Pyrite In Situ Geochemical Characteristics

Pyrite is the most common mineral in sulfide deposit,and has abundant metallogenic information.In recent years,pyrite in-situ geochemical researches used in laser ablation inductively coupled plasma mass spectrometry(LA-ICPMS)technique have been received much important scientific information,and provide relevant evidence for genesis of mineral deposit.Tongling ore cluster region is one of the few large-scale Cu-Au deposit concentration areas.There are multiple and typical deposits types,and are in the spotlight bedded sulfide ore deposits.Due to its specificality,its genesis of the bedded sulfide ore deposits has been a subject of much debate.In this study,x-ray diffraction(XRD),electron probe microscope(EPMA),LA-ICPMS and S isotope of different type's pyrite were systematically investigated in Xinqiao and Taoyuan layered sulfide ore deposits,respectively.Combining previous research results,we obtain the main conclusions as follow:1.The measurement results of EMPA show that Fe and S contents of the different type's pyrite fromXinqiao and Taoyuan deposits have no obvious difference.All of them are the sulfur-richened pyrite.Its S/Fe atomic ratio,?Fe and ?S values,w(Fe)and w(S),w(Fe)/w(S)values reflect obvious characteristics of sedimentary pyrite.2.The LA-ICP-MS trace element determination results showed that in situ trace element concentrations of the different type's pyrite from Xinqiao and Taoyuan deposits have no obvious differences too,just slightly higher As,Au,Ag,Pb and Zn values of the pyrite in Taoyuan deposit.However,all types of pyrite have the characteristics of low Co,Ni,Se contents and high As content.Co/Ni,S/Se,w(Zn)/[w(Zn)+w(Pb)],(Cu+Zn+Pb)/(Co+Ni)values,and Co-Ni diagram,Co-Ni-As diagram features indicate that the pyrites of the two deposits are not a single origin,but are more likely to be compound origin.The Xinqiao and Taoyuan depsoits were likely formed from combined action of the late Paleozoic Hercynian hydrothermal sedimentation and Mesozoic Yanshan period magmatic hydrothermal activities.3.The S isotope analysis results indicate that the ?34S values of Taoyuan pyrite are relatively high than those of Xinqiao pyrite.S isotopic characteristics of all samples are consistent with the characteristics of deep source sulfur,indicating that the sulfur of the two deposits is derived from deep source magma sulfur.4.Comprehensive analysis consider that the pyrite of Xinqiao deposit is mainly originated from magmatic hydrothermal,certainly affected by the early hydrothermal sedimentation.The Taoyuan deposit may be undergone two processes of Hercynian hydrothermal sedimentary and Yanshan magmatic hydrothermal superimposition,and be superimposed and reformed genesis.