A Comparative Study On The Characteristics Of Granite Porphyry In The South And North Of Xiangshan Uranium Ore Field,Jiangxi Province

Porphyry type uranium deposit is one of the main types of uranium deposits in Xiangshan uranium field,Jiangxi Province.The deposits have been concentrated in the northern part of Xiangshan ore field.The southern Xiangshan area is distributed with granite porphyry which is similar to that in the northern area,but the research degree is relatively low.The possibility of a major breakthrough in uranium prospecting in this area is divided.Based on the comparative study of field geology,lithology,principal and trace elements,Sr-Nd-Pb isotope and diagenetic age of granite porphyry rocks in the south and north of Xiangshan,the source of magmatic materials,tectonic environment and petrogenetic types of granite porphyry rocks are analyzed,and the possibility of uranium mineralization in the south of Xiangshan is discussed.It is found that the granite porphyry bodies in the South and north of Xiangshan have similar petrographic characteristics except for slightly different outcropping scales.The rocks are fleshy red or gray-white,with patchy or plaque-like structures.The phenocryst minerals are mainly composed of quartz,potassium feldspar,plagioclase and biotite.The mineral composition and characteristics of the matrix are the same as those of the phenocrysts.The edges of quartz phenocrysts are corroded in sub-circular shape and distributed in the form of speckles.The euhedral crystal degree of K-feldspar is similar,and the characteristics of plagioclase and biotite are basically the same.Electron microprobe studies show that the compositional characteristics of the rock-forming minerals(biotite and plagioclase)in the granite porphyry in southern and Northern Xiangshan are similar.The measurement points of the plagioclase sites in Hengjian intrusion fall into the category of albite area.The measurement points of the plagioclase sites in other intrusions fall in both albite area and medium-feldspar area.The biotite is poor in Ti(Ti < 0.45)and AlVI(AlVI < 0.55).Both of them have high Si content and low Ti,Fe,Mn and Mg content and both belong to high iron biotite.The granite porphyries in the South and north of Xiangshan have similar geochemical characteristics and diagenetic epochs.The rocks are rich in silicon and alkali,belonging to the quasi-aluminous-peraluminous K-basaltic series and the high-potassium calc-alkaline series,which are highly characterized by crystallization differentiation and evolution.The standardized cobweb maps of trace elements in the original mantle show that Th,U,Pb,La,Rb,Nd are positive anomalies and Ba,P,Ti,Sr are negative anomalies.U and Th were significantly high.The ?REE of rocks is higher than crust and has strong fractionation of light and heavy rare earth elements.The normalized distribution pattern of REE chondrites is "seagull type" with negative Eu anomaly.The initial ratio of 87Sr/86 Sr is similar to the mean value of the continental crust,with ?Sm/Nd from-0.54 to-0.40,and low ?Nd(t),207Pb/204 Pb is greater than 15.6.LA-ICP-MS zircon U-Pb dating shows that the diagenetic ages of granite porphyry in the South and north of Xiangshan are the same,ranging from 132 Ma to 137 Ma,belonging to the Early Cretaceous period.It is considered that the granite porphyry in the South and north of Xiangshan have the same material source,genetic type and tectonic setting.The magma originated mainly from crustal materials.The genetic types of rocks belong to the transitional type(A-S type)between A-type granite and S-type granite.The formation environments are intraplate tectonic environments formed by retreating magma intrusion after subduction of the Pacific plate.The main reason for the lack of major breakthroughs in prospecting is that the workload of deep exposure is insufficient.In view of the above,it is considered that the granite porphyry in southern Xiangshan has the possibility of uranium mineralization,and the major ore bodies may still be located in the deeper part.The main reason for the lack of major breakthroughs in prospecting is that the workload of deep exposure is insufficient.