Geochemical Characteristics Of The Diaoquan Ag-Cu Deposit And Their Constrains On Genesis Of The Deposit In Lingqiu,Shanxi Province

This thesis researched on geochemical characteristics (major elements, trace elements, REE and isotopes), and on petrologic and geochemical characteristics of biotite quartz monzonite, granite porphyry, skarn and marble in Diaoquan Ag-Cu deposit. The ore-forming material source and ore genesis are studied in view of geochemistry, based on the lead isotope analysis of deferent rocks and ores and on the sulfur and lead isotope tests of various pyrites. Single-zircon U-Pb age of biotite quartz monzonite and granite porphyry and Re-Os age of molybdenite are studied. The main work and achievement of this dissertation are as follows:(1)The geochemical characteristics of mineralization elements in biotite quartz monzonite, granite porphyry,skarn and marble show that the magmatic rock mass may be the carrier of Ag,W and Mo.The geochemical characteristics of major elements show that biotite quartz monzonite is quasi-aluminous alkaline A-type granite,belonging to intermediate rock, and that granite porphyry is aluminous alkaline A-type granite, belonging to acid rock. The differentiation index (DI) of the mass shows that the differential degree of granite porphyry is high than that of biotite granite.On the trace element aspect, biotite quartz monzonite and granite porphyry both enrich high field strength elements Ti and Y, and lithophile element Rb, depleted in high field strength elements Zr and Hf, and lithophile element Sr. The enrichment degree of Rb is the highest, Nb/U decreases with the increase of MgO content, and Ba/Nb ranges widely, which show that the rocks have been contaminated by crust.The REE chondrite standard distribution map of biotite quartz monzonite and granite porphyry presents LREE enrichment and HREE deficit, which shows that the two kinds of rock mass have homology. The distribution curve of granite porphyry is more dispersed than that of biotite quartz monzonite, with relatively low similarity, and the LREE fractionation level and δ Eu value granite porphyry are greater than that of biotite quartz monzonite, which shows that fractionation level of granite porphyry is greater than biotite quartz monzonite, with more crust material sources.The geochemical characteristics of trace elements and REE in rock, skarn and marble show that the mineralization has been influenced by magmatism of biotite quartz monzonite, and granite porphyry, therefore, it doesn’t have obvious inherit evolution relationship with marble.(2)The diagenetic ages of biotite quartz monzonite and granite porphyry are (163.7±1.8)Ma and (154.5±1.1)Ma, about Jurassicperiod, based on single grain zircon U-Pbage-measurement method. And the forming age of deposit is about (132.3±6.1)Ma based on the Re-Os isotopes age-measurement method. The time between diagenesis and mineralization is about22Ma.The Pb elements in the ore and skarn granite are the crust mantle material mixed ones originated from fractionation progress based on the Pb isotopic analysis, while the Pb in marble comes from upper crust, with addition of orogenic belt lead. Pyrites in layered pyrite mass and skarn type magnetite mass have the same material source.The S sources in ores in the area have the character of uniformity based on the S isotopic analysis. Pyrites in layered pyrite mass and skarn type magnetite mass have the same S source, displaying the character of magmatic sulfur.(3)Based on the analysis of geological and geochemical characteristics of the deposit, It is suggested that yanshanian magmatic rock is mineralization mother rock, metallogenic material comes mainly from the magma.