Ore and Energy Resource Geology最新文献

The studied cassiterite-rich greisens of Mayo Darlé are hosted in granites located on the NE slope of the Guengue hill. They have three various structural forms including massive, vein, and stockwork. This study aims to describe all the different structural forms of greisen and also explains the main processes of greisen deposition related to the tin mineralization. The petrographic study shows that the massive form presents two facies: the massive greisens are rich and barren in cassiterite respectively; the stockworks and veins are all mineralized. The mineralogical composition recorded for each of the forms are Quartz + Muscovite + Cassiterite + Zinnwaldite + Plagioclase for the cassiterite-bearing greisen; Quartz + Muscovite + Tourmaline + Chlorite for the barren greisen and Quartz + Muscovite + Cassiterite + Tourmaline + Chlorite for the veins and stockworks. This mineralogy could indicate a varied chemical nature of the hydrothermal/magmatic fluids and the host granite. Also, the presence of minerals such as tourmaline, zinnwaldite and chlorite can equally indicate that there were three main stages in the granitic process: (i) tourmalinization, (ii) lepidolitization, and (iii) chloritization. The greisens have a chemical composition rich in SiO₂ (over 71 %) and Al₂O₃ (5.23–43 %). The chondrite-normalized REE pattern shows a negative Eu anomaly (0.0005–0.15) resulting from the disappearance of feldspars and biotite from the geochemical system, which is gradually transformed to quartz and chlorite respectively during leaching. The ratios of Rb/Sr, Zr/Hf, and Nb/Ta indicates an M-type tetrad effect, which also characterizes the variable values of the Eu anomaly. From a mining point of view, the areas most suitable for further prospection would be those hosting the massive, cassiterite-rich greisens. The significant occurrence of tourmaline and zinnwaldite in the studied greisens could indicate a possible Sn–W–Li polymetallic deposit.

The Pakbeng gold deposit, located at the junction of the eastern Tethys and western Pacific tectonic domains, is part of the Phôngsali-Luang Prabang-Sayaboury polymetallic metallogenic belt. Its gold ore bodies are predominantly governed by fault structures, being vein-like and short-axis-veined in shape. The Pakbeng gold deposit primarily exhibits two types of mineralized alterations: the quartz-vein type and the schistositized altered rock type. The ore bodies are primarily distributed within cataclastic granites and altered andesite plutons, near their contact zone. The ore-forming process can be divided into four stages: quartz + rutile + pyrite (stage I), quartz + pyrite + coarse-grained arsenopyrite (stage II), quartz + polymetallic sulfides + native gold (stage III), and calcite + quartz (stage IV). Native gold primarily occurs as invisible gold in the quartz and pyrite of stages I and II, and as enclosed, intergranular, and interstitial gold within the quartz, pyrite, and other metal sulfides of stage III. The ore-forming materials of the Pakbeng gold deposit primarily originate from plagioclase granites and altered andesites, as indicated by investigations of gold-bearing quartz fluid inclusions, hydrogen and oxygen isotopes, the trace-element composition of pyrite, and in situ sulfur isotopes. The sulfur in the deposit is mainly derived from metamorphic sources, supplemented by late magmatic sulfur. The ore-forming fluids in the deposit were dominated by metamorphic fluids in the early stage, with magmatic fluids participating in the late stage. While ascending, the temperature of the ore-forming fluids decreased due to fluid boiling and mixing, but their salinity increased slightly. The ore-forming fluids exhibited a consistent decrease in homogenization temperatures from stages I to IV, with salinity initially increasing and then decreasing. This suggests that the ore-forming fluids are low-temperature, medium to low-salinity and low-density fluids.

Alkaline rocks identified in the 414 U-Th deposit in Jianshui County, Yunnan Province, exhibit intense spatial correlation with uranium mineralization. However, limited investigations into their genesis have had an adverse impact on our understanding of uranium mineralization. Analyses of major and trace elements, U-Pb chronology, and petrography were conducted on alkaline rocks. The results indicate that anorthosite, which is rich in alkalis, high in potassium, peraluminous, enriched in rare earth elements (U, Th, Rb, and Zr) and deficient in Sr, Ba, Ti, and P, predominates the lithology. The light and heavy rare earth fractionation of the material is readily apparent (LREE/HREE=7.89–46.72), and the presence of Eu negative anomalies (δEu=0.65–0.81) suggests that the region from which the magma originated is a metasomatism-enriched mantle where the source material originates from the transition zone between garnet-lherzolite and spinel-lherzolite in the EMII-enriched lithospheric mantle. This area underwent metasomatization by subduction material from the Paleo-Pacific Ocean and during the ascent process, magma experienced a certain degree of partial melting and a significant degree of crystallization differentiation. The diagenesis of the syenite (186.64 ± 3.76 Ma) occurred after the closure time of the Paleotethys Ocean (237 Ma) in a dynamical context of an intra-terrestrial rift environment following subduction of the oceanic plate. In summary, the U and Th present in the 414 U-Th deposits underwent isomorphism within biotite and feldspars during the hydrothermal mineralization stage of magma evolution, where they were enriched in minerals through the separation and crystallization of alkaline magma.

The Toko-Nlonkeng area is situated in the Nyong Complex of the northwestern Congo craton. In this study, airborne geophysical data (radiometric and magnetic) and structural data (outcrops and core samples) were used to investigate the relationship between structural evolution, iron formation (IFs)-hosted iron ore deposits, and gold mineralization in the Paleoproterozoic Nyong complex greenstone belt in southwestern Cameroon. Magnetic and radiometric trends, combined with field data, show general NE-SW, NW-SE, and E-W directions that correlate with the main gold-bearing structures. The study area has undergone four (04) deformation phases relating to polycyclic metamorphic and magmatic events. The D₁ and D₂ phases are the result of progressive ductile and transpressional deformation; D₃ is a brittle-ductile deformation; and D₄ is essentially brittle with various types of fracture networks late to post-orogenic. The D₃ deformation phase is characterized by constrictive deformation with C₃ shears and meso‑ to mega-P₃-folds, and the main stress axes show φσ₂ > φσ₁> φσ₃, reflecting a shearing tectonic regime with a maximum E-W shortening. This polyphase deformation is derived from the Eburnean/Trans-Amazonian deformation related to the collision between the Congo and São Francisco cratons. The main strain in the structural style of the Nyong Complex appears to be transpressive tectonics. This study reveals that iron ore and gold mineralization were mostly found on the hinges of folds and confirms that folding shear zones controlled the iron ore and gold target in the Nyong Complex and Northeast Brazil. The study proposes an approach to optimize future exploration activity based on the integration of the data.

To assess the impact of nuclear fuel element processing on uranium(U) in the soil environment, a geochemical survey was conducted. The survey provided data on U concentration, speciation, Th/U ratio, and U and Pb isotopic composition in the soil around a nuclear fuel processing plant in Southwest China, which has been operational since 1965, to reveal the enrichment status and sources of U in the soil. The concentrations of Th and Pb in the soil were also compared. The average U concentration was 1.01-1.43 times that of the local background, and U existed primarily as residual U. The enrichment factor value indicates that U is slightly enriched in the soil. The Th/U ratio was higher than the crustal ratio and the world soil average value, indicating that some of the U in the soil has been lost due to surface runoff. The ²³⁵U/²³⁸U ratio distribution shows that a certain amount of ²³⁵U-enriched particles have sedimentation in the downwind direction of the plant soil, which results in a higher ²³⁵U/²³⁸U ratio in this direction. However, in general, the ²³⁵U/²³⁸U ratios were observed to be typical natural values. The ²⁰⁷Pb/²⁰⁶Pb ratio indicates that the U in the U ore enters the soil during nuclear fuel processing.

The Longjiang region is located on the eastern slope of the southern section of the Great Xing'an Range, in the transition zone between the Songliao Basin and Great Xing'an Range uplift. As it is an extension of the Inner Mongolia Linxi-Tuquan Cu-Mo-Pb-Zn metallogenic belt in the Heilongjiang region, it has conditions conducive to the formation of porphyry deposits. We report zircon U-Pb dating and whole-rock geochemistry data of magmatic rocks in representative mineralized points in the Longjiang region. Zircon U-Pb age shows that the age of magmatic rocks is concentrated in the Variscan period (312 ± 5 ∼ 294 ± 2Ma) and Yanshanian period (134 ± 2 ∼ 123 ± 1Ma). According to whole-rock geochemical analysis, the granites have SiO₂ contents of 61.2–69.16 % (66.9 % on average), Al₂O₃ contents of 13.87–15.98 %, MgO contents of 0.6–2.22 %, TiO₂ contents of 0.25–0.88 %, K₂O contents of 2.70–3.63 %, Na₂O/K₂O ratios of 1.05–2.05, and high K₂O+Na₂O contents (5.8–7.17 %), which are consistent with adakitic rocks. Yanshanian granites have A/CNK values of 1.02–2 and an average differentiation index of 84.7, which indicates that they are highly differentiated I-type granites. Variscan I-type granites represent the post-collisional setting of the Paleo-Asian Ocean and are relatively scarce in the region. Yanshanian highly differentiated I-type granites are products of the Paleo-Pacific Ocean's post-collisional retreat and are widely distributed in the region. As the materials and fluids that formed the Liujiushan, Haiyang, and Fendou deposits were derived from magmatic activities, and Variscan and Yanshanian magmas have excellent ore-forming potential. The highly differentiated I-type granites formed by intense Yanshanian magmatism are the most promising candidates for ore exploration in this region.

Monazite, a common U-containing ore-rich mineral found in association with U minerals, has excellent sealing properties after its formation, making it a promising tool for determining the age and genetic type of U mineralization. The Datian area in the Kangdian region of China is an important Neoproterozoic U ore-forming region. It has garnered the attention of researchers owing to the presence of megacrystalline uraninite with well-developed crystal forms. However, most studies conducted on U mineralization in the Datian area have focused on macroscopic observations and uraninite, with limited reports on accessory minerals. In this study, LA-ICP-MS U-Pb chronology and in-situ major and trace element analyses were performed on monazite associated with megacrystalline uraninite in the Datian area metallogenic belt I. The research yielded the following insights: 1) U mineralization in the Datian area was estimated to have occurred approximately 770 million years ago. This age demonstrates a potential correlation with the assembly and fracturing of the Rodinia supercontinent, suggesting a geodynamic context for the mineralization event. 2) The geochemical characteristics of the monazite indicate an igneous rock origin for its genetic type. Combined with previous research findings, it is postulated that U mineralization in the Datian area may be closely linked to the partial melting of deep crustal materials within a metamorphic environment characterized by high temperature and low pressure.

The exploration and development of mineral resources are of crucial significance to national economy, people's livelihood and national security. Therefore, in order to extract the weak signal in seismic exploration of non-coal solid mines in shallow surface layer to achieve high-resolution exploration, the mathematical model and physical model of multiplier are established by referring to the frequency point acquisition technology in wireless radar communication, that is, phase-locked technology. The weak effective seismic signals of different frequency points are picked out from the collected 120 dB dynamic range spectrum, and the information of stratigraphic structure under high noise background is obtained more effectively by using mixing detection and two-phase demodulation technology in the harmonic component spectrum, thereby improving the high resolution and high precision of mineral exploration. The lock-in amplifier is added to the front stage of the seismograph to obtain the effective seismic wave reflected by the wave impedance interface required in the exploration task. Experimental results show that this method significantly improves the SNR and protects the weak effective signal from loss. It adds new technology and method to seismic signal acquisition and processing, and provides a new way to obtain high-quality seismic data in the field of mineral geophysical exploration, and will be widely used after being promoted in the fields of mineral exploration, geological disaster prediction, military geophysics, and archaeology.

This study reports for the first time, Fe-Ti-V oxide and Cu-sulphide mineralization in Paleoproterozoic Mangikhuta basalt Formation, central Indian craton. Electron microprobe and laser ablation analyses of Fe-oxides reveal high FeO (45–69 wt %), TiO₂ (19–53 wt %), V (1860 - 4990 ppm), Zr (394–3130 ppm), Nb (55–285 ppm) and Zn (324–668 ppm). Interelemental relationships of Fe-oxides reveal their magmatic origin. High concentration of lithophile elements in Fe-oxides besides V and Ni trends in incompatible element plots indicate their origin from mafic melt. High Cu content (269 and 314 ppm) in the host basalt samples along with chalcopyrite mineralization observed during ore petrography indicates sulphide saturation of Mangikhuta magma. The chondrite normalized rare earth element (REE) plots of the host rock samples are overall similar to the earlier reported Mangikhuta REE patterns, which indicates genetic relation of Fe-oxides and Cu-sulphides with Mangikhuta volcanism. Fe-oxide and Cu-sulphide mineralization in Mangikhuta basalt is related to hydrous and oxygen rich arc related mafic melt intrusion into the Khairagarh back arc basin. Sulphide saturation in Mangikhuta basalt was initiated due to precipitation of Fe-oxides from the evolved melt whereas addition of fresh batch of hydrous and oxygen rich melt derived from the arc-related mantle source increased oxygen fugacity of residual melt that resulted in alternate phases of high oxygen and Sulphur fugacity and precipitation of Fe-oxide and Cu-sulphides from the melt.

After the end of the Cryogenian Snowball Earth glaciations, the Ediacaran Ocean experienced rapid oxidation and a subsequent increase in marine sulfate concentration. This led to a significant negative excursion in pyrite sulfur isotope values, particularly observed in the Doushantuo Formation of the slope facies in the South China. However, the extent of this oxidation event remains unclear. In order to address this, we carried out geochemical analysis of the Doushantuo Formation in the Cenpiaokou section of the Jiangkou County, Guizhou Province. In the Cenpiaokou section, the pyrite is mainly euhedral-subhedral and framboidal in crystal morphology. The pyrite contents are highest at the base of the Doushantuo Formation and decrease towards the middle and upper parts. Similarly, the proportion of framboidal pyrite also decreases upward, ranging from 93 % at the bottom to 9 % in the upper part of the Doushantuo Formation. Additionally, the sulfur isotope of pyrite (δ³⁴S) shows significant differences compared to other slope facies sections. There is no negative excursion in δ³⁴S at the base of the Doushantuo Formation. The lower part of the Doushantuo Formation exhibits frequent oscillations with generally high δ³⁴S values (+6.6 ‰ ∼ +37.3 ‰), while the upper part shows a decreasing trend. The organic carbon isotope (δ¹³C_org) displays an inverse correlation with δ³⁴S, with stable values in the lower part and gradually heavier values in the upper part. The nitrogen isotopes (δ¹⁵N) range from -1.6 ‰ to +2.1 ‰, suggesting a generally anoxic state with strong nitrogen fixation at the Cenpiaokou section. These findings suggest that the deep ocean oxidation during the early Ediacaran was not a global event, but rather a regional event, with anoxia still dominant overall.