Characteristics Of Tangang Volcanic Rock In Central Jiangxi And Comparative Study With Volcanic Rock Of Xiangshan Uranium Ore Field

Tangang Volcanic Basin in central Jiangxi is located at the Southwest end of Gan-Hang uranium metallogenic belt,with an area of about 20km² and about 20km from southwest of Xiangshan uranium ore field.The predecessors have carried out some basic geology and uranium ore prospecting work here,and they believe that Tangang Volcanic Basin has certain uranium metallogenic potential.However,lithology,petrography,geochemistry,chrono-logical characteristics and formation tectonic environment of main volcanic rock in Tangang Basin is still controversial.In particular,there is a lack of systematically comparative research on related volcanic rocks in Xiangshan uranium ore field.So,there has been no breakthrough in the prospecting work.This paper selects main volcanic rock in Tangang Volcanic Basin as the research object,systematically determines lithology,petrography,geochemistry,chronology and other characteristics of volcanic rock,and discusses its magmatic origin,source properties,and formation tectonic environment.On this basis,through a systematic comparative study with related volcanic rock in Xiangshan uranium ore field,this paper discusses uranium metallogenic possibility.The research shows that main volcanic rock in Tangang is gray,massive structure,and clastoporphyritic texture,mainly including quartz（20%±）,plagioclase（10%±）,biotite（5%±）,with felsitic texture of basis.The clastoporphyritic texture of quartz is well developed,and darkening phenomenon of biotite is well developed.The volcanic rock contains a small amount of metamorphic breccia（1%±）,which is clastoporphyritic lava of overflow facies.In terms of geochemistry,main volcanic rock in Tangang is rich in Si（ω（Si O₂）=66.80%～72.25%）and rich in K（K₂O/Na₂O=1.68～2.34）.It belongs to high potassium calc-alkaline series,and is Quasi-aluminum to Weak-overaluminum.The total amount of REE is relatively high(ΣREE=238.1×10^-6～318.8×10^-6),which has the characteristics of LREE enrichment（LREE/HREE=7.98～10.55）and moderate negative Eu anomaly（δEu=0.41～0.47）.It is deficient in Ba-Ta-Nb-Sr,but enriched in Rb-Th-Nd-Zr-Hf,with characteristics of low Sr(100×10^-6～243.90×10^-6)and high Yb(3.16×10^-6～6.23×10^-6).In terms of Sr-Nd-Pb isotopes,I_Srvalue（0.71107～0.71139）is high,ε_Nd（t）value（-8.16～-7.60）is low,Δβvalue（19.28～20.06）is high,andΔγvalue（42.66～44.37）is high.LA-HR-ICP-MS zircon dating results show that the diagenetic age of Tangang volcanic rocks is between 137.1Ma and 137.6Ma,which is early Early Cretaceous.Among them,the formation age of Northern volcanic rock in Tangang is 137.3±0.6Ma,the formation age of Eastern volcanic rocks is 137.1±0.6Ma,and the formation age of Southern volcanic rocks is137.5±0.6Ma.The study believes that diagenetic material of Tangang volcanic rock mainly comes from Upper Crust,with Higherε_Sr（t）value（95.60～100.10）and lowerε_Nd（t）value（-8.16～-7.60）,and Upper Crust material accounts for about 77%.It is speculated that some mantle-derived materials may be mixed.The magma belongs to the category of S-type granites,which is consistent with characteristics of Zhemin-type granites.It is the product of magmatic activity in continental extensional environment caused by the retreat of Paleo-Pacific plate.Compared with the characteristics of related volcanic rock in Xiangshan uranium ore field,it is found that in addition to slightly lower Si O₂ content and slightly higher Al₂O₃content of rocks,the lithology,petrography,geochemistry,chronology and other characteristics of the main volcanic rocks in Tangang are basically consistent with the corresponding characteristics of the transitional facies clastoporphyritic lava of Ehuling Formation（K₁e）in Xiangshan uranium ore field,and both are products of regional magmatic activities of the same period.In addition,Tangang basin has the same characteristics of structural background,ore controlling structure,hydrothermal alteration and uranium source as Xiangshan uranium ore field,and many uranium mineralization anomalies have been found,indicating that research area has good uranium mineralization and prospecting potential.