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The Huangsha uranium mining area is located in the Qingzhangshan uranium-bearing complex granite of the Middle Nanling Range, Southeast China. This uranium mining area contains three uranium deposits (Liangsanzhai, Egongtang, and Shangjiao) and multiple uranium occurrences, showing favorable mineralization conditions and prospecting potential for uranium mineral resources. Chloritization is one of the most important alteration types and prospecting indicators in this mining area. This study aims to unravel the formation environment of chlorites and the relationship between chloritization and uranium mineralization, based on detailed field work and petrographic studies of the wallrock and ore samples from the Huangsha uranium mining area. An electron probe microanalyzer (EPMA) was used in this study to analyze the paragenetic association, morphology, and chemical compositions of chlorite, to classify chemical types and to calculate formation temperatures and n(Al)/n(Al + Mg + Fe) values of chlorite. The formation mechanism and the relationship with uranium mineralization of the uranium mining area are presented. Some conclusions from this study are: (1) There are five types of chlorites, including the chlorite formed by the alteration of biotite (type-I), by the metasomatism of feldspar with Fe–Mg hydrothermal fluids (type-II), chlorite vein/veinlet filling in fissures (type-III), chlorite closely associated with uranium minerals (type-IV), and chlorite transformed from clay minerals by adsorbing Mg- and Fe-components (type-V). (2) The chlorite in the Huangsha uranium mining area belongs to iron-rich chlorite and is mainly composed of chamosite, partly clinochlore, which are the products of multiple stages of hydrothermal action. The original rocks are derived from argillite, and their formation temperatures vary from 195.7 °C to 283.0 °C, with an average of 233.2 °C, suggesting they formed under a medium to low temperature conditions. (3) The chlorites were formed under reducing conditions with low oxygen fugacity and relatively high sulfur fugacity through two formation mechanisms: dissolution–precipitation and dissolution–migration–precipitation; (4) The chloritization provided the required environment for uranium mineralization, and promoted the activation, migration, and deposition of uranium.

The Yuqia uranium deposit is a newly discovered sandstone-type uranium deposit in the northern margin of the Qaidam Basin. Concerning the sources of sediment in the basin, most scholars have focused on the study of Cenozoic sediment sources in the northern part of the basin, rather than on the study of Jurassic provenance and its implications for uranium mineralization. In this paper, the Jurassic sandstones in the area were selected for petrography, petrogeochemistry and electron microprobe analysis (EPMA), and the significance of sedimentary provenance and uranium metallogeny were further discussed, based on the previous data of detrital zircon chronology. It is reported here for the first time that coffinite and pitchblende are the main contributors. Independent uranium minerals in the region mainly occur in strawberry pyrite, xenotime, and margins or of quartz. The rocks in the source area, Jurassic sandstones, were mainly formed under the tectonic setting of the active continental margin; however, the sediments are mainly derived from the Indosinian and Paleozoic granitoids exposed in the northern margin of the Qaidam Basin. The uranium-rich granites in the source area led to the preconcentration of uranium in the sandstone of the target layer, and the uranium was brought into the ore-bearing target layer through uranium-bearing oxygenated water. The reduction reaction occurred under the action of reducing matter, and finally, the U6+ was reduced to U4+ in the formation of coffinite and pitchblende.

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The Jiadi gold deposit, situated in the Southwestern region of Guizhou, is a large-scale, recently discovered, basalt-hosted, and fine-grained disseminated gold deposit. This study has unveiled that the tectonic deformation of the Jiadi gold deposit can be categorized into four stages: the Late Paleozoic crustal uplift and brittle deformation (D1-deformation) stage; the Early Yanshanian NW-trending compressive ductile deformation (D2-deformation) stage; the Late Yanshanian NS-trending strike-slip fault (D3-deformation) stage; and the Himalayan EW-trending nappe structure (D4-deformation) stage. The outcomes of the C-O isotope analysis revealed that the fluid responsible for ore formation exhibits the attributes of magmatic water blended with meteoric water, and the metallogenic constituents primarily originate from a deep source. The formation of the Jiadi gold deposit occurred during the D2-deformation stage and extended to the D3-deformation stage. The D2-deformation stage induced hydrothermal activity and rock devolatilization, leading to the generation of CO2-rich and low-salinity fluids. The D3-deformation stage, which is intimately associated with mineralization, can be classified into three stages: the pyrite stage; the smoky quartz stage; and the sulfide stage. The findings obtained from laser Raman spectroscopy indicate that the inclusions typically comprise CO2, CH4, N2, and SO2. These deep fluids ascended along the fault to the interlayer fracture zone during the D3-deformation stage. The alteration of the geochemical environment was accompanied by fluid immiscibility or boiling, resulting in the rapid precipitation of metallogenic materials.