| Paomaping Pb-Zn deposit is located in the northeast of Jinding giant orefield in Lanping basin,northwestern Yunnan,SW China.It was controlled strongly by geological structure,and with the characteristics of various types of mineralization and special ore fabric.This research mainly through detailed geologic survey and 2140m,2180m level tectonic-lithofacies and alteration-mineralization geological observation,using ore petrography,microfabric study,energy spectrum analysis,two secondary ion mass spectrometry analysis,combined with the existing mineral electron probe and sulfur isotope data,the characteristics and temporal and spatial distribution of different types of ores are systematically studied,fine reveals the mineralization process.This research mainly obtains the following understanding:(1)The main lead-zinc ore bodies are columnar,large vein and irregular in the upper Triassic Sanhedong formation(T3s)limestone and breccia limestone,which is located in the lower part of the Paleogene Yunlong formation(E1y).The ore minerals are mainly galena,sphalerite,pyrite,marcasite.The main gangue minerals are calcite,barite,celestite,gypsum etc.Paomaping lead-zinc deposit has certain mineralization-alteration zonation,from early to late has the following mineral assemblages and mineralization sequence:pyrite+marcasite+calcite?sphalerite+pyrite?barite+celestite+gypsum?galena+calcite,showed the characteristics of hydrothermal filling and mineralization.(2)Ore strcture maily includes massived,veined,disseminated,taxitic,banded,brecciated brecciform,and ring structure and so on.ore texture maily includes ring belt,gelatineous(or strawberry),skeleton crysta,corrosion,network and radial texture and so on.Ring,gelatineous(or strawberry)texture and ring structure show the characteristics of multi-stage mixed fluid and mineral fast crystallization.(3)Sphalerite contains a small amount of Ni and Co,and Zn/Cd value ranged from 86.16-547.50,average 310.81.It is mainly in the interval 350-548 and 86-300.It shows that the formation of this deposit has experienced two stages:middle-high temperature and middle-low temperature.The content of As in sphalerite is obviously higher than that of MVT type deposit,but the distribution is regular,but the content of Fe is lower than that of massive sulfide type and skarn type deposit,which is similar to that of MVT type deposit.Pyrite is hydrothermal origin,slightly rich S and deficient Fe,Co ?Ni.(4)The ?34S(VCDT)value of galena is between-23.1‰ and-6.9‰,with an average of-14.9‰?The ?34S(VCDT)value of sphalerite is between-14.6‰ and-12.3‰,with an average of-13.7‰?The 834S(VCDT)value of pyrite is between-35.8‰ and-20.5‰,with an average of-23.2‰??34S(VCDT)values were all negative,which showing enrichment of light sulfur characteristics and biological characteristics of sulfur in ore reduction.The sulfur in the ore-forming fluid is the result of the interaction of biogenic sulfur and heavy sulfur,and the main mechanism of action is the increase of temperature and the thermochemical reduction(TSR)of organic matter.(5)The main ore control factors are affected by structure and lithology,thrust nappe opens a channel for fluid mixing,and metal sulfide precipitation as acid reaction,limestone dissolution is easy to collapse,which is not only conducive to the upper part of the fluid filled,but also can increase the host space. |
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