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The eastern Central Asian Orogenic Belt (CAOB) in NE China is a key area for investigating continental growth. However, the complexity of its Paleozoic geological history has meant that the tectonic development of this belt is not fully understood. NE China is composed of the Erguna and Jiamusi blocks in the northern and eastern parts and the Xing’an and Songliao-Xilinhot accretionary terranes in the central and southern parts. The Erguna and Jiamusi blocks have Precambrian basements with Siberia and Gondwana affinities, respectively. In contrast, the Xing’an and Songliao-Xilinhot accretionary terranes were formed via subduction and collision processes. These blocks and terranes were separated by the Xinlin-Xiguitu, Heilongjiang, Nenjiang, and Solonker oceans from north to south, and these oceans closed during the Cambrian (ca. 500 Ma), Late Silurian (ca. 420 Ma), early Late Carboniferous (ca. 320 Ma), and Late Permian to Middle Triassic (260–240 Ma), respectively, forming the Xinlin-Xiguitu, Mudanjiang-Yilan, Hegenshan-Heihe, Solonker-Linxi, and Changchun-Yanji suture zones. Two oceanic tectonic cycles took place in the eastern Paleo-Asian Ocean (PAO), namely, the Early Paleozoic cycle involving the Xinlin-Xiguitu and Heilongjiang oceans and the late Paleozoic cycle involving the Nenjiang-Solonker oceans. The Paleozoic tectonic pattern of the eastern CAOB generally shows structural features that trend east-west. The timing of accretion and collision events of the eastern CAOB during the Paleozoic youngs progressively from north to south. The branch ocean basins of the eastern PAO closed from west to east in a scissor-like manner. A bi-directional subduction regime dominated during the narrowing and closure process of the eastern PAO, which led to “soft collision” of tectonic units on each side, forming huge accretionary orogenic belts in central Asia.
In this contribution, detailed field descriptions together with petrographic and bulk-rock major, trace and rare earth elements (REE) data are used to constrain the origin and geodynamic setting of the mafic magmatic enclaves (MMEs) recently discovered within the Pan-African Ngaoundal pluton, Adamawa area, central Cameroon. The investigated MMEs are dark-colored with chilled margins, and display medium to coarse-grain igneous textures. The mineral assemblage is either dominated by K-feldspar and carbonate (group I), or by amphibole and plagioclase (group II), though the overall mineral phases made of amphibole, plagioclase, K-feldspar, and biotite are similar to that of their host syenite but in different proportions. The MMEs in Ngaoundal area are foid-gabbro in composition with SiO2 contents ranging between 41.52% and 43.74% and are contiguous with their host granitoids of intermediate composition (SiO2=57.52% to 58.98%). The host granitoid rocks are metaluminous, and belong to the shoshonitic series. Petrographic and geochemical data have revealed that the Ngaoundal MMEs derived from rapid cooling of hot injected lithospheric mantle-derived magma within cooler host granitoids magma and were emplaced in the intraplate geodynamic setting.
By the end of 2020, 83 silver deposits (or ore occurrences), including four super-large-scale deposits, nine large-scale deposits, 33 medium-scale deposits and 37 small-scale deposits or ore occurrences, have been proved. The amount of silver metal exceeds 86000 t with average grade of 100 g/t, which makes Daxing’anling region one of the the most important silver ore belt in China. However, the metallogenic characteristics and metallogenesis need to be clarified. The silver deposits in the study area are classified into three main types, which are magmatic hydrothermal vein type, continental volcano-subvolcanic type and skarn type, respectively. The supergiant deposits include the Shuangjianzishan deposit (silver metal amount of 15214 t with average grade of 138 g/t), the Baiyinchagandongshan deposit (silver metal amount of 9446 t with average grade of 187 g/t), the Huaobaote deposit (silver metal amount of 6852 t with average grade of 170 g/t), and the Fuxingtun deposit (silver metal amount of 5240 t with average grade of 196 g/t). The silver deposits are mainly distributed in the central and south of the Daxing’anling area, and mainly formed in the Yanshanian period. The silver polymetallic deposits in the Daxinganling area are significantly controlled by regional faults and the junction zone of volcanic rock basins and their margins. The north-east trending deep faults are the most important ore-controlling structures in this area. The distribution of silver polymetallic deposits along the main faults is obvious, and the intersection area of multiple groups of faults often form important mine catchments. The Permian is the most important ore-bearing formation in this area, but some important silver polymetallic deposits occur in Mesozoic volcanic basins or pre-Mesozoic strata. The magmatic rocks related to mineralization are mainly intermediate acidic or acidic intrusions, intermediate acidic lavas, pyroclastic rocks, and small intrusions of ultra-shallow or shallow facies of the Yanshanian Period. The mineralization element combination is mainly determined by the elemental geochemical background of surrounding rocks or source layers. In addition, the type of deposit, the distance from the mineralization center, and the degree of differentiation of ore-forming rock mass are also important influence factors. The article analyzes the prospecting prospects of each silver deposit type in the study area, discusses the relationship between mineralization center and deep prospecting, and proposes that porphyry silver deposits should be paid attention to. In the prospecting and exploration of silver deposits, comprehensive evaluation and multi-target prospecting need to be strengthened because silver can coexist or be associated with a variety of metals.
Landsat 8 Oli, ASTER, and Sentinel 2A satellite images processing was used to map geological formations, lineaments and hydrothermal alteration minerals in the Aouli inlier, as a case study to illustrate the application of digital images processing and Geographic Information System (GIS) in geological mapping and mining prospecting. Principal Component Analysis (PCA) applied to the Landsat images allowed good lithological discrimination and contributed to the updating of available geological maps. The Automatic lineament extraction from Sentinel images revealed the main tectonic structures affecting Aouli inlier. The ratio bands (b5+b7)/b6 and the false color composite (b4/b6, b2/b1, b3/b2) allowed the hydrothermal alteration minerals mapping from Aster images. Combined with available geological data and field observations, the satellite derived data were integrated and analyzed in a GIS software to establish mining prospecting guides. The results showed that the anomaly zones are intimately linked to NNE–SSW and NW–SE oriented faults and to highly fractured areas developing argillic and Fe rich alterations. Verified via field survey, this approach was successfully applied to the Aouli inlier to rapidly target potential areas to be explored in the tactical phase. This provides a model for future prospecting efforts for similar mineral deposits in other areas.
In this work, the authors monitored the formation and dissociation process of methane hydrate in four different rock core samples through nuclear magnetic resonance (NMR) relaxation time (T2) and 2D imaging measurement. The result shows that the intensity of T2 spectra and magnetic resonance imaging (MRI) signals gradually decreases in the hydrate formation process, and at the same time, the T2 spectra move toward the left domain as the growth of hydrate in the pores of the sample accelerates the decay rate. The hydrate grows and dissociates preferentially in the purer sandstone samples with larger pore size and higher porosity. Significantly, for the sample with lower porosity and higher argillaceous content, the intensity of the T2 spectra also shows a trend of a great decrease in the hydrate formation process, which means that high-saturation gas hydrate can also be formed in the sample with higher argillaceous content. The changes in MRI of the sample in the process show that the formation and dissociation of methane hydrate can reshape the distribution of water in the pores.
Based on the 16 scenes GF-1 satellite multi-spectral remote sensing images, through the adoption of data processing methods including orthorectification, geometric rectification, data fusion and image mosaic, integrated with field surveys, the remote sensing interpretation signs for the inland wetland types have been built, and the remote sensing survey of inland wetlands in Yadong region has been initiated, with six types of inland wetlands recognized in Yadong region, namely permanent rivers, seasonal rivers, lakes, salt lakes, alpine meadows, and inundated land. The spatial distribution characteristics and the spreading rules of these wetlands have also been revealed. Based on full understanding of the overall characteristics of the inland wetlands in the Yadong region, using the three phases of TM images acquired in 1989, 2003 and 2008 as well as the PMS2 data gathered by GF-1 in 2014, and the wide-range data (WFV3) gathered by GF-1 in 2020. As to the typical salt lakes, a long- time salt lakes transition study was carried out. The results show that the typical salt lakes in Yadong have been shrinking in the past three decades. The average annual shrinkage of Duoqing Co (Co means lake in Tibetan) was stronger than that of Gala Co, which are respective 87.30 hectares (usually short as ha; 1 ha equals to 0.01 km2) /a and 24.20 ha/a; the shrinkage degree of Gala Co was higher than that of Duoqing Co, shrank by 59.27% and 35.73% respectively. Based on the remote sensing survey results and an integrated analysis of the predecessors’ researchers, the reason for the shrinkage of the salt lakes is more inclined to geological factors. Geological process is manifested by a series of extensional faults at the bottom of the lake basin generated from tectonic activities, providing fluid infiltration channels, and inducing the eventual leakage of lake water to the lower strata. The result provides an important instance for understanding the evolution characteristics of wetlands and salt lakes in specific environment of the Tibetan Plateau.
In this paper, 25 sampling points of overlying deposits in Tonglushan mining area, Daye City, Hubei Province, China were tested for heavy metal content to explore pollution characteristics, pollution sources and ecological risks of heavy metals in sediments. A geo-accumulation index method was used to evaluate the degree of heavy metal pollution in the sediment. The mean sediment quality guideline quotient was used for evaluating the ecological risk level of heavy metal in the sediment. And a method of correlation analysis, clustering analysis, and principal component analysis was used for preliminary analysis on the source of heavy metal in the sediment. It was indicated that there was extremely heavy metal pollution in the sediment, among which Cd was extremely polluted, Cu strongly contaminated, Zn, As, and Hg moderately contaminated, and Pb, Cr, and Ni were slightly contaminated. It was also indicated by the mean sediment quality guideline-quotient result that there was a high ecological risk of heavy metals in the sediment, and 64% of the sample sites had extremely high hidden biotoxic effects. For distribution, the contamination of branches was worse than that of the main channel of Daye Dagang, and the deposition of each heavy metal was mainly influenced by the distance from this sample site to the sewage draining exit of a tailings pond. The source analysis showed that the heavy metals in the sediment come from pollution discharging of mining and beneficiation companies, tailings ponds, smelting companies, and transport vehicles. In the study area, due to the influence of heavy metal discharging from these sources, the ecotoxicity of heavy metals in the sediment was extremely high, and Cd was the most toxic pollutant. The research figured out the key restoration area and elements for ecological restoration in the sediment of the Tonglüshan mining area, which could be referenced by monitoring and governance of heavy metal pollution in the sediment of the polymetallic mining area.
The porphyry copper belt in the Geza island arc in southwestern China is the only Indosinian porphyry copper metallogenic belt that has been discovered and evaluated so far. The Pulang porphyry copper deposit (also referred to as the Pulang deposit) in this area has proven copper reserves of 5.11×106 t. This deposit has been exploited on a large scale using advanced mining methods, exhibiting substantial economic benefit. Based on many research results of previous researchers and the authors’ team, this study proposed the following key insights. (1) The Geza island arc was once regarded as an immature island arc with only andesites and quartz diorite porphyrites occurring. This understanding was overturned in this study. Acidic endmember components such as quartz monzonite porphyries and quartz monzonite porphyries have been identified in the Geza island arc, and the mineralization is mainly related to the magmatism of quartz monzonite porphyries. (2) Complete porphyry orebodies and large vein orebodies have developed in the Pulang deposit. Main orebody KT1 occurs in the transition area between the potassium silicate alteration zone of quartz monzonite porphyries and the sericite-quartz alteration zone. Most of them have developed in the potassium silicate alteration zone. The main orebody occurs as large lenses at the top of the hanging wall of rock bodies, with an engineering-controlled length of 1920 m and thickness of 32.5‒630.29 m (average: 187.07 m). It has a copper grade of 0.21%‒1.56% (average: 0.42%) and proven copper resources of 5.11×106 t, which are associated with 113 t of gold, 1459 t of silver, and 170×103 t of molybdenum. (3) Many studies on diagenetic and metallogenic chronology, isotopes, and fluid inclusions have been carried out for the Pulang deposit, including K-Ar/Ar-Ar dating of monominerals (e.g., potassium feldspars, biotites, and amphiboles), zircon U-Pb dating, and molybdenite Re-Os dating. The results show that the porphyries in the Pulang deposit are composite plutons and can be classified into pre-mineralization quartz diorite porphyrites, quartz monzonite porphyries formed during the mineralization, and post-mineralization granite porphyries, which were formed at 223±3.7 Ma, 218±4 Ma, and 207±3.9 Ma, respectively. The metallogenic age of the Pulang deposit is 213‒216 Ma. (4) The petrogeochemical characteristics show that the Pulang deposit has the characteristics of volcanic arc granites. The calculation results of trace element contents in zircons show that quartz monzonite porphyries and granite porphyries have higher oxygen fugacity. The isotopic tracing results show that the diagenetic and metallogenic materials were derived from mixed crust- and mantle-derived magmas.
The Dayin’gezhuang gold deposit is located in the central part of the Zhaoping Fault metallogenic belt in the Jiaodong gold province—the world’s third-largest gold metallogenic area. It is a typical successful case of prospecting at a depth of 500‒2000 m in recent years, with cumulative proven gold resources exceeding 180 t. The main orebodies (No. 1 and No. 2 orebody) generally have a pitch direction of NNE and a plunge direction of NEE. As the ore-controlling fault, the Zhaoping Fault is a shovel-shaped stepped fault, with its dip angle presenting stepped high-to-low transitions at the elevation of −2000‒0 m. The gold mineralization enrichment area is mainly distributed in the step parts where the fault plane changes from steeply to gently, forming a stepped metallogenic pattern from shallow to deep. It can be concluded from previous studies that the gold mineralization of the Dayin’gezhuang gold deposit occurred at about 120 Ma. The ore-forming fluids were H2O-CO2-NaCl-type hydrothermal solutions with a medium-low temperature and medium-low salinity. The H-O isotopic characteristics indicate that the fluids in the early ore-forming stage were possibly magmatic water or mantle water and that meteoric water gradually entered the ore-forming fluids in the late ore-forming stage. The S and Pb isotopes indicate that the ore-forming materials mainly originate from the lower crust and contain a small quantity of mantle-derived components. The comprehensive analysis shows that the Dayin’gezhuang gold deposit was formed by thermal uplifting-extensional tectonism. The strong crust-mantle interactions, large-scale magmatism, and the material exchange arising from the transformation from adakitic granites to arc granites and from the ancient lower crust to the juvenile lower crust during the Early Cretaceous provided abundant fluids and material sources for mineralization. Moreover, the detachment faults formed by the rapid magmatic uplift and the extensional tectonism created favorable temperature and pressure conditions and space for fluid accumulation and gold precipitation and mineralization.
Global energy structure is experiencing the third transition from fossil energy to non-fossil energy, to solve future energy problems, cope with climate change, and achieve net-zero emissions targets by 2050. Hydrogen is considered to be the most potential clean energy in this century under the background of carbon neutrality. At present, the industrial methods for producing hydrogen are mainly by steam-hydrocarbon (such as coal and natural gas) reforming and by electrolysis of water, while the exploration and development of natural hydrogen had just started. According to this literature review: (1) Natural hydrogen can be divided into three categories, including free hydrogen, hydrogen in inclusions and dissolved hydrogen; (2) natural hydrogen could be mainly from abiotic origins such as by deep-seated hydrogen generation, water-rock reaction or water radiolysis; (3) natural hydrogen is widely distributed and presents great potential, and the potential natural hydrogen sources excluding deep source of hydrogen is about (254±91)×109 m3/a according to a latest estimate; (4) at present, natural hydrogen has been mined in Mali, and the exploration and development of natural hydrogen has also been carried out in Australia, Brazil, the United States and some European countries, to find many favorable areas and test some technical methods for natural hydrogen exploration. Natural hydrogen is expected to be an important part of hydrogen energy production in the future energy pattern. Based on a thorough literature review, this study introduced the origin, classification, and global discovery of natural hydrogen, as well as summarized the current global status and discussed the possibility of natural hydrogen exploration and development, aiming to provide reference for the future natural hydrogen exploration and development.
China is rich in abundant lithium resources characterized by considerable reserves and a concentrated distribution of metallogenic zones or belts, with proven reserves of 4046.8×103 t (calculated based on Li2O) by 2021. China is also a big consumer of lithium. By 2019, China’s lithium consumption in the battery sector alone had reached 99×103 t, with an average annual growth rate of nearly 26%. China has become the world’s largest importer of lithium resources, showing a severely unbalanced relationship between supply and demand for lithium resources. Therefore, there is an urgent need for the prospecting, exploitation, and study of lithium resources in China. This study collected, organized, and summarized the data on the major lithium deposits in China, analyzed and compared the spatial-temporal distribution patterns, geological characteristics, and metallogenic regularity of these lithium deposits, and summarized the prospecting and research achievements over the last decade. The major lithium deposits in China are distributed in provinces and regions such as Qinghai, Jiangxi, Sichuan, Tibet, and Xinjiang. These deposits are mostly small in scale. According to different genetic types, this study divided lithium deposits into granitic pegmatite type, granite type, saline lake brine type, underground brine type, and sedimentary type, as well as new types including hot spring type and magmatic-hydrothermal type, and summarized the characteristics and key metallogenic factors of these different types of deposits. Sixteen metallogenic prospect areas of lithium deposits were delineated according to the deposit types and the distribution patterns of metallogenic belts. The paper introduced the research progress in major metallogenic models and lithium extraction techniques made over the past decade. Based on the comprehensive analysis of the prospecting potential of lithium deposits, the authors concluded that the future prospecting of lithium resources in China should focus on lithium metallogenic belts, the deep and peripheral areas of currently determined large-scale pegmatite-type lithium deposits, geophysical-geochemical anomalous areas with mineralization clues, and areas with developed large-scale low-grade associated granite-type and sedimentary lithium resources. The study aims to serve as a guide for the future prospecting of lithium deposits in China.