Ore and Energy Resource Geology最新文献

Thirty sediment samples (11 on the surface and 19 from a 55 cm core) collected in the Dadu River, upstream of the Yangtze River, China, were analyzed by ICP-MS and Laser diffraction particle size techniques to determine heavy metal spatial-temporal distribution and particle size characteristics, respectively. The intent was to clarify the impact of human activities such as Pb-Zn mining and exploration on the distribution of potentially toxic elements (As, Cd, Cr, Cu, Pb and Zn) in adjacent fluvial deposits. Moreover, ²¹⁰Pb isotope dating was applied to study the historical variation and distribution of heavy metal pollution in a sedimentary profile in the middle section of the Dadu River. Results suggest that Cd concentration is notably high, exceeding by 16.3 times the soil background value in Sichuan Province, China, which can be intensified by Pb-Zn ore smelting. Surface sediments are mainly composed of silt, accounting for 79% on average, and relatively minor amounts of clay and sand. The fraction of clay in the downstream segments of the Dadu River is significantly higher than that upstream, indicating that the hydrodynamic force in the downstream region is relatively low compared with the upstream flow. Samples in the sedimentary profile, collected at 3 cm intervals, are mainly composed of silty sand, accounting for 75.6%, which comprehensively reflects the strong hydrodynamic force in this area. The results of ²¹⁰Pb dating of these samples indicate three intervals of historical fluctuation in heavy metal concentrations: 1950–1966, 1988–1991 and 1996–2006, respectively, which coincide to significant historical events (the Cultural Revolution, the construction of Pubugou reservoir and local smelting activities, and the implementation of environmental protection policies). Enrichment factor (EF) values of all heavy metals in the profile began to increase after 1994, and relatively high EF values of Cr and Cd indicated a significant enrichment due to increasing anthropogenic activities during this period. Our study demonstrates that anthropogenic activities can be well recorded in sedimentary profiles and provide new insights to retrieving the history of human developments.

Hong Kong International Airport (HKIA) is one of the busiest airports in the world, and much of its land is reclaimed from the sea, making it prone to uneven subsidence of the ground. Monitoring and predicting the subsidence of its surface are crucial for ensuring the operational safety of the airport. This paper firstly obtained the surface subsidence characteristics of the HKIA through applying the Small Baseline Subset Interferometry Synthetic Aperture Radar (SBAS-InSAR) technology, and then the spatial–temporal evolution was analyzed by using the Standard Deviational Ellipse (SDE) method. Moreover, the Long Short-Term Memory (LSTM) was employed to perform surface trend prediction of HKIA. The results show that the HKIA presents different levels of subsidence and uplift, with a maximum average subsidence rate of −64 mm/year and a maximum cumulative subsidence of −199 mm. The comparison between predicted curves and the actual subsidence revealed by InSAR from 2019 to 2023 is highly consistent, with the average absolute error and root mean square error less than 5 mm, and a coefficient of determination greater than 0.99. The LSTM model utilized in this paper can achieve reliable results in subsidence prediction based on time-series InSAR, and provide alternative means for geohazard prediction.

The Tethyan Himalayan metallogenic belt is a significant product resulting from the collisional orogeny between the Indian plate and the Eurasian plate. The region experienced three intricate tectonic-magmatic-mineralization stages: the 59–49 Ma Au mineralization stage, the 43–36 Ma Pb–Zn mineralization stage, and the post-collisional (25–0 Ma) Pb–Zn–Sb–Au mineralization stage. Among these, the post-collisional stage represents the most intense period of Pb–Zn–Sb–Au mineralization in the Tethyan Himalayan region. During this period, about 170 Pb, Zn, Sb, Au and Ag deposits (mineral occurrences) with different sizes and complex types were formed. An extensive analysis of isotope geochemical data from antimony polymetallic deposits within the metallogenic belt led to a comprehensive evaluation of the ore-forming fluids and mineralization processes for various deposit types in the belt. The diverse metal element enrichments and various metal deposit types in the metallogenic belt were not formed from a single fluid source. Instead, the ore-forming fluids showed characteristics of fluid mixing from multiple sources. The composition of these fluids primarily comprises formation water, magmatic water, atmospheric precipitation, geothermal water, and metamorphic fluid. However, there were similarities between the different deposit types. Ore-forming materials predominantly come from the crust, although contributions from the mantle to varying degrees have been observed. Deep magmatic fluids or metamorphic fluids within rocks play a crucial role in the ore-forming process. Simultaneously, by establishing the internal relationship between tectonic–magmatic events and Pb–Zn–Sb–Au mineralization, detailed studies on the characteristics of the ore-forming fluid and the ore-forming process were conducted.

Chrono-tectonic settings of the carbonatite occurrences of India are reviewed with a focus on the “big picture” of carbonatite emplacements in the Indian plate in relation to global tectonic events associated with the amalgamation and breakup of supercontinents. Four chrono-tectonic domains, namely, Southern domain, Southeastern domain, Northeastern domain and Northwestern domain, are delineated based on the geographical distribution, tectonic settings and temporal relationships amongst the carbonatite complexes. The Southern domain comprises two sub-domains – Paleoproterozic and Neoproterozoic. The Paleoproterozoic sub-domain is related to extension due to relaxation after the Southern Granulite Terrain-Dharwar accretion, while the Neoproterozoic sub-domain is related to rifting related to the fragmentation of Rodinia. The Southeastern domain is related to the Mesoproterozoic fragmentation of Columbia. The Northeastern domain is related to the Mid-Cretaceous breakup of Greater India from Australia-Antarctica driven by the Kerguelen mantle plume that also produced the Rajmahal-Sylhet Large Igneous Province (LIP). The Northwestern domain is related to the Late-Cretaceous Indo-Seychelles-Madagascar split and the passage of Greater India over the reunion hotspot, which also produced the Deccan LIP.

This study presents the recently discovered Wulao Shan Ordovician granite within the Lincang granitic batholith, discusses its geochemical affinity, genesis, and tectonic significance, and interprets the proto-Tethys orogenic model in southwest Yunnan. LA-ICP-MS zircon U-Pb analyses indicate a crystalline age of 473.0 ± 2.9 Ma for the Wulaoshan gneissic granite. Geochemical analyses show that the Wulaoshan granite exhibits relatively high SiO₂ concentrations (73.4–77.3 wt.%), strong peraluminous properties (ASI > 1.1), strongly Eu-negative anomalies, light and heavy rare earth fractionation, and relative Ba, Nb, Ta, Sr, P, and Ti depletion. SiO₂ and P₂O₅ exhibit a strong negative correlation, whereas Rb and Y-Th with a positive correlation. The magmatic zircons have negative εHf(t) values of -5.47∼2.74. Petrographic observations and whole-rock geochemical and isotopic analyses imply no aluminum-rich minerals such as cordierite, indicating that the Wulaoshan granite is a highly fractionated, high-temperature I-type granite, which may have formed via partial melting of the magnesian-iron igneous crust. Additionally, K-feldspar, plagioclase, and biotite within the granite samples may have undergone intense fractional crystallization. The Wulao Shan gneissic granite is an arc granite associated with subduction, indicating that the Lincang Block underwent proto-Tethys subduction. This finding provides evidence for proto-Tethys subduction down to the Lincang-Simao block and further supports the bidirectional subduction model of the proto-Tethys.

The East Region of Cameroon is a crucial area for mining activities. Over the past 20 years, there has been growing research into the potential environmental impacts of artisanal and small-scale gold mining (ASGM) in this region. Both in the short and long term, this type of mining can generate numerous health, environmental and socioeconomic impacts that can be measured using diverse methods. This study analyzes impacts of ASGM in some mining districts of this part of Cameroon through literature review. Four categories of mining-induced hazards have been considered: water and stream sediments, soil and mine tailings, health, society, and economy, and land use/cover change. The majority of studies have focused on the impacts on water and soil in the Betare-Oya and Batouri mining areas. Generally, the natural waters of Betare-Oya and Batouri are contaminated in Fe, Mn, Cu, Ni Cr and As, Cr, Pb, V, Zn, respectively. The soils in Betare-Oya are the most impacted by heavy metals due to the artisanal gold mining techniques employed. Point sources of contamination were identified to occur around active and abandoned mine sites. Additionally, socioeconomic and land use/cover risk assessments have been analyzed. The collaboration between different institutions and stakeholders can enhance the development of large databases, expertise, and technology for a better understanding of potential risks in the region and decision making. Finally, the use of GIS-based modeling for the assessment of mining-generated impacts should be expanded in the region. This approach is useful in handling geospatial data related to hazards caused by mining and for ensuring a long-term survey to monitor the evolution of contamination in natural waters, bottom sediments, and soils in the region.

Meymeh sideritic-ankeritic iron deposit in the eastern part of Malayer-Esfahan Metallogenic Belt (MEMB) is formed in the sedimentary-volcanic rocks of the Early Cretaceous sequence. Ore mineralization in the study area based on stratigraphic location and type of host rocks divided in two ore horizons. Lower ore horizon located in the dolomitic-sandy limestone (Kc₃) unit, which upper ore horizon is formed in thin-bedded limestone (Km) rocks. Petrographic studies indicates that mineralization comprises three ore facies: stockwork, bedded and massive ore facies. The most important primary minerals are siderite, ankerite, ferroan-dolomite, pyrite, pyrolusite, barite and minor chalcopyrite. The most frequent textures in the ore zones include laminae, replacement, vein-veinlet, massive and banded. Dolomitization and silicification are the main wall rock alteration styles; alteration intensity increases towards the ore zones. Based on relationships between ore minerals and rock forming minerals, ore mineralization (hypogene and supergene) in the Meymeh deposit formed during three main stages: fine-grained Fe-carbonate bands are intricately interlayered with dolomite beds. Sideritic-ankeritic bands exhibit classic sedimentary textures, such as laminations and bedding, indicative of a syn-sedimentary to early diagenesis origin. Coarser-grained stage two siderites and ankerites show breccia and vein-veinlet textures, and are considered to have formed by replacement during burial diagenetic sub-seafloor fluid flow. In stage three, siderite and ankerite were converted to secondary iron oxides such as oxide/hydroxide Fe minerals during meteoric water flow through the inverted normal and thrust faults and uplift. The primary two-phase fluid inclusions in the quartz-2 and ankerite-2 minerals that have been investigated from the ore mineralization section of the Meymeh deposit are homogenized at temperatures between 110.3 to 226.9 °C. Salinities of the primary fluid inclusions range from 3.39 wt.% to 14.77 % NaCl eq. This finding suggests that hydrothermal brine fluid mixing with seawater could be the primary mechanism that prompted ore formation. The similarity of REE patterns between siderite and ankerite in different ore facies and host rock carbonates indicates their derivation from the same ore fluids. The Meymeh deposit is considered a typical case of sedimentary hydrothermal diagenetic sideritic-ankeritic mineralization, in which minerals deposited when hydrothermal fluid was released from anoxic to suboxic water columns.

The Cuddapah Basin (CB) and its basement can be considered as an appropriate uranium metallogenic province. The basement complex of CB in the Eastern Dharwar Craton (EDC), India, has been the target for structurally controlled uranium exploration since the early 1980s. Most of the brittle-ductile deformation induced reactivated narrow linear fracture zones often exhibit significant surface and sub-surface uranium occurrence. There are about 10 fracture zones associated with uranium mineralization. Amongst them, the Kamaguttapalle–Kammapalle fracture zone (KKF) in the south of the CB is quite interesting from an exploration viewpoint with a suitable geologic setting in space and time frame. Geomorphic, structural and petro-mineralogic exploration guides imply the possibility of economic uranium concentration along the NNE-SSW trend where tectonic reactivation took place over pre-existing ductile shear zone. Progressive exhumation and transition from ductile to brittle deformation regime led to the development of dominant strike slip tectonics with an associated riedel fracture system, which are subsidiary coeval shear fractures used in depicting sense of movement. Intense illitization and hematitization are often observed. Quartz reefs and veins along the NNE-SSW trend cut the preexisting mylonites at places. About 9 stages of fracturing is observed out of which 3 stages are related to uranium mineralization. All the 9 deformations are related to strike slip tectonics which in turn is part of Grenville orogeny. Paragenetic sequence and mode of occurrences of uranium phases deciphers about the importance of low to moderate level epi‑meso type hydrothermal (100°–250 °C) fluids as carrier of U. Reactivated fractures and quartz veination also act as controlling factors of mineralization. Strain analysis points to positive and negative flower structures at different segments of the fracture zone. Based on the litho-structural attributes it is established that maximum compression (σ₁) acted along the NNW-SSE direction. Fractured quartz veins provide well defined permeability and trapping facility by restricting transverse fluid movement as a mechanical barrier. The presented model gives an idea on role of strike-slip tectonics in uranium mineralization for narrowing down the target zone for sub-surface exploration.

The Dharwar Craton (DC) is an archive containing a good proportion of ancient records of crustal evolution in its rocks. The greenstone-gneiss-migmatite and granitoid complex show significant variation in terms of time, space and mechanism of emplacement according to tectonics and geodynamic set up. The plutons of the northernmost part of Eastern Dharwar Craton (EDC) are especially recognizable from typical litho-structural attributes. The intensity of regional/burial metamorphism is negligible in these granitoids with versatile nature. Simple and composite plutons are demarcated on the basis of field association with distinguishable petro-mineralogy and geochemical characters. K-metasomatism in pluton is established from petrography with supportive geochemistry. Simple pluton is syenitic in nature unlike the composite plutons with lithological variation from Tonalite-Trondhjemite-Granodiorite (TTG) to alkali feldspar granite. The granitoids are developed from crustal melting during the plate convergence. Post-orogenic nature of syenite is indicated from geochemical data. The sharp contact between the plutons and country rocks indicates significant temperature difference between country rocks and emplaced magma. The characteristic features like brittle deformation dominated structures, sharp contact between emplaced plutons and country rocks, very low grade of regional metamorphism, intensely differentiated nature and absence of diatexitic migmatite indicate a shallow crustal depth of plutonic emplacement. Higher concentration of large ion incompatible elements (e.g., U, Th, K) and associated high heat production imply shallow crustal segment with rocks derived from evolved differentiated magma. The study indicates a depth less than 8 km and temperature condition less than 250°C which correspond to epizone, where uranium remobilization is facilitated.

The iron-rich manganese deposits of Libale area is located within the basement complex of North-central Nigeria. Mineralogically, the major mineral phases are: goethite (Fe₂O₃.H₂O), spessartine (Mn₃²⁺Al₂(SiO₄)₃), hematite (Fe₂O₃), and quartz (SiO₂), while minor mineral phases are orthoclase (Al₂O₃.K₂O.6 SiO₂), illite (KAl₂Si₃AlO₁₀(OH)₂), and manganite (Mn₂O₃.H₂O) suggesting a trend of mineral assemblage attributed to the differential mineralization of the iron-manganese deposit that may have been caused by the geochemical tectonic activity during its formation. Geochemically, on average, the Fe₂O₃, SiO₂, Al₂O₃, CaO, P₂O₅ content are 34.59 wt.%; 26.30 wt.%; 6.94 wt%, 2.60 wt%, 2.01 wt% correspondently while K₂O and TiO₂ are less than 1wt%. Suggesting oxide facies type for the deposit. The trace element composition of V (1040 ppm), Cr (100 ppm), Co (833.33 ppm), Cu (1740 ppm), Nb (1280 ppm), W (240 ppm), Ta (320 ppm) and Zr (302 ppm) were relatively high compared to Maro, Muro and Kakun BIFs in North-central Nigeria. Bivariate plot of Fe₂O₃ Vs. Al₂O₃, suggest enrichment of Fe₂O₃ but depleted in SiO₂ and Al₂O₃, which possibly indicates replacement of precursor silica and kaolinite with goethite which are subsequently dehydrated to hematite. Al₂O₃-SiO₂-Fe₂O₃ ternary diagram indicates Precambrian Banded Iron Formation (BIF) for the Libale iron- rich manganese deposits, this was confirmed by MnO Vs. FeO. Discriminative plots: FeO. SiO₂ - (FeO + MnO) - Fe₂O₃ and Al₂O₃+ K₂O + Na₂O Vs. MnO + FeO confirmed mixed facies as the analyzed data plots between silicate facies and magnetic-silicate facies, this is linked to chemical association between Al₂O₃ and SiO₂ for the iron-rich as it confirms a transitional grade of silicate facies to magnetite-silicate facies. SiO₂ Vs. Al₂O₃ plot revealed hydrothermal and diagenetic processes for its deposition. The iron-rich manganese deposit is of low grade iron (Av. Fe=24.19%) characterized by ferruginous manganese (Av. MnO₂=23.82%) based on the generalized percentages of element of major interest in assessing quality of iron and manganese ore, therefore, good for cast iron production.