The Study On Geological Characteristics And Metallogenic Regular Of Zhangmajing Uranium-molybdenum Deposit In Northern Hebei Province

Zhangmajing uranium-molybdenum deposit is an important uranium deposit in northern area of China, and it is located in the northern margin of the North China Craton, which is also located in the west of the Yanshan-Liaoning metallogenic belt. This paper is about the study of geologic feature and metallogenic regularity of Zhangmajing deposit with the aid of the project <Researches on the comprehensive assessment technology of uranium and polymetallic deposits in the northern margin of North China Craton >. In this paper, the features of wall rock, tectonic framework, ore body, ore petrology, wall rock alteration and element geochemistry are studied systematically on the basis of field geological investigation and previous information. Metallogenic regularity is investigated on the basis of finding out mineralogenetic epoch, the source of metallogenic material and mineralization process. The acquired achievements are listed as follows:(1) Uranium mainly comes from volcanic lava and volcaniclastic rock in Zhangjiakou Formation and rhyolite porphyry, which are the product of the anatexis of the crust and main wall rocks rich of U ore.(2) Tectonic framework is important precondition for the formation of this deposit. Fault F45 obviously controls the distribution of strata, deposits and volcanic edifice in this region. And there is the volcanic edifice that rhyolite porphyry invaded into and is the ore fluid channel and the host space, where F45 intersects with second fault F3.(3) There are various altered minerals in wall rock of Zhangmajing deposit, including low-to-moderate temperature minerals, and alteration types are potassic zone, argillization zone and silicification zone around the ore-bearing porphyry outwardly.(4) There are the richment of Fe, Ti, Mn, P and so on, and the correlation between U element and In, Bi, Be, Cr, Co, Ni, V, Cu, Sc, Cs, Ga, Th, Zn in ore. And there is also obviously severer depletion of Eu in ore than in rhyolite porphyry.(5) Three uranium mineralization periods in zhangmajing deposit: the first uranium mineralization is closely related to the formation of rhyolite porphyry; the second uranium mineralization belongs to hydrothermal vein type; the third uranium mineralization is secondary enrichment of the first-period uranium ore bodies, which belongs to leaching type.(6) The key uranium ore-forming conditions of zhangmajing deposit are: the volcanic edifice, fault structure, hypabyssal(or super hypabyssal) porphyry body and volcanic rock of Zhangjiakou Formation.