Jiling U deposit, Longshoushan Uranium ore zone, Jinchuan District, Jinchang, Gansu, Chinai

Regional Level Types
Jiling U deposit	Deposit
Longshoushan Uranium ore zone	Zone
Jinchuan District	District
Jinchang	Prefecture-level City
Gansu	Province
China	Country

Uraniferous albite veins, hosted in the contact zone between an Early Palaeozoic diorite-granite massif and Lower Proterozoic marble and biotite-quartz schist.

The Jiling uranium deposit covers an area of 0.8 × 1.5 km in the southern central part of the Longshoushan belt. The deposit was discovered in the late 1960 s. The deposit has resources over 1500 tU with low-grade uranium ore (0.03–0.1 wt% U), which have been greatly increased by recent exploration. The uranium ores and related altered rock assemblages are hosted in the Na-metasomatism zones adjacent to the F101 fault. Alteration zones are distributed along the footwall of the F101 fault, with no uranium mineralization in the hanging wall of the fault. The orebodies are complicated in terms of quantity and morphology, with over forty orebodies in lens or irregular shapes arranged in an echelon configuration. These orebodies varied considerably in size and thickness (meters to decameters thick), and were not continuous due to the presence of F105. These orebodies can be grouped into two clusters of the eastern (exploration lines 9–17) and western (exploration lines 21–33). The orebodies of the Jiling deposit are mostly concealed with only the easternmost No. I orebody exposed to the surface, and most orebodies are mainly concentrated between 1800 m and 2300 m. The hydrothermal alteration of the Jiling uranium deposit is intensive and mainly consists of albitization, chloritization, hematitization and carbonatization.

Five stages of magmatic and hydrothermal evolution at Jiling: (1) the first stage involved the emplacement of the Jiling high-K calc-alkaline granitoids, representing the primary uranium source for mineralization; (2) Na-metasomatism stage is characterized by the albitization accompanied by ductile deformation. The alteration assemblage includes albite, hematite, and chlorite. U–Pb dating of apatite from ore-barren albitite yielded an age of 433 ± 14 Ma. Stable isotopes of albite and chemical compositions of apatite indicate that the metasomatic fluids were high-temperature, Na-enriched, and alkaline, likely exsolved from the mafic dykes in the Jiling area; (3) Na-Ca-metasomatism followed immediately after Na metasomatism. This stage, characterized by weak brittle deformation of the albitite, is associated with high-temperature uranium mineralization. Alteration assemblage includes albite and calcite, with uraninite as the primary uranium mineral. Uranium was transported by a high-temperature, alkali-rich, alkaline, and reducing fluid, primarily as hydroxide complexes. The removal of Na and Ca from the fluids destabilized uranium complexes, leading to uraninite precipitation; (4) Ca-Fe-Mg-metasomatism, occurring during the Middle Devonian, is associated with the low-temperature uranium mineralization. Alteration minerals include calcite, chlorite, hematite, and barite. Pitchblende is the dominant uranium mineral. Metasomatic fluids were primarily meteoric water with a minor magmatic component. Uranium was likely transported as uranyl sulfide complexes; (5) the post-ore alteration stage contains calcite, chlorite, illite, and quartz. During this stage, uraninite and pitchblende were partially or totally altered into coffinite.

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