| The Qinling molybdenum metallogenic belt is one of the important molybdenum metallogenic belts in China and even the world,and Huanglongpu molybdenum deposit is the earliest deposit closely related to carbonatite found in China.During the field geological survey,the author found the radioactive anomaly in the ore of Huanglongpu deposit.The uranium content of ore bearing carbonatite measured by energy spectrometer is between100×10-6～5400×10-6.In order to find out the occurrence characteristics and metallogenic age of uranium mineralization in Huanglongpu deposit,the following understandings are obtained through the analysis of petrography,mineralogy,geochemistry and isotopic chronology:（1）Three independent uranium minerals were found in the ore:brannerite,betafite and uranium.Brannerite is in irregular granular shape,with giant crystal grains in part;uranine is semihedral-heteromorphic granular,often coexisting with molybdenite and monazite,with a small amount of irregular granular and star-like pyrite at the edges.Iron ore;crystalline uranium ore is distributed in irregular grains or veinlets in uranite,molybdenite crystals or in the edge of niobium uranium ore.Common crystalline uranium-betafite-molybdenite or betafite-molybdenite-monazite or betafite-molybdenite-pyrite and other combinations.In addition to the above-mentioned independent uranium minerals,uranium may also exist in the form of adsorption or isomorphism（such as monazite,bastnaesite and other uranium-containing minerals）.（2）The uranium minerals in the ore are generally subjected to late alteration,and the brannerite is altered into Nb-containing ilmenite oxide;with the enhancement of the degree of alteration,the content of UO2 decreases,and the content of Nb2O5 and Ti O2 increases significantly;The uranium is formed in a high temperature environment,and the alteration is relatively weak.（3）Carbonatite and uranium-bearing carbonatite veins in this mining area are enriched with Ba,Sr,Sm,Y and other high-field-strength elements,and the rare earth element distribution pattern of carbonate rocks is characterized by rightward sloping and enrichment of light rare earths.Compared with ore carbonatite,its rare earth distribution curve is more gentle.The uranium content in the uranium-bearing carbonatite veins(with an average value of 5100×10-6)is significantly higher than that in the carbonatite(49.3×10-6),but the distribution of uranium minerals is uneven.（4）The uranium mineralization of the deposit is divided into two phases:the first phase of crystalline uranium deposits has a chemically weighted average age of 220.5±5.1 Ma（MSWD=0.60,n=15）and the U-Pb harmonic age of monazite is 216.7±3.2 Ma（MSWD=31.5,n=28）,consistent with the Late Triassic carbonatite diagenetic age,～220Ma,and the uranium mineralization is closely related to the carbonatite magmatic activity.This age is within the error range of the previous molybdenum ore age,indicating that the uranium and molybdenum mineralization of the Huanglongpu molybdenum deposit occurred under the same metallogenic event.The chemically weighted average age of the second-stage crystalline uranium deposits is 152.1±5.3 Ma（MSWD=0.45,n=15）,indicating that the Huanglongpu deposit also developed～150Ma crystalline uranium deposits,which are hydrothermal fluids produced by magmatic activities in the Yanshanian period Results of the activation transformation of early uranium minerals. |
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