| Maoping Pb-Zn mining area is located in the northeastern Yunnan Pb-Zn metallogenic belt,where in the south-central part of Sichuan-Yunnan-Guizhou Pb-Zn metallogenic area.It is situated in the composite parts of Xiaojiang fault,Zhaotong-Qujing hidden fault and Ziyun-Yadu fault.Up to now,more than ten Pb-Zn deposits?points?have been found in this area,such as Maoping,Fangmaba and Luozehe,and each deposit is obviously controlled by the NE-trending compression-torsion fault and distributed along the north-east direction.Maoping Pb-Zn deposit is the main research object in this paper,and the characteristics of ore body,geochemical characteristics of the deposit and ore-controlling factors are studied.It can be seen that the Maoping Pb-Zn deposit is mainly produced in the limestone and dolomite strata of the Upper Devonian and Middle Carboniferous.The main ore-forming structures are NE-trending Maomaoshan inversion anticline and the main ore-controlling structures are NE and NW-trending faults.The main orebodies are layered and layered,and the occurrence of flat columnar,columnar,cystic and irregular orebodies can also be seen.They extend along NEE-SWW direction,with a dip angle of 60°80°,and the tendency to extend deeper than toward the extension.The structure of the ore mainly includes granular-semi-automorphic granular structure,mosaic structure,crushed structure,and residual structure.The ore structure mainly consists of massive structure,disseminated structure,net vein structure,strip structure,and spot shape.Structure,stratified structure,veins and dissolved porous structures.According to the ore characteristics,the metallogenic stages can be divided into three stages:sedimentary-diagenetic stage,hydrothermal stage and supergene stage.And the surrounding rock alteration is relatively simple,it is mainly composed of dolomitization,pyrolysis,pyrite mineralization and silicification.Geochemical characteristics of the deposit indicate that CaO?28.23%30.87%?and MgO 19.59%21.72%)are the main ore-bearing dolomites,with a small amount of SiO2.The?REE is low(average 6.33×10-6),and the values of?Ce and?Eu are all<0.95,showing a medium negative anomaly.And the Sr/Ba value?9.6715.61?is greater than 1,the Sr/Cu value?11.9940.13?is greater than 5.0,and the Cu/Zn value is much less than 0.21,which shows that the paleosedimentary environment in this area is marine environment under the condition of drought reduction.The average?REE content of ores is 2.32×10-6,LREE/HREE is 2.158.31?average 4.63?,and LaN/YbN is 3.7314.49?average 7.87?,showing the right-dip REE distribution pattern.The?Ce is 0.620.92?average 0.80?,showing a moderate negative anomaly,and the?Eu is 2.583.02?average 2.93?,showing a strong positive anomaly,which may be caused by the transformation of ore through the reducing environment.The study of H-O isotope shows that the ore-forming fluid of Maoping Pb-Zn deposit has the characteristics of"multi-source",and the inclusion composition of gangue minerals in the ore area may be closer to the characteristics of ore-forming fluid in the ore-forming period.The uniform temperature of two-phase gas-liquid water inclusions in dolomite and calcite is mainly concentrated between 90°C and180°C,and the salinity change is 0.1820.52wt%,which indicates that the ore-forming fluids are of medium-low temperature,medium-low salinity.In this paper,zircon is first selected from ore and U-Pb isotope dating is carried out.It is fully confirmed that the ore-forming material of the deposit is provided by ore-bearing rock series and underlying strata.The study of ore-controlling factors shows that the Maoping Pb-Zn deposit is mainly controlled by strata,lithology,palaeogeographic environment and structure,among which structural factors are the main factors.Further study suggests that NE-SW structure in the mining area may be ore-guiding and ore-controlling structure,while NW-SE trending structure may be the late ore-breaking structure.Combined with the research results of this paper and the predecessors,it is considered that the ore-forming fluid of the deposit has the characteristics of“multi-source”.The C in the ore-forming hydrothermal fluid is mainly from marine carbonate rocks,and it is not excluded that magma may be added in the later stage;The variation range of?34S is 7.96‰24.10‰,and it has the characteristics of?34Spyrite>?34Ssphalerite>?34Sgalena.It is considered that sulfur is the mixed sulfur after the mixture of lanthanum sulfur and seawater sulphur;The Pb isotope composition characteristic analysis showed that the source region?value was between 9.07 and9.81,it is considered that the Pb is a mixture of mantle-derived and oceanic crust lead.Compared with the MVT-type Pb-Zn deposit and the adjacent Huize Pb-Zn deposit in Yunnan,the Maoping Pb-Zn deposit is considered to be a“structur-fluid-penetration”?HZT-type?Pb-Zn deposit.Based on the geological and geochemical characteristics and ore-controlling factors of the deposit,the metallogenic model of Maoping Pb-Zn deposit has been preliminarily established. |
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