Order of sphalerite and galena precipitation: A case study from lead-zinc deposits in southwest China  

闪锌矿和方铅矿的沉淀顺序：以中国西南铅锌矿床为例（英文）

作　　者：ZHANG Yan HAN Run-sheng WEI Ping-tang 张艳;韩润生;魏平堂(Kunming University of Science and Technology,Southwest of Geological Survey,Geological Survey Center for Non-ferrous Mineral Resources,Kunming 650093,China;Kunming Geological Prospecting Institute,China Metallurgical Geological Bureau,Kunming 650024,China)

机构地区：[1]Kunming University of Science and Technology,Southwest of Geological Survey,Geological Survey Center for Non-ferrous Mineral Resources,Kunming 650093,China [2]Kunming Geological Prospecting Institute,China Metallurgical Geological Bureau,Kunming 650024,China

出　　处：《Journal of Central South University》2020年第1期288-310,共23页中南大学学报（英文版）

基　　金：Projects(41572060,41802089,U1133602)supported by the National Natural Science Foundation of China;Project(2017M610614)supported by the Postdoctoral Science Foundation,China;Projects(2008,2012)supported by the YM Lab [2011] and Innovation Team of Yunnan Province and KMUST,China

摘　　要：Most of the lead and zinc deposits in Southwest China, are characterized by mineral zoning, which is especially true for the Huize and Zhaotong deposits. The mineral assemblage zoning is consistent for both horizontal and vertical zoning, from the base(center) of the ore body to the top(outermost), the mineral zones are as follows. I-1: coarse-grained pyrite and a little puce sphalerite;I-2: brown sphalerite, galena, and ferro-dolomite;I-3: galena, sandy beige and pale yellow sphalerite, and calcite;and I-4: fine-grained pyrite, dolomite, and calcite. Among them, sphalerite is the landmark mineral of different zoning. From I-1 to I-3, the color of sphalerite changes from dark to light, its crystalline size changes from coarse to fine, and its structure changes from disseminated to veinlet. This mineral zoning is seen not only on a microscopic scale, but is also clear on a mesoscopic and macroscopic scale. It is caused by the order of the sphalerite and galena precipitation. We studied the metallic minerals and fluid inclusions using a thermodynamic phase diagram method, such as lgfO2–lgfS2, pH–lgfO2, pH–lg[Pb^2+] and pH–lg[HS^-], discussed the constraints on the order of the sphalerite and galena precipitation in the migration and precipitation process of lead and zinc under different pH values, oxygen fugacity, sulfur fugacity, and ionic activity. We also explain the formation mechanism and propose that the main controlling factor of the order of the sphalerite and galena precipitation is sulfur fugacity.中国西南的大部分铅锌矿床具有明显的矿物组合分带特征,尤其是会泽和昭通铅锌矿床。矿物组合分带具有垂向分带和水平分带,即从矿体底部(中心)到顶部(外围)具有如下矿物分带:I-1:粗晶黄铁矿+少量深色闪锌矿;I-2:棕色闪锌矿+方铅矿+铁白云石;I-3:方铅矿+浅褐色和黄色闪锌矿+方解石;I-4:细晶黄铁矿+白云石+方解石。其中,闪锌矿是不同分带的标志性矿物。从I-1到I-3,闪锌矿颜色从深变浅,晶粒从粗晶变为细晶,结构从浸染状变为细脉状。这种矿物分带现象不仅在微观尺度可以观察到,在宏观尺度上也同样存在。它是由闪锌矿和方铅矿的沉淀顺序引起的。本文在研究金属矿物和流体包裹体的基础上绘制了几类热力学相图,如lgfO2–lgfS2,pH–lgfO2,pH–lg[Pb^2+]和pH–lg[HS^-],讨论了不同pH,氧逸度,硫逸度和离子活度条件下铅锌运移沉淀过程中闪锌矿和方铅矿沉淀顺序的制约条件,解释了矿物组合分带的形成机制,认为闪锌矿和方铅矿沉淀顺序的核心控制条件是硫逸度。

关 键 词：precipitation order thermodynamic phase diagram mineral zoning lead and zinc deposit southwest of China 

分 类 号：P618.42[天文地球—矿床学] P618.43[天文地球—地质学]