The Geochemical Characteristics Of Fozichong Pb-Zn Ore Field, Guangxi

Fozichong Pb-Zn deposit,located in the southwest of Qinhang belt and the northeast of Bobai-cenxi deep fracture,is a mineralization favorable zone, where the geological evolution is very complex. The Pb-Zn orebodies are mainly produced in the limestone sandwich of the ordovician and the lower silurian series, controled by the NNE-striking and NE-striking faults.On the basis of predecessors’ research achievements, the research in this paper is mainly focused on the characteristics of fluid inclusions in defferent levels different mines and the characteristics of rare earth elements in defferent rock masses and ore bodis, the understandings we obtained are as follows:(1) The rare earth elements of Guangping rock mass、Dachong Granite diorite rock mass、granite porphyry, and dacite porphyry show that,the8Eu of Guangping rock mass is0.16,have a strong europium negative anomaly,on the distribution pattern figure of rare earth elements appears to be shelving to the right of "V" type, Significantly different from granodiorite porphyry, granite porphyry and dacite porphyry. Granodiorite porphyry, granite porphyry and dacite porphyry in addition to total rare earth is different,the curve shape is consistent, the distribution patterns of rare earth elements are closely to a smooth curve,the europium negative anomaly is not obvious, this consistency shows that granodiorite porphyry, granite porphyry and dacite porphyry is cognate magma evolution.(2) On the distribution pattern figure of rare earth elements,the distribution curve of the massive ore and the banded ore is consistent,and closely consistent with the curve of granite porphyry and dacite porphyry.All these show that two types of ore has similarities in material source,and more closely relationship with granite porphyry and dacite porphyry.(3) Fozichong Pb-Zn deposit has three types of fluid inclusions through detailed petrographic observation:gas-liquid two-phase inclusions, pure liquid inclusions and containing mineral three-phase inclusions, gas-liquid two-phase inclusions can be diveded into two forms:rich liquid two-phase inclusions、rich gas two-phase inclusions,the pure liquid inclusions associate appear with other inclusions, is the secondary inclusions for the late groundwater into it,the child mineral is salt crystal,this type inclusions have a few quantity,we just measured four data in a sample. According to the results of Microscopic measurement, the captured temperature of gas-liquid two-phase inclusions, concentrated in160-250℃and300-410℃range,mainly in middle-high temperature, is consistent with sulfur isotope temperature measurement results. ore-forming fluid of Fozichong Pb-Zn Deposit is derived from the mixture of magmatic water and atmospheric precipitation,the characteristics are middle-high temperature and low-middle salinity; By the means of "fluid inclusion assemblage", we can infer that in Fozichong Pb-Zn deposit, there are existing at least two periods ore-forming fluids;Calculate the physicochemical parameters,we concluded that the deposit trapping pressure is31.87～107.20Mpa,the average pressure of62.64Mpa,this shows that Fozichong Pb-Zn deposit has a high pressure,converted into ore-forming buried depth of1.18～3.97km, the average depth of2.32km, the buried depth is deep, As a result, Fozichong is a high temperature、high pressure, hypogene hydrothermal type deposit.