摘要:
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。
Abstract:
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.
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