广西佛子冲铅锌多金属矿田花岗岩特征及成矿时代

Characteristics and Metallogenic Epoch of Monzonitic Granite Porphyry in the Fozichong Lead-Zinc Polymetallic Ore Field, Guangxi

摘要: 广西佛子冲铅锌多金属矿田是华南地区重要的铅锌多金属矿床之一，矿田内广泛发育多期花岗岩，其形成时代与时序关系对限定成矿背景和成矿时代具有重要意义。文章在系统整理佛子冲矿田已有LA-ICP-MS锆石U-Pb年代学数据的基础上，对矿田内不同类型花岗岩的形成时代进行综合对比，并结合典型矿床的空间展布及矿体–围岩关系，探讨花岗岩对铅锌成矿的年代学约束。结果表明，矿田内花岗岩可划分为三期：早三叠世大冲花岗闪长岩(258.2 ± 3.2 Ma)、中侏罗世广平花岗岩(170 ± 6 Ma)及早白垩世晚期古益二长花岗斑岩(105.1 ± 1.7 Ma)，显示出明确的时序分带特征。龙湾、河三矿床为矽卡岩型铅锌矿床，矿体赋存位置及蚀变特征指示其主要成矿作用受早白垩世晚期二长花岗斑岩控制。古益矿床其成矿过程晚于大冲花岗闪长岩侵位，成矿地质体同样与二长花岗斑岩密切相关。佛子冲矿田铅锌成矿主要发生于105 Ma。系统梳理了花岗岩锆石U-Pb年龄数据，为构建佛子冲矿田统一的花岗岩年代学框架及成矿时代限定提供了重要依据。

Abstract: The Fozichong Pb-Zn polymetallic ore field in Guangxi is one of the most important Pb-Zn metallogenic districts in South China. Multiple phases of granitoids are widely developed in the ore field, and their emplacement ages and temporal relationships are of fundamental significance for constraining the metallogenic setting and timing of mineralization. Based on a systematic compilation of previously published LA-ICP-MS zircon U-Pb geochronological data, this study compares the emplacement ages of different types of granitoids in the Fozichong ore field and, in combination with the spatial distribution of representative deposits and the relationships between ore bodies and host rocks, evaluates the chronological constraints of granitoids on Pb-Zn mineralization. The results indicate that the granitoids in the ore field can be divided into three stages: Early Triassic Dachong granodiorite (258.2 ± 3.2 Ma), Middle Jurassic Guangping granite (170 ± 6 Ma), and Late Cretaceous Guyi monzogranite porphyry (105.1 ± 1.7 Ma), showing a well-defined temporal sequence. The Longwan and Hesan deposits are skarn-type Pb-Zn deposits, and the occurrence of ore bodies and alteration characteristics indicate that the main mineralization was controlled by the Late Cretaceous monzogranite porphyry. The mineralization of the Guyi deposit postdated the emplacement of the Dachong granodiorite and is likewise closely related to the monzogranite porphyry. Pb-Zn mineralization in the Fozichong ore field mainly occurred at ~105 Ma. The systematic synthesis of zircon U-Pb ages of granitoids provides an important basis for establishing a unified granitoid geochronological framework and constraining the timing of mineralization in the ore field.