滇西芦子园铅锌矿床构造-流体与成矿关系研究

Luziyuan Lead-Zinc deposit in western of Yunnan province, southwest China is located in the Zhengkang ore district, Baoshan-Zhengkang Lead-Zinc poly-metallic ore zone in the southern "Sanjiang" metallogenic belt. It is a super-large Pb-Zn-Fe-Cu poly-metallic deposit prospected in recent years. The ore body was produced in the carbonate rocks of the Shahechang formation in upper Cambrian, and it is a skarn-type Pb-Zn deposit obviously controlled by the structure. Some research works has been done by predecessors and a certain results have been achieved. However, the studies on mineralization-alteration zoning, metallogenetic elements(i.e. Pb, Zn, Fe, Cu) zoning, spatial zoning of the deposit have never been involved, and the studies concerning ore-forming fluids, source of ore-forming substances and metallogentic regulations are relatively deficient. Due to the recognition on the geneses and mineralization of the deposit remains inconclusive, it is difficult to guide the forecast and evaluation work of the deep and peripheral ore prospecting. For this reason, the application is proposed to explore the coupled relations between the structure, metallogentic fluid and metallogenesis to reveal the metallogenetic mechanism and to create a practical metallogentic pattern by the staging and matching of the metallogenetic structures of the mineralization area, in connection with the systematic geochemistry analysis and experiment data of the mineralization area, based on the mineralization-alteration zoning, metallogenetic element zoning, spatial zoning for the ore bodies with different metallogenetic types, tectonites, skarns and alteration rocks in different locations. This research work is not only significant for the abundance of metallogenetic theory for the Lead-Zinc deposit, but also has an important guidance for the ore-prospecting forecast in the deep and pheripheral area of the mineral area.

滇西芦子园铅锌矿床位于"三江"成矿带南段保山－镇康铅锌多金属成矿带镇康矿集区内，是近年来经勘查发现的超大型铅锌铁铜多金属矿床。矿体产于上寒武统沙河厂组碳酸盐岩中，是明显受构造控制的矽卡岩型铅锌矿床。前人对该矿床的研究工作也取得了一些研究成果。然而，对本区矿化蚀变分带、成矿元素分带（Pb、Zn、Fe、Cu）及矿床的空间分带研究还未有涉及，有关成矿流体、成矿物质来源及成矿规律的研究仍较薄弱，因而，对矿床成因及成矿作用的认识至今尚无定论，难以有效指导矿区深边部及其外围的找矿预测评价工作。本申请拟以该矿床不同矿化类型矿体、不同部位构造岩、矽卡岩及蚀变岩为研究对象，对矿化蚀变分带、成矿元素分带和矿床空间分带的基础上，通过对矿区成矿构造的分期配套，结合系统的矿床地球化学分析测试资料，从成矿物质来源和成矿流体来源，探讨构造-成矿流体-成矿作用之间的耦合关系以揭示矿床成矿机理，建立切合实际的成矿模式。

滇西保山地块是我国西南三江成矿带中重要的Fe-Cu-Pb-Zn-Ag-W-Sn及稀有金属富集区，区内已发现中、大型Pb-Zn多金属矿床5个以及数十处矿（化）点。其中，芦子园超大型Pb-Zn-Fe（Cu）多金属矿床（Zn+Pb金属量＞4.2Mt、Fe矿石量达301Mt）是保山地块上系列同类矿床的典型代表，矿体呈似层状顺层产出，含矿围岩以矽卡岩为主，但矿床内至今未发现与矿床成因有联系的岩体，因而已有研究对矿床成因的认识一直众说纷纭。本基金课题针对芦子园Pb-Zn-Fe（Cu）多金属矿床有关成因争议较大的研究现状，通过对矿床矿化时空结构、构造期次划分、流体包裹体以及矿床地球化学的系统研究，探讨了矿区构造-成矿流体与成矿作用之间的耦合关系，以解决矿床成矿物质、成矿流体来源和成矿机理等科学问题，主要取得了如下认识和成果：.（1）构造序次分析表明，矿区内发育NE、SW、近SN和近EW四组不同方向的构造行迹组合，显示出多期次的构造活动性。其中，NE向断裂组控制了整个矿床矿体的规模、形态以及在平面和空间上的展布规律，是区内最重要的导矿、容矿构造。.（2）矿床蚀变矿化分带研究表明，上部大理岩型Pb-Zn（Ag）→中部大理岩-矽卡岩型Pb-Zn-Cu（Fe）→下部矽卡岩型Fe-Cu，具有明显的热液成矿特点，符合典型远程矽卡岩矿床的地质特征。.（3）矿床的形成过程经历了2期5个阶段，通过对各阶段系统的流体包裹体研究表明，初始成矿流体具有中高温、中高盐度、富水、富CO2的浆控特征，而成矿流体到晚阶段比早阶段更具还原性，更有利于硫化物的沉淀。.（4）通过对不同成矿阶段矿物的微量、稀土元素及主成矿阶段矿物的多元同位素研究表明，该矿床成矿流体和成矿物质来源与深源岩浆活动直接相关。.（5）本次获得的矿床成矿期方解石Sm-Nd同位素等时线年龄为130±15 Ma，表明成矿作用发生于早白垩世，响应于中特提斯主洋俯冲-闭合后的陆陆碰撞造山作用，成矿作用发生于增厚地壳伸展减压的动力学背景，是保山地块内部能量强烈聚集地段产生的远程效应。