北武夷梨子坑火山盆地流纹斑岩与铅锌矿的成因关系

摘要：梨子坑火山盆地位于北武夷中生代月凤山-梨子坑火山岩带东段，已知铅锌（铜、银）矿体或矿化呈细脉-浸染型、脉状，产于流纹斑岩脉的内外接触带及其外侧围岩中，发育钾化、绿泥石化、硅化、绿帘石化等围岩蚀变。地球化学特征显示流纹斑岩为钙碱性系列，岩石具有高SiO2、富碱、高K2O、高钙铁、低镁、K2O／Na2O值偏高的特点，为强过铝质岩石。w（∑REE）值为76．28×10^-6～222．54×10＆-6（∑LREE／∑HREE）比值较大，为4．08-12．30，属于轻稀土元素富集型。成矿流纹斑岩形成于1372=2．1Ma（SHRIMP锆石U—Pb法）～138．8±1．4Ma（LA-MC—ICPMS锆石U—Pb法），属早白垩世。铅锌矿属于次火山斑岩脉型铅锌（银铜）成矿系列，划分为次火山斑岩脉型和次火山热液破碎带型两种矿床成因类型。

Genetic relationship between rhyolite porphyries and lead-zinc mineralization in Lizikeng volcanic basin, northern Wuyishan

Lizikeng volcanic basin is located in the east section of the Mesozoic Yuefengshan-Lizikeng volcanic rock belt, northern Wuyishan. The known lead-zinc（copper, sliver） ore-bodies or mineralizations which are shown as veinlet-disseminated and vein ores are mainly occurred in internal or external contact zones and wall rocks of rhyolite porphyries, where wall-rock alterations such as potassic alteration, chloritiza- tion, silicification and epidotization are well developed. The results of geochemical analyses show that the rhyolite porphyries belong to strongly peraluminous calc-alkaline series rocks with high contents of alkali, SiO2,K2O, Ca, Fe, high ratios of K20/Na20 and low contents of Mg, w（EREE）values vary from 76.28×10^-6to 222.54× 10^-6, w（S.LREE/Y.HREE） values are relatively high（4.08-12.30）,suggesting a strongly right-inclined LREE enrichment type. Ore-forming rhyolite poyphyries are occurred in 137 4-2.1 Ma （SHRIMP zircon U-Pb）-138.8±1.4 Ma（LA-MC-ICPMS zircon U-Pb）, belong to the Early Cretaceous. The lead-zinc deposit can be genetically divided into subvolcanic porphyry vein type and subvolcanic hy- drothermal fracture zone type, belonging to subvolcanic porphyry vein type lead-zinc （copper, sliver） metallogenic series.