摘要
会泽型铅锌矿床是川-滇-黔接壤区广泛分布的直接受冲断褶皱构造控制的铅锌矿床,其突出特点之一是矿体中矿物组合具有明显的分带性,其形成机理研究是探究构造驱动成矿流体演化过程的关键科学问题之一。本文通过精细解剖典型的云南昭通铅锌矿床,以岩矿鉴定和矿物流体包裹体研究为基础,建立了相关热液体系中多组分平衡关系,构建了铅、锌、铁及其氧化物和硫化物的logfo2-logfs2相图。根据计算结果和相图讨论了形成不同矿物及其组合的流体迁移、沉淀的氧硫逸度条件和金属矿物分带机理。以473 K相图为例,解析了16种矿物及其组合稳定存在的logfo2、logfs2范围及特征,揭示了氧-硫逸度是铅锌元素共生分异的主要原因,并直接控制了矿物组合分带。研究表明,随着成矿流体的演化,温度下降,矿物沉淀所需的fo2、fs2随之减小,氧化还原作用趋弱。理论计算和相图与宏观、微观地质事实相符。
The Huize-type Pb-Zn deposits in Northeast Yunnan, located in the north side of the Sichuan- Yunnan-Guizhou lead-zinc polymetallic mineralization domain and tectonically on the southwestern margin of the Yangtze block, are controlled by thrust-fold structures directly. The Zhaotong large-size Pb-Zn deposit is one of the representatives of these deposits. The major minerals of the Huize-type lead-zinc deposits are commonly characterized by zonation, i.e., coarse-grained pyrite＋a little puce sphalerite→brown sphalerite＋galena＋ferrodolomite→galena＋sandy beige and faint yellow sphalerite＋quartz＋calcite→ fine-grained pyrite＋dolomite＋calcite from the floor to the roof of the ore bodies. The ore-forming mechanism of the pattern is one of the key scientific issues in the study of the evolution process of the ore-forming fluid driven by structure. This paper, demonstrating the Zhaotong Pb-Zn deposit as a case study, has studied the controlling mechanism of oxygen-sulfur fugacity for the main metal sulfide assemblages and mineral zoning. It will contribute to understand the forming mechanism of paragenesis and separation of lead and zinc. logfo2-logfs2 phase diagrams for the lead, zinc, iron sulfides and oxides under equilibrium in the relevant hydrothermal system have been re-constructed on the basis of the test results of fluid inclusions and the results of rock and ore appraisal. The calculated results and the phase diagrams indicated that thefo2andfs2 conditions of the transport and precipitation in which the various kinds of minerals and their assemblages formed, and the processes and mechanism of the metallic mineral zoning have been discussed. Taking the 473 K phase diagram as example, the stable logfo2-logfs2 ranges of the 16 kinds of minerals and their assemblages and the block distribution are analyzed. It is shown that metallic mineral zoning and the lead-zinc paragenesis and separation of the deposit was resulted from the variation of fo2andfs2. With the decrease of the temperature, the values offo2andfs2required for mineral precipitation also decreased. The results of the theoretic calculation and the phase diagrams are consistent with both macro-geological and micro-geological characteristics of the lead-zinc mineralization.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2014年第4期898-907,共10页
Geotectonica et Metallogenia
基金
国家自然科学基金项目(批准号:U1133602
40863002
41103026)
云南省自然科学基金重点项目(编号:2010CC005)
国家危机矿山矿床成矿规律研究专项(编号:20089943)
云南省矿产资源预测与评价重点工程实验室(2012)和云南省昆明理工大学创新团队项目资助
