复杂成矿系统中热液锆石的成因、定年及其对流体演化的启示：以湘南多金属矿集区为例

The southern Hunan ore concentration area can be recognized as a complex metallogenic system. The composition, property and evolutionary processes of ore-forming fluids, the multi-element mineralization sequences, and the mineral precipitation environment and mechanism are important contents for understanding the origin of this metallogenic province. Though lots of petrological, geochemical and geochronological research has been done in this area, the detailed multi-stage mineralization processes are still rarely known in the specified deposits of this complex metallogenic system. Thus, the elaborate characterization of the metallogenic processes is expected to be made by using geochemical and geochronological microzone analysis for typical hydrothermal minerals. This study attempts to investigate the hydrothermal zircons of the typical magmatic-hydrothermal deposits in this area, carry out zircon typological and crystal population and other physical property study, observe the internal structure and Raman spectra characteristics, identify the composition and genesis of fluid and mineral inclusions in zircons, and precisely determine the U-Pb age, trace element and O, Hf isotopic composition of hydrothermal zircons. Based on these analyses, this study aims to summarize the features and differentiating methods of hydrothermal zircons in southern Hunan polymetallic ore district, prove the exists of hydrothermal zircons and classify them in typical medium-high temperature magmatic-hydrothermal deposits, and reveal the genetic mechanism of different zircon typological and crystal populations and their connections to multi-element mineralization sequences and metallogenic stages. Using the implicit geochemical information hosted by hydrothermal zircons, the origin and evolution of multi-stage metallogenic fluids can be determined, and the precipitation mechanism and metallogenic model of different metal elements can be also fixed. Based on the common Pb correction and radioactive Pb loss estimation, this study offers high precision U-Pb dating to constrain the multi-stage mineralization in southern Hunan ore concentration area during early Yanshanian period.

湘南多金属矿集区是一个复杂成矿系统，其成矿流体组成、性质及演化过程、多元素矿化时序及矿质沉淀环境和机制是深入理解其成因的重要内容。本研究拟以湘南矿集区典型岩浆热液矿床的热液锆石为研究对象，进行锆石群型及晶形等物理特性的研究，观测锆石内部结构及拉曼光谱特征，查明锆石中流体和矿物包裹体的组成和成因，准确测定热液锆石的U-Pb年龄、微量元素及O、Hf同位素组成。在此基础上，总结湘南多金属矿集区热液锆石的鉴别特征和方法，对典型中-高温岩浆热液矿床中热液锆石的存在进行证明、鉴别及分类，探明不同晶型、群型热液锆石的成因机理及其与成矿矿种、成矿期次之间的关系。利用热液锆石所含隐含的地球化学信息揭示多期次成矿流体的起源与演变，建立不同金属矿种矿质的沉淀与成矿模型。在普通铅校正及放射性铅丢失估算的基础上对热液锆石进行高精度的U-Pb定年，为燕山早期湘南多金属矿集区多期次成矿作用提供可靠的年龄制约。

南岭中段湘南多金属矿集区是一个复杂成矿系统，其成矿流体组成、性质及演化过程、多元素矿化时序及矿质沉淀环境和机制是深入理解其成因的重要内容。本研究以湘南矿集区两个典型岩浆热液矿床—香花岭和柿竹园多金属矿床的多类型锆石（包括热液锆石）为研究对象，进行了锆石群型及晶形等物理特性的研究，观测了锆石内部结构，查明了锆石中矿物包裹体的组成和成因，准确测定了热液锆石的U-Pb年龄、微量元素及Hf同位素组成。在此基础上，总结了湘南多金属矿集区热液锆石的鉴别特征和方法，对典型中-高温岩浆热液矿床中热液锆石的存在进行了证明、鉴别及分类，探明了不同晶型、群型热液锆石的成因机理及其与成矿矿种、成矿期次之间的关系。利用热液锆石所含隐含的地球化学信息揭示了多期次成矿流体的起源与演变，为燕山早期湘南多金属矿集区多期次成矿作用提供了可靠的年龄制约。.通过对与香花岭多金属矿床相关的癞子岭岩体和矽卡岩、硫化物矿石内多期次及多类型锆石的研究，指出香花岭锡多金属矿床经历了多阶段成矿作用：志留纪—三叠纪锡初始富集阶段（~420和~220 Ma），侏罗纪锡成矿阶段（~150 Ma），侏罗纪附属铅锌成矿阶段（150 Ma后）和白垩纪热液叠加阶段（~80Ma）。通过对柿竹园多金属矿床流体蚀变热液锆石的地球化学和形态特征的研究，区分了三种类型的热液流体：I型流体富含大部分元素（如Zr、Hf、U、Th、P、REE、Ti、Nb、Ta、Al、Ca）和成矿元素（如W、Sn），温度、压力较低，还原性较强，可能是主要成矿流体；II型流体具有微量元素含量低（含成矿元素）和相对较高的温度、压力和氧逸度的特点；III型流体是从II型流体演化而来的，为其他两种类型的过渡流体。根据锆石地球化学和形态特征，建立了千里山岩体中锆石的岩浆热液演化模型以及柿竹园超大型矿床形成过程的成矿模式。