滇中荒田铅锌矿床Rb-Sr同位素年代学与C-O-S-Pb同位素地球化学特征

Rb-Sr isotopic geochronology and C-O-S-Pb isotope geochemical characteristics of the Huangtian Pb-Zn deposit, Central Yunnan

滇中荒田铅锌矿床赋存于下二叠统碳酸盐岩与上二叠统峨眉山玄武岩接触界面上,矿体主要呈似层状、透镜状产出。矿石矿物组合以闪锌矿、方铅矿为主,脉石矿物以石英、方解石、白云石为主。热液方解石C、O同位素组成表明荒田铅锌矿床成矿流体中CO_2的碳具有多元性,主要来源于幔源与海相碳酸盐岩的混合碳;硫化物硫同位素组成表明荒田铅锌矿床硫以岩浆硫为主,可能混有其他硫源(可能包括地层硫酸盐),铅同位素表明赋矿围岩、玄武岩和燕山期花岗岩均有可能为成矿提供了成矿物质,是多源混合后的产物;闪锌矿Rb-Sr同位素等时线年龄为(83.2±3.4)Ma,指示荒田铅锌矿床形成于晚燕山期,荒田铅锌矿床成矿动力学背景可能与右江褶皱带在中生代末期发生了大规模的岩石圈伸展有关。而晚二叠世海相喷发火山岩对矿区铅锌矿床的形成起了重要的盖层、赋矿层及矿化作用。综上,荒田铅锌矿床成矿流体中的不同组分来源不同,矿床类型为沉积-改造型矿床。

The Huangtian Pb-Zn deposit occurs along the contact zone between the carbonate rocks of lower Permian and Emeishan basalt of upper Permian. Orebodies are mainly bedded and lenticular in form. The ore minerals are mainly sphalerite and galena,whereas the gangue minerals are quartz, calcite and dolomite primarily. The composition of C and O isotopes of the hydrothermal calcite indicates that the carbon of CO2 in the ore-forming fluid is pluralistic, mainly from the mixed carbon of the mantle source and the marine carbonate rocks. The sulfur isotope composition of sulfide indicates that the sulfur in the lead-zinc deposit isdominated by magmatic sulfur and may be mixed with other sulfur sources（possibly including formation sulfate）. The lead isotopes indicate that the metallogenic material mainly came from the surrounding rock. The lead isotopes indicate that the metallogenic material mainly came from the surrounding rock, basalt and Yanshanian granite, which is the product of multisource mixing.Isochron age of Rb-Sr isotope is（83.2±3.4） Ma, indicating the formation of the lead-zinc deposit in the late Yanshanian period. The metallogenic dynamic background of the Huangtian Pb-Zn deposit might have been related to the large-scale lithospheric extension of the Youjiang fold belt at the end of Mesozoic. The Late Permian marine eruption volcanic rocks played an important role in the formation of lead and zinc deposits in the aspect of cover and ore-bearing layer and mineralization. All the geochemical information suggests that the source of ore-forming metals and fluids of the Huangtian Pb-Zn deposit was mixed product. The type of the deposit is sedimentary and reformed deposit.