Ore and Energy Resource Geology最新文献

Lithium is a critical mineral resource for development of hi-tech green energy technologies. Finland is one of the few EU countries with high potential for lithium mineral resources. Presence of significant lithium ore reserves within the rare-element granitic pegmatites classified as LCT (Li-Cs-Ta) pegmatites in the Kaustinen lithium province in Finland, makes it a substantial region for lithium resources in Europe. Hence the present study presents geochemical characterization of the Kaustinen lithium province for lithium exploration targeting. Results of multivariate statistical analysis applied to till geochemical data are presented. These map the geochemical signatures of (a) major lithostratigraphic units and (b) lithium-bearing spodumene pegmatites and differentiate them from the geochemical signatures of other potentially lithium enriched rocks such as mica schists, mica gneisses and granitoids in the region. Two unsupervised clustering algorithms are employed, namely principal component analysis (PCA) and factor analysis (FA). The results indicate that each lithostratigraphic unit is characterized by a distinct geochemical signature which is distinguishable in the factor and PC maps derived. The boundaries of the lithostratigraphic units in the PC and factor maps conform to the units mapped from the geophysical datasets.

This study demonstrates that FA and PCA of till geochemical data can be used for mapping bedrock lithology in poorly exposed terrains. Additionally, the factor analysis maps also differentiate the Li signature of the mica schists and gneisses of the basement complex from that of pegmatitic granite units, which are interpreted to be the source rocks of the spodumenepegmatite generating fluids. The FA highlights the spatial association of spodumene pegmatites with the mafic metavolcanic lithological units within the Evijärvi-Himanka thrust zone, indicating that the compressional regime during the Svecofennian orogeny in this region provided the structural architecture as well as pre-existing permeable pathways for the parental fluids of the spodumene pegmatites; while at the same time the competency contrast between mafic metavolcanic rocks (amphibolite) and surrounding schists in a compressional regime is interpreted to be one of the controls on the channelization and emplacement of the pegmatitic melts.

Due to the lack coupling analysis of heavy metals in soil-plant-atmosphere system, the migration and transformation of heavy metals remains unclear. In this study, 240 surface (0–20 cm) soil samples, 365 plant samples and 168 atmospheric dust samples were collected in a large coal mining area, in which selected heavy metals arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), plumbum (Pb), zinc (Zn) were analyzed, to elucidate the spatial distribution and source of heavy metals and their bioavailability. According to the results of ArcGIS mapping analysis, the distribution patterns of Cd, Cu, Pb, and Zn in the three media are similar, while the distribution characteristics of Cr and Ni are highly consistent. The factors contributing to these spatial distribution characteristics of heavy metals could be associated with human activities and the characteristics of the elements. Compared with the background value, Zn, Cr, Pb in soil, Zn, Cr, Cu in plants and Zn, Pb, Cu in atmospheric dust apparently accumulated. The geological accumulation pollution index (I_geo) shows that there exist mild to moderate levels of Cr and Cd pollution in soil, and mild to moderate levels of Cd, Cr, Pb, and Zn pollution in the air. The evaluation of potential risks of heavy metals showed moderate ecological hazards in soil and strong ecological hazards in atmospheric dust. The sources of heavy metals were assessed using principal component analysis (PCA), land use type, and spatial analysis. Anthropogenic factors are the main sources of heavy metal content. Coal-related industrial processes related to coal, sewage irrigation, the use of agricultural chemicals, and vehicle emissions may be anthropogenic sources of heavy metals.

The Xiaoyuzan deposit is a typical intermediate-sulfidation epithermal Au deposit in the Boluokenu metallogenetic belt. The orebodies are hosted by the Lower Carboniferous Dahalajunshan Formation volcanic rocks and controlled by the NW- and NNW-striking faults. The metal minerals present in the ores mainly include pyrite, sphalerite, galena, chalcopyrite, and tetrahedrite. The non-metallic minerals are primarily composed of quartz, calcite, and sericite. Three ore-forming stages are distinguished based on mineral assemblages, wall-rock alteration, and vein crosscutting relationships, including the quartz-pyrite stage (I) with silicification and propylitization, quartz-sulfide stage (II) with phyllic alteration, and quartz-carbonate stage (Ⅲ) with carbonatization. Three different types of pyrite are classified: coarse-grained PyI with cubic from the wall rock, fine-grained PyII with a crystal form of pentagonal dodecahedron in the quartz-sulfide veins, and coarse-grained cubic PyⅢ in the quartz-carbonate veins. The in-situ δ³⁴S value range of sulfides from stage I, stage II and stage Ⅲ are 5.0 ‰ to 5.5 ‰, 4.3 ‰ to 6.5 ‰ and 5.7 ‰ to 6.2 ‰, respectively. The composition of S isotopes indicates that the source of the sulfur is magmatic in origin, with main contribution from the host rock. All the types of pyrite are relatively enriched with Sb, Cu, Ag, Pb, Bi, and As. The composition of pyrite suggests that the Au in the pyrite present as lattice gold (Au⁺¹). The gradual decrease in Co contents from in PyⅠ, PyⅡ to PyⅢ indicates a gradual decrease in temperature during fluid evolution. The contents of trace elements in sphalerite are relatively low, with Fe, Mn, Cd, and Cu being relatively enriched. Using the sphalerite geothermometer (GGIMFis), the calculated temperature falls within the range of 303.0 to 334.3 °C. Pyrite II is characterized by the occurrence of oscillatory zones, suggesting rhythmic changes in fluid physicochemical conditions and compositions. Although coexisting of liquid-rich and vapor-rich aqueous inclusions were locally observed in stage II quartz according to previous studies, the absence of crustiform/colloidal/lattice bladed quartz in the main stage suggests that slight or gentle fluid boiling has occurred. In summary, it is proposed that fluid-rock reactions made great contribution for the precipitation of gold and sulfides in the Xiaoyuzan deposit.

Characterizing the leaching behavior and temporal variability of tailings is conducive to managing and preventing ionic toxicity to indigenous communities and environment. For this purpose, this work selected Cu-Pb-Zn tailings waste from Huili County, Sichuan province in China, as a research case, conducting a 60-day column leaching experiment to simulate the leaching behavior of the tailings. The results reveal that the weathering features of tailings, both salt-based ions and potential toxic elements (PTEs), could be subdivided into the rapid dissolution stage and carbonate dissolution stage. Additionally, acid rain can accelerate the weathering of calcite and dolomite, as well as the leaching of PTEs. The weathering of calcite precedes that of dolomite. A bulk release of PTEs occurs in the early stages, ranging approximately between 10.9 % and 33.6 % in the initial seven days, with As and Zn showing notable significance. Therefore, ecological effects of this abnormality necessitate thorough examination, given that the release of PTEs occurs over an extended and prolonged duration. Acid rain can promote ion desorption and weathering of major minerals, thereby facilitating the leaching of salt-based ions and PTEs. This study emphasizes the early rapid release stage of ions pollution from tailings, providing a preliminary understanding of the environmental impacts that may arise from tailings deposition and acidic rain leaching.

Urban-rural integration zones, situated at the interface between urban and rural environments, undergo profound alterations in arable soil quality attributed to rapid urbanization and intensified agricultural practices. However, there is still insufficiency research on potassium depletion from a spatial perspective, despite the increasing demand for vegetables. To address this gap, the spatial distribution characteristics of soils potassium in Tianfu New District, Chengdu Plain, China, were studied based on geochemistry, geostatistics and Earth system science. The results showed that: (1) Spatial heterogeneity existed in both soil total potassium (STP) and soil available potassium (SAP). However, there was no obvious spatial correlation between STP and SAP, and their spatial extents exhibited minimal overlap. (2) The STP levels are mainly affected by the altitude, slope, stratum exposure and geological background. (3) The SAP content is obviously affected by anthropogenic input, and the enrichment is significantly affected by fertilizers. This study reinforces the notion that the human intervention has strongly affected arable soil quality. The availability of fertilizer (e.g., potash) may significantly affecting food security within China.

The V-Ti-Fe mine tailings waste releases high concentrations of aquatic arsenic (As) ions to downstream ecosystems. The hydrogeochemical As simulation facilitates the prediction of toxicity (or redox state) and devising control strategies to mitigate the negative impacts. Therefore, this study utilizes the Wanniangou tailings pond (a V-Ti-Fe mine tailings reservoir) in the Panxi region, Sichuan province, China, as a case study to elucidate the As hydrogeochemical behaviour under varying pH and redox potential (Eh) conditions. Our study reveals that (1) the water-oxygen exchange and Mn are important to regulating the redox conditions in the filtrates. The Eh determines the valence states of As, which vary from reduced states to oxidized states during the runoff from the tailings pond to downstream (Rehe River). The flow of wastewater in Rehe River minimizes both the As toxicity and concentration, eventually improving water safety. (2) In a reducing environment, hematite exhibits a limited capacity for As(III) adsorption. In the case of oxidation conditions, goethite mainly adsorbed As(V), with an elevated adsorption capacity. Meanwhile, Fe-minerals remain relatively stable under varying redox and weakly acidic conditions. Consequently, targeted engineering interventions can achieve two crucial outcomes: (1) Minimize the acidity of the mine environment to retard the release of heavy metals from the tailings waste. (2) Prolonging the residence time of wastewater in Rehe River to promote the transition from a reducing state to an oxidizing state, thereby synergistically mitigating As toxicity.

The Neoarchaean (∼2.7Ga) migmatite melanosome of Jivumdnubanda area comprises anomalous radioactive elemental concentration. Significant amount of Th (68.54–290.85 ppm) and U (29.68–114.47 ppm) is observed within biotite-rich melanosome as inclusions. Radioelements are concentrated in certain accessory minerals e.g., allanite, apatite, xenotime and zircon. Leucosomal counterparts are devoid of such higher radioactive elemental concentration, which makes the study significant because the incompatible elements as well as the accessory minerals tend to go into the melt phases more preferentially. Each component of migmatite e.g., melanosome, leucosome and the diatexites are studied in detail from outcrops, under an optical microscope and by geochemical analysis. Structural deformation aspects are also taken care along with granite age determination to link the diatexite with anatexis timing. It is found that the migmatites formed around a pressure of ∼600 MPa correspond to a ∼20–22 km crustal depth when the hydrous mineral breakdown led to ∼50 % melting of evolved TTG protolith. Radiation-induced damage of the accessory minerals due to alpha decays destroyed the internal crystal structures at places. This metamictization and associated radiation damage of more or less refractory minerals along with deformation associated grain-scale fractures make easier to release mobile uranium during hydration and associated alteration at later stage. The presently observed radioactive elemental concentrations are the remnants left behind in the melanosome after leaching out of significant uranium.

Forearc mantle peridotites commonly undergo complex melt/fluid metasomatism, which inevitably has a considerable influence on their geochemical compositions at the whole-rock scale. Serpentinites predominantly comprise the Minhe ophiolite, which is a fragment of the Proto-Tethys Ocean that outcrops in the Qilian Orogen in NW China. These serpentinites contain zoned spinels that vary compositionally from the centers to the margins, with a spinel core overgrown by ferritchromite layer and magnetite at the outermost rim. The mineral chemistry of the spinel cores (i.e., Cr^#, Mg^#, Cr₂O₃, and Al₂O₃) suggests that the protolith of the serpentinites was an oceanic mantle remnant in a forearc setting. Moreover, the ferritchromite exhibited increases in Fe, Mn, Sc, and Ni contents and decreases in Mg, Cr, Al, V, Zn, and Ga contents. Considering the linear correlation among elements (e.g., Co, Ni, and Zn) and the absence of mineral inclusions, the ferritchromite likely formed through ionic substitutions induced by slab fluids. The magnetite was enriched in Cr, Ni, V, Zn, Co, and Cu, but did not have a magmatic origin owing to low V concentrations. All evidence indicates that the peridotites underwent at least two episodes of fluidic metasomatism in the subduction zone. During early slab subduction, aqueous fluids released from the dehydration of the subducted slab directly serpentinized the forearc mantle peridotites, thereby altering the olivine and orthopyroxene to lizardite/chrysotile. During this process, certain mobile elements (e.g., Fe, Ni, and Mn) in the fluids and/or olivine serpentinization were incorporated into existing spinels, favoring ferritchromite growth. The second fluidic episode was dependent on prograde metamorphism at greater depths in the subduction channel, which not only produced antigorite via the recrystallization of lizardite and chrysotile, but also drove the fluids towards a more oxidizing state, thereby facilitating the growth of Cr-magnetites. Subsolidus re-equilibration controlled by fluid infiltration further promoted the inter-diffusion of elements (e.g., Cr, V, Co, Ni, Cu, and Zn) in the zoned spinels.

The Birimian Supergroup (2195–2135 Ma) of Ghana was affected by the Eburnean Tectono-thermal Event at approximately 2195 Ma. The latest stage of this event resulted in pegmatitic veining in the Birimian Supergroup of Ghana at 2072 Ma. Deposits of pegmatites have been reported by many researchers in the south-western coast of Ghana. However, their mineralogy and economic potential remain fully unexplored. This study determined the geochemical characteristics and mineralogical composition of the pegmatites in the Winneba-Mankoadze area using field observations, petrographic studies, and major and trace element data. From the field work and petrographic data, the pegmatites can be classified as rare-element type, LCT family. The modal composition of the major minerals are spodumene (0.0–30.0 %), muscovite (0.0–20.0 %), garnet (0.0–5.0 %), microcline (0.0–20.0 %), plagioclase (6.0–70.0 %), and quartz (20.0–85.0 %). The geochemical data indicates that the pegmatites are enriched in Rb (2.8–3465 ppm), Cr (22–1803 ppm), Sr (1.2–314 ppm), Ba (13–501 ppm) and the light rare-earth elements (LREE). The pegmatites are highly fractionated accounting for the enrichment in the LREE than the MREE and HREE. They are also depleted in K and Ti. The pegmatites are peraluminous with calc-alkaline trend and are late-orogenic to post-orogenic. Therefore, the source of the pegmatites is the Birimian meta-sedimentary rocks, and the source lithology is upper-to-middle crust supracrustal rocks.

The Luanhe River Basin is the most mined region in China, and spatial analysis of mine areas is beneficial for identifying hotspots of mining-related threats and assessing their impacts in this catchment. From an Earth system science perspective, we examined the spatial clustering of mine areas and the interactions between geographical attributes in the Luanhe River Basin. The findings are: (1) the total mine areas in the Luanhe River Basin are approximately 368.5 km² (2749 polygons), primarily located in the middle and lower reaches. (2) The Global Moran's I for scale and mining land of mine areas in the Luanhe River Basin is 0.04 and 0.45, respectively. This indicates that the scale of mine areas is randomly spread in the basin, while the mining exhibits clustering property. Consequently, clustered mine areas cover approximately 207 km² (56.1 %), while randomly distributed mine areas cover ∼161.5 km² of land (43.9 %). (3) A merged region is formed when the buffer distance of mine areas exceeds 2 km, potentially creating contiguous mining threat areas. This research provides a dataset for managing and governance mine areas in the Luanhe River Basin.