Geological Characteristics And Genesis Of The Jinxi Copper-molybdenum Deposit In Pinghe Area,Southwestern Fujian

The Jinxi copper molybdenum polymetallic deposit is located in the southeast of Fujian province and the southeast of Shanghang-Yunxiao metallogenic belt.The ore bodies show a fairly simple shape and mainly occurred as quartz veins,and the distribution of the ore bodies is spatially related to Jinxi granitoids.We selected the Jinxi copper-molybdenum polymetallic deposit to conduct the detail study.Focusing on the geological characteristics,geochemical features of the Jinxi granites,chronology,fluid inclusions and stable isotope etc,in order to clarify the evolution of ore fluids,the genesis of the deposit and geodynamic settings.The Jinxi complex massif mainly includes granodiorite and granite.In this paper we report geochemical and petrological characteristics of the buried granite.These granites are characterized by rich in silica,alkali and negative in phosphorus.The granite's K₂O/Na2 O is 1.10¹.99,A/CNK is 0.97¹.04,belong to high fractionated I-type granite.The granodiorite's K₂O/Na2 O is 1.10¹.99,A/CNK is 0.97¹.04,belong to I-type granite.The trace element distribution curve of granite is similar to the granodiorite;They are rich in Rb,K and depleted in Nb,Ta,Ce,Ti;The REE show strong LREE/HREE fractionation,the granite has strong negative Eu anomalies,resulting in right-deviationist patterns.Comprehensive geochemical characteristics and regional comparative study,this paper think the granite and granodiorite could be homologous result of magmatic differentiation.Jinxi granite and granodiorite has the characteristics of crust-mantle mixed magma sources,both formed in stretch tectonic environment.We carried out zircon U-Pb ages for granitic rocks in the deposit.Zircon U-Pb dating yields ages of 103 Ma for granite,Precise Re-Os dating of molybdenite has also been carried out in this study.The results show that the Re-Os model ages is106.8±1.1Ma.These dating results suggest that the timing for the Cu-Momineralization and granite intrusion are simultaneou,which is corresponding to the period of the large-scale mineralization in the late period of early cretaceous.In this paper,We choose ore bearing quartz veins to test hydrogen and oxygen isotopic compositions and pyrite,chalcopyrite to test sulfur and lead isotopic compositions.Results show that the ?¹⁸O values range of 3.3 5.0 ‰,the ?D values range of 77.1 55.4 ‰ which is fall into Scope of magmatic water.The ?³⁴ has a small range of variation 3.7⁵.1‰,which has the characteristics of the deep magmatic sulfur.The 206Pb/204 Pb,207Pb/204 Pb,²⁰⁸Pb/ 204 Pb value were 18.458¹8.623,15.634¹5.705 and 15.705³8.973.A comprehensive of the lead isotope indicates that metallogenic materials of this deposit are related to magmatism,mianly derived from low crust but show the characteristics of crust-mantle mixing.Combining of Luoboling copper-molybdenum polymetallic deposit and chronology discussion of Mesozoic granites in south china,it infered that the formation of Jinxi copper-molybdenum polymetallic deposit has mainly connection with granitic intrusion ¹05 Ma).