Ore and Energy Resource Geology最新文献

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.

The stream sediment geochemistry has a wide application in mineral exploration. In this study, we applied the stream sediment geochemistry to decipher the primary source of gold mineralization, determine the mineralogy of heavy mineral concentrate and also to ascertain the provenance, depositional environment, intensity of weathering as well as determine the tectonic setting. To investigate heavy mineral in stream channel, 20 placer materials from Bidjouka area were assessed by thin plate using polarized microscope. The powder was further characterized by ICP-MS using aqua regia. Results show that placers displayed minerals such as magnetite, zircon and gold. Majors geochemical base metal point out low grade of iron (< 5 wt.%), titanium (< 1.05 wt.%) and alumina (< 0.60 wt.%). The following metallic trace elements used for industrial technology are identified in the samples. It mainly concerns manganese and thorium with content less than 328 and 200 ppm respectively as well as mercury (< 550 ppb). Precious metals are also present in the chemical composition of Bidjouka sediments. The main substances identified is gold with the grade above 2 g/tone, which is an important target in mining exploration. Also the mean value of rare earth elements varying between 1256.6 and 3626.8 ppm are so speculative, with negative and positive Eu and Ce anomaly respectively. Gold is bound with sulfide mineral (Au-Bi), suggesting a sulfidation event during sediments deposition. Factor 4 (Co, Mn, Sc, Au, Bi) refers to the mineralization factor and Co, Mn, Sc, Bi serve as pathfinder of gold. Sediments were deposited under humid, oxic and oxidizing conditions; intermediate intensity of weathering processes of the source rocks had prevailed during deposition, and sediments were rich in plagioclase. These continental sediments have quartzose sedimentary provenance, they were originated from metamorphic sources and were deposited in an active continental margin. The results of this study serve as guide for gold exploration and exploitation in the Bidjouka area.

The Rössing-Husaib area is well-known for its low-grade and large-reserve U deposits hosted by leucogranites. The leucocratic dykes in the Kang-dian area of China resemble the Rössing-Husaib uraniferous leucogranites in occurrences and mineral assemblages, however, it remains disputable if the Rössing-Husaib and Kang-dian leucocratic rocks have consistent U-mineralizing processes. A comparison of the major and trace element data of the leucocratic rocks from both areas may help to better understand the ore-forming mechanisms and provide implications for exploration in the Kang-dian area. The positive correlation between Rb and P₂O₅ contents for the Rössing leucogranite samples is typical of S-type granitoids in spite of the low A/CNK ratios (∼1.0). The Rössing-Husaib uraniferous leucogranites are generally rich in K₂O and Rb, and have high Rb/Sr and Rb/Ba ratios. In contrast, the Kang-dian leucocratic dykes have lower K₂O and Rb contents, and lower Rb/Sr and Rb/Ba ratios, suggesting a clay-poor source. The U contents of the Rössing-Husaib and Kang-dian dyke samples are positively correlated with TiO₂ contents, but show no correlation with Rb/Sr ratios, which is inconsistent with fractional crystallization. Low-degree partial melting of a U-rich protolith may account for primary U enrichment in the leucocratic rocks. The variable major- and trace-element compositions of the Kang-dian dyke samples may reflect wall-rock assimilation and/or alteration to varying degrees, which further enhanced U enrichment. Relatively low Th/U ratios (∼0.1) favored the final crystallization of uraninite. The uraniferous leucogranites in the Kang-dian and Rössing-Husaib areas are commonly undeformed and emplaced along regional large faults and/or domes at the late stage of orogeny. We propose that decompression and uplift of basement rocks facilitated the generation of uraniferous melts, and regional large faults provided a pathway for the ascent of leucocratic magma from depth.

It is generally agreed that the unconformity-related uranium (URU) deposits in the Athabasca Basin (Canada) resulted from reactions between basin-derived, oxidizing, U⁶⁺-bearing fluids and reducing agents carried by basement-derived fluids or lithologies enriched in reducing elements. Based on the observation that most URU deposits are spatially associated with graphite-rich zones in the basement, it is believed that either the graphite itself or hydrocarbons derived from it acted as major reducing agents for U mineralization. Several previous studies downplayed graphite as a direct reducing agent for U mineralization because few or no direct contacts between uraninite and graphite have been observed. However, it remains skeptical whether or not this is due to insufficient observation, and what happened to the graphite if it was not directly involved in U precipitation. In this study, graphitic metapelite samples were collected from the Gryphon URU deposit for detailed petrographic and Raman spectroscopic study. Two types of graphite were identified, an earlier phase (Gr1) that is parallel and deformed together with the schistosity, and a later phase (Gr2) that is post-deformation, both of which are pre-U mineralization. Thorough microscopic examination confirmed that there is no direct contact between uraninite and graphite in the thin sections. Raman spectroscopic studies of the graphite indicate that the structural order of both Gr1 and Gr2 decreases toward the orebody. These observations indicate that graphite was not a direct reducing agent causing the precipitation of uraninite. Hydrocarbons (mainly CH₄) produced from in situ fluid-graphite reaction was not responsible for the uraninite precipitation either, because such a process would also have produced textures showing replacement of graphite by uraninite. Instead, the graphite initially present in the host rocks that are now occupied by the orebodies was likely dissolved by the hydrothermal fluids ahead of the precipitation of uraninite. The actual reducing agents causing the precipitation of the bulk of uraninite in the orebodies are likely CH₄ derived from ex situ fluid-graphite reaction below the deposit.