This paper is the result of mineral exploration engineering.

Objective Tengchong is the first area in China to achieve a breakthrough in ground leaching experiments on sandstone−type uranium ore, yet the origin of the uranium ore remains controversial. To analyze the characteristics of uranium mineralization, explore the patterns of uranium ore formation, and promote the effective implementation of subsequent exploration efforts.

Methods This paper discusses the uranium mineralization processes based on sedimentary facies logging, geochemical analysis and electron probe microanalysis (EPMA) of core samples from 10 boreholes in the Hanbazhai area of the Longchuanjiang Basin and the Langpuzhai area of the Lianghe Basin.

Results it is concluded that uranium in Hanbazhai district is mostly adsorbed, and uranium minerals are mainly unidentified nano−scale minerals with chemical formula generally close to Ca₂U₄ (SiO₄)₃ (PO₄)₃, and uranium mineralization is controlled by the combination of "fault−hydrothermal and lower organic−rich layer". Uranium in Langpuzhai district is mostly in adsorbed state and form of uranium minerals, including phosphuranylite, autunite, coffinite, pitchblende and brannerite. Uranium mineralization is influenced by the "fault−hydrothermal and lower organic−rich layer" and the emplacement of mafic rocks (veins). The further investigation reveals that uranium enrichment and metallogenesis persist in the shallow strata strong reduction zone through deep reducing fluid transportation along the fault. Additionally, uranium mineralization is basically spatiotemporally coupled with the mafic volcanic rocks (veins) with the geochemical characteristics similar to intraplate basalt. Combined with the preliminary understanding that the Li−U−Au symbiont enrichment in Tengchong hot spring indicates that there may be "modern mantle plume" in Tengchong, we proposed that the sandstone−type uranium deposits may belong to "Earth core source − mantle plume" origin. That is, uranium metal in the outer core in the form of uranium hydride or uranium alloy hydride upward migration along the mantle plume, shallow fault−hydrothermal (reduction fluid) and mafic rock (vein) introduction, enrichment and mineralization in favorable structural−lithologic superposition.

Conclusions It is concluded that the area with radioactive water chemistry anomalies in the northern part of Tengchong still has considerable potential for uranium mineral exploration in the sandstone type. It is suggested to initiate a pilot project for extracting uranium from groundwater for the 381 deposit, which has the characteristic of long−term exploitable nature due to the continuous replenishment of uranium sources by groundwater.