[en] Through systematic drill core observation, section contrast and analysis,it is proved that the ore-controlling interlayer oxidation zone of Qianjiadian uranium deposit is mainly composed by the red oxidized sandstone and locally distributed yellow and off-white sandstones. The red sandstone contains charcoal fragments, pyrite, ilmenite, siderite, which have been oxidized intensively, and it can be deduced that their original color was gray and became red due to the oxidization. The distribution of the oxidation zone is mainly controlled by the sedimentary facies,which also controll uranium metallization. The uranium orebodies mainly developed in the thinning or pinch parts of the red oxidation zone in section. On the plans, the uranium mineralization distributes near the front of the red interlayer oxidation zone. (authors)

[en] Qianjiadian uranium deposit is a sandstone-type uranium deposit that has been discovered in Songliao Basin in recent years. Uranium ore bodies are planar or lenticular in shape and under the control of the contact between gray sandstones and bleached sandstones. The bleached sandstone is white in color, cemented loosely, nearly without TOC and pyrite contained and rich in uranium. Geochemical characteristics and types and assemblages of clay minerals of the bleached sandstone reveal that the bleached sandstone is the product of oxidation of the interlayer oxidation zone, and it is a part of the interlayer oxidation zone. The main reasons for white color of the bleached sandstone are transfer of iron ion, oxidation of TOC and kaolinization of sandstone. (authors)

[en] According to the data of drill cores, outcrops and well logging, two orders base-level cycles are recognized from Zhiluo Formation in Dongsheng area, which consist of 8-14 short-term base-level cycles and 3 mid-term base-level cycles, and their structural types and stacking patterns are discussed by using principles and methods of high-resolution sequence stratigraphic theory. Based on the correlation of mid-term base-level cycles, the control of the A/S (Accommodation/Sediment supply) ratio in mid-term base-level cycles on the scale of sand bodies and physical properties of reservoir is analysed. Studies show that the sand bodies of braided stream in MSC1 of Zhiluo Formation are favourable to uranium mineralization, however, the sand bodies of meandering river in MSC2 and MSC3 are not favourable to uranium mineralization. The change of the A/S results in the difference in characters of sand body, such as physical properties, continuity and so on, which control the fluid flowing path. After discussing the immigration of uranium-bearing oxidizing ground water in the braided channel sand bodies, the paper tries to present the answers to the question of why the host orebody occurs mainly in the middle and upper sand body which the lower limb is thicker than the upper limb in the limb orebodies. (authors)

[en] The Dongsheng uranium deposit in the Ordos basin, Northern China occurs in fluvial sandstones in the lower member of the Zhiluo Formation, Middle Jurassic. Uranium ore bodies are mostly located at or near the contact between gray sandstones and gray greenish sandstones. The high contents of Fe²⁺ in gray-green host sandstones are considered as the most important reason why those sandstones are in gray-greenish or green color. In mineralogical aspects, there are more clay minerals, especially more chlorite in gray-green sandstones. Research data of petrology, mineralogy and geochemistry show that gray-green sandstones were altered by the epigenetic reducing alteration in the Dongsheng region. It is proposed that the gray-greenish host sandstones were previously oxidized sandstones and subsequently reduced by introduced fluids. The reduction process covered up the previously oxidized sandstones and protected uranium accumulations from the destruction by infiltrating oxidizing water. It is stated that the reduction process in the Dongsheng area was simultaneously and genetically related with the formation and development of the Hetao down-faulted basin located to the north of the Ordos basin. Uranium mainly occurs in uranium minerals and adsorption form. Data of the electron microprobe and X-ray powdered crystal analysis show that uranium minerals are mainly coffinite, minor brannerite and pitchblende. Uranium-lead isotopic ages of the uranium mineral--coffinite in high-grade ores of the uranium deposit are centered at Miocene time between 20 Ma and 10 Ma. A 'Multi-stage Uranium Mineralization' model is proposed by authors for uranium ore-formation of the deposit. The mineralization process could be divided into four main stages, namely the pre-concentration during diagenesis, the interlayer infiltration mineralization during Late Jurassic to Paleocene time, the reconcentrate in Miocene, and the last stage of ore preservation exerted by reducing fluids after Pliocene time. (authors)

[en] Yunji deposit is a typical alkali metasomatic uranium deposit in Xiangshan ore-field, and the chlorites are closely related to uranium mineralization. Based on detail mineralogical observation, the chemical composition of chlorite was analyzed with electron microprobe. The forming environment of chlorite and its geological significance were discussed and concluded. Chlorites in Yunji deposit can be divided into chlorite altered from biotite and chlorite growing along cracks and microfractures. The both belong to iron rich femic chlorite and pycnochlorite which indicate that they are formed in a relatively reduced environment. The chlorite was formed in the temperature from 188 to 244℃ with average of 213℃, fall in the meso-thermal-epithermal range. From pre-ore formation stage to ore formation stage, Fe in chlorite was tend to be replaced by Mg which suggest that the hydrothermal fluid gradually become relatively more alkaline. The formation of chlorite was believed mainly by the mechanism of dissolution-crystallization and dissolution-migration-crystallization. (authors)

[en] Partial extraction geochemical prospecting method was used to evaluate the uranium mineralization prospect and three uranium abnormal zones was outlined from north to south and joining together in the north of Guangdong. Satisfied prospecting results and several industrial uranium drilling holes have been obtained in the big uranium abnormal area by drilling. 4 geochemical prospecting indicators were developed for the exploration of granite-type uranium deposit by partial extraction geochemical prospecting method, which will play a more important role in the uranium exploration of deep buried ore and second prospecting space. (authors)

[en] Through studying the characteristics of pyrite and sulfur isotope in the rock of Upper Cretaceous Quantou Formation, Yaojia Formation and Nenjiang Formation in the southeastern Songliao Basin, occurrence features of pyrite and characteristics of sulfur isotope in gray and grayish-green sandstone produced by epigenetic reducing decoloration of Quantou Formation and Yaojia Formation indicate the characteristics of organic fluid composition in deep-seated oil-gas and coalbed methane. δ³⁴S_V-CDT of sulfur isotope in original sedimentary diagenite is positive, δ³⁴S_V-CDT of organic fluid in oil-gas and coalbed methane is negative. Reduction of oil-gas and coalbed methane not only makes mottled and purplish-red original oxidized sandstone reduce to grey and grayish-green reducing sandstone, which makes the reducing capacities of rocks increase greatly, but also uranium is superimposed and enriched during the interaction of rocks with organic fluid of oil-gas and coalbed methane and uranium content increases generally, which results in the forming of uranium anomaly and mineralization in some areas. Stockwork damouritization is discovered in the ore-bearing sandstone of Yaojia Formation in Menda area at the first time, which shows the uranium mineralization is characterized by low temperature hydrothermal alteration and is related with low temperature hydrothermal fluid. (authors)

[en] The red oxidation zone may be formed in the process of the interlayer oxidation. If the original gray beds formed in the moist palaeoclimatic condition and became red in oxidation, it is easy to distinguish this red oxidization zone from the original red beds. Gray sandstone sandwiched by red mudstone can be formed partially in the arid-semiarid condition. If this gray sandstone was oxidized to be red in color, almost all the strata would be red in cross section, and then it will be difficult to distinguish these red strata from the original red beds. If they are regarded as original red beds, we maybe lose the favorable opportunity to find uranium deposit. This paper presents a case study of Yaojia Formation, Upper Cretaceous in the southwestern part of Songliao Basin. Although the palaeoelimatic condition was arid-semiarid, the gray sandstones of Yaojia Formation in Qianjiadian Sag and its adjacent areas have obvious characteristics of primary depositional origin, and part of them may be formed by epigenetic reduction. The gray sandstone has formed red interlayer oxidation zone after being oxidized and it is just the red interlayer oxidation zone which controls the uranium mineralization in Qianjiadian uranium deposit. By careful contrast and analysis, identification marks of red epigenetic oxidation beds have be established, which can effectively help the distinguishing of epigenetic oxidized red beds from original red beds and extends prospecting idea. (authors)

[en] Based on the study of typical hydrothermal uranium deposit of uranium-hematite-type and uranium-pyrite-type, this paper discussed the redox conditions of hydrothermal uranium mineralization. The minerals combination of uranium-hematite-type deposit formed in alkali metasomatism from Xiangshan ore field are pitchblende-hematite-sodium feldspar-apatite-carbonate, while in acid metasomatism the mineral composition are pitchblende-hematite-lepidocrocite-micro quartz as in Changjiang ore field. And the uranium-pyrite-type ores are consist of pitchblende-pyrite-micro quartz-fluorite. The uranium-hematite type ores was formed earlier than the uranium-pyrite type. Both types of uranium ore are abundant in the deep and shallow parts of the ore deposit, and they have a superimposed distribution feature in the vertical direction. The redox condition of pitchblende existing stably from pyrite to the coexistence area of pyrite and hematite, besides, pyrite area is favorable for pitchblende enrichment whereas the complete hematite area is not conducive to the precipitation and preservation of pitchblende. (authors)

[en] Through the integrated interpretation of element variation coefficient, R mode cluster analysis and factor analysis, the characteristic of element anomaly was analyzed using the basic geochemical data of stream sediment survey (1:50000) in Nanxiong area. Nanxiong area has good metallogenic potential for Bi, Mo, Pb, W, Au, Cu and Sn. According to the comprehensive analysis of some important parameters, such as the area, the average contrast and the sum of the normalized areal productivity of integrated anomaly, a scale of integrated anomaly was quantitatively ranked. With consideration of the geological background, three potential prospecting sectors were delineated, which are Miantuwo W-Mo-Cu, Yazizhai-Tianyaodi W-Mo-U, and Quan'an Sb-Pb. (authors)