mainly derived from the mantle and the sea water. The Pb isotope analyses reveal that the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of the ore lead are 18.376-18.438, 15.763-15.852 and 38.763-39.060, respectively, which indicates that they have homogeneous, same source and geneses of Pb, and the lead shows characteristics of the upper crust lead. In sedimentary exhalative stage the ore-forming fluid is an H2O-NaCl system, with medium to low temperature (166-289 °C), low salinity (4.01%-14.07%) and low density (0.804-0.955 g/cm3). The geological and geochemical characteristics of the deposit lead to a conclusion that the Panlong lead-zinc deposit belongs to SEDEX deposit and is notably different from MVT deposit.