Lantian Uranium Ore Field In North Qinling Mountains Metallogenic Belt Of Ore-controlling Tectonic Geochemistry Characters And Studying Mineralization Model

Lantian uranium ore field is the most important granite-type uranium concentration area,which is also the uranium ore field with relatively higher research degree, miner geneticconditions favorable for granite-type uranium and the best resource exploitation andutilization conditions. Based on collecting results from previous studies, the mining area wasconducted field work and study. The following are some ideas:1.Muhuguan rock mass located in Lantian uranium ore field belongs to high alkalineperaluminous granitoids of the calc-alkaline suite, its REE patterns decline to right with slightnegative Eu anomaly and highly incompatible elements are enriched, especially Rb and Th;weakly incompatible elements are depleted.2.The faulted structure can be distributed into four stages according to the character offracture tectonic system in mining area. The first phase: EW oriented fractures（F1）; Thesecond phase: N-E oriented fractures（F2）; The third phase: NE（F3-1）and NNE orientedfractures; The forth phase: NW oriented fractures（F4）, among which NNE and NE orientedfractures constitute the main structure and form three NNE-NE cambered fault zones whichcontrol the main ore deposits and constitute the main structure in the mining area，areequidistantly distributed in the space.3.The distribution of uranium deposits: controlled mainly by the compound fractures ofNNE and NW fractures and secondary paralleled fractures developed near the main fault zone.The impulse deposits occurred in a scope of certain level and distributed in two types: one isupper converging and lower diverging; the other is against it. On the whole, the occurrence ofore bodies is characteristic with side-pitching, consistent with the fractures, and controlled bythe fracture zone.4.Compared with the biotite granite, samples of host rocks in mining area are Si and TFedeficited, Al and K enriched, Na slightly enriched, Ca changes near the averaged value, andthe ratio of K₂O and Na₂O are more than1, which indicated that the rocks had experiencedalkali metasomatism. Compared with the host rocks, Si in samples of ore rocks content riseobviously, Na enriched, K slightly deficited, Al is the main element taken out and is deficited;Fe₂O₃rise slightly, FeO slightly enriched, the ratio of Fe₂O₃and FeO rises. 5.REE patterns of mineralization and host rocks decline to right，with weakδEuanomaly； REE patterns of ore rocks also declines to right, with positive δEu anomaly. Totalrare earth content continues to reduce during metallogenic process. The rocks are all U, K, Pbenriched and Ba, P, Ti depleted.6.The results of clustering analysis and factor analysis are consistent in3midpieces of104ore deposit. The element geochemistry behavior of U is similar to that of W、Mo、As、Pb、Sb、Zn, inside of which W and As are the most similar elements to U. The elements fittingwell with U content of variant elements in different taconites are only Pb and W, next is As,which may serve as direction elements of uranium enriched to a certain degree. Theenrichment coefficient of Ni、Ta、Zr、Hf、Li、Be、W、Mo、Nb and U is all higher the abundancein the crust, only the coefficient variation of U is more than1.7.Lantian uranium ore deposit shares a great deal in common with the southerngranite-type uranium ore deposit, whose mineralization model is: pre-enrichment of uraniumrock bodies–activated-migration of the uranium-bearing hydrothermal solution-precipitationand form uraninite-denudation and leaching in the earth’s surface.