Occurrence Of Germanium And Element Alternative Mechanism In Sphalerite From Huize Pb-Zn Deposit

Huize Pb-Zn Deposit is located in the southwestern margin of the Yangtze Block and is one of the important germanium-bearing lead-zinc deposits in China.Its reserves of Ge are 517 tons,which reaches to large scale.Altough many research work on the occurrence and replacement mechanism of Ge in Pb-Zn Ore Deposit has been done,there are still controversies.In this paper,we have done detailed field investigation and observation under microscope.Moreover,main micro-analysis and micro-morphology observation of different minerals in the deposit were studied by EMPA,ICP-MS,LA-ICP-MS,FE-SEM,MAPPING methods.The main results and conclusions we got are as follows.1.Combining field investigation and observation under microscope,the formation of the deposit can be divided into three periods and five stages.Periods contain the diagenetic period,the internal mineralization period and the surface oxidation period.The internal mineralization period can be divided into three stages,namely sphalerite-pyrite-calcite stage,sphalerite-galena-pyrite stage and pyrite-calcite stage.2.According to the field interpenetration relationship,hand specimens and microscopic observation,the sphalerite can be divided into three generations(Spl,Sp2,Sp3).Spl is mainly massive,breccia-like fine black(deep)brown sphalerite.Sp2 is mainly vein-like,massive brown(light brown)medium sphalerite,and Sp3 is characterized by vein-like,agglomerate and porphyrit red-brown coarse sphalerite.3.The result of main trace elements of minerals based on EPMA,ICP-MS and LA-ICP-MS analysis indicates that the sphalerite in the deposit is Ge-rich mineral and Ge content in galena,pyrite,calcite and dolomite is below crust element abundance value of Ge,of which some are lower than the detection limit.4.The morphology of the mineral micro-domains was observed by FE-SEM and MAPPING analysis and it is believed that Ge in the sphalerite mainly exists in the form of isomorphism.At the same time,the statistical analysis of Ge content in different types of sphalerites reveals that the Ge elements are spatially disorderly distributed,that is,there is no obvious change in the content of Ge in sphalerite produced in different spatial locations.The enrichment law is obvious in time.Ge is the most enriched in Sp3,sub-enriched in Sp1,and the lowest enriched in Sp2.5.Observing and analyzing the results of LA-ICP-MS,it is found that Ge-Cu exhibits excellent linear positive correlation,Ge-Zn and Ge-Hg show weak correlation.Based on this finding,it is inferred that there are alternative relationships in the mineral crystallization such as 2Cu++Ge2+(?)2Zn2+,Hg2++Ge2+(?)2Zn2+,Ge2+(?)Zn2+.6.The content of Fe and the ratios of Ga/Ge,Ga/In,Zn/Cd in the sphalerite of Huize lead-zinc mine indicate that the deposit is formed in a medium-low temperature environment.Combining the result with elements geochemical characteristics such as In-Ge and Ln(Ga/In),it is further confirmed that the deposit belongs to the medium-low temperature MVT deposits associated with basin fluids.