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2025, 50(8): 2925-2936.
doi: 10.3799/dqkx.2025.032
Abstract:
The Shizhushan deposit (70 millions tons of wollastonite) in Jiangxi is situated in the eastern section of the Qin-Hang metallogenic belt and is recognized as the largest wollastonite deposit in the world. Within this deposit, W-Sn-Cu-Mo polymetallic mineralization is present in the skarns located in the contact zone between the Mengshan granite and the surrounding carbonate rocks. However, research on the formation age and genesis of this mineralization is relatively limited. This paper conducts in situ U-Pb dating and trace element analyses of garnets from different generations to determine the age of formation of the polymetallic mineralized skarns. The findings aim to enhance the understanding of the deposit's genesis and provide further guidance for mineral exploration. Three types of garnets have developed in the skarn: the first type consists of reddish-brown garnet (Grt-1), the second type comprises dark-brown garnet (Grt-2), and the third type features yellowish-green garnet (Grt-3). All three types of garnet belong to the andradite to grossularite solid-solution series; however, Grt-1 and Grt-2 are relatively rich in iron, while Grt-3 is relatively rich in aluminum. The U-Pb ages of Grt-2 and Grt-3 are 234.7±1.6 Ma and 234.4±9.9 Ma, respectively, which align with the ages of the biotite monzogranite from the Mengshan complex, widely exposed in the mining area. This study indicates that both wollastonite mineralization and polymetallic mineralization in the Shizhushan deposit occurred during the Late Triassic and are closely associated with the intrusion of the Mengshan granite. In addition to wollastonite, the Shizhushan deposit also holds significant potential for W-Sn-Cu-Mo polymetallic mineralization.
The Shizhushan deposit (70 millions tons of wollastonite) in Jiangxi is situated in the eastern section of the Qin-Hang metallogenic belt and is recognized as the largest wollastonite deposit in the world. Within this deposit, W-Sn-Cu-Mo polymetallic mineralization is present in the skarns located in the contact zone between the Mengshan granite and the surrounding carbonate rocks. However, research on the formation age and genesis of this mineralization is relatively limited. This paper conducts in situ U-Pb dating and trace element analyses of garnets from different generations to determine the age of formation of the polymetallic mineralized skarns. The findings aim to enhance the understanding of the deposit's genesis and provide further guidance for mineral exploration. Three types of garnets have developed in the skarn: the first type consists of reddish-brown garnet (Grt-1), the second type comprises dark-brown garnet (Grt-2), and the third type features yellowish-green garnet (Grt-3). All three types of garnet belong to the andradite to grossularite solid-solution series; however, Grt-1 and Grt-2 are relatively rich in iron, while Grt-3 is relatively rich in aluminum. The U-Pb ages of Grt-2 and Grt-3 are 234.7±1.6 Ma and 234.4±9.9 Ma, respectively, which align with the ages of the biotite monzogranite from the Mengshan complex, widely exposed in the mining area. This study indicates that both wollastonite mineralization and polymetallic mineralization in the Shizhushan deposit occurred during the Late Triassic and are closely associated with the intrusion of the Mengshan granite. In addition to wollastonite, the Shizhushan deposit also holds significant potential for W-Sn-Cu-Mo polymetallic mineralization.
2025, 50(8): 2937-2955.
doi: 10.3799/dqkx.2025.031
Abstract:
The Bayan Obo deposit in China is endowed with the largest rare earth element resource in the world. The Wu dyke is one of the typical carbonatite dyke in the eastern part of the deposit, but itsrelevant age span is relatively large in previous studies. To solve the issue, we carried out a detailed petrographic analysis of sectionfull scan, TIMA (TESCAN Intergrated Mineral Analyzer)scan, and trace element. The U-Pb dating was then carried out on zircons in the thin section of the quartz conglomerate that from the wall rock of the Wucarbonatite dyke. Petrographic analysis reveals three types of zircon distribution in the quartz conglomerate: most zircons are distributed in the contact area between quartz and orthoclase, and are accompanied by aegirine and albite in the surrounding areas; Some zircons are distributed in pure quartz, but some of them are surrounded by aegirine and albite particles; A small amount of zircon is distributed in orthoclase, and there are alsoamounts of albite and aegirine around zircon. The zircons in the quartz conglomerate have two main age peaks of ~2.5 Ga and ~1.9 Ga, and secondary age peak of ~2.3 Ga. The minimum zircon age of 1 844±18 Ma may represent the biggestsedimentary age of the Dulahala Formation in the Bayan Obo Group; all three types of zircons contain ages of 1.8~2.5 Ga.The Wucarbonatite dyke was formed at 1.4~1.3 Ga, and new zircons crystallized from the carbonatite magma when the dykewas emplaced, which is approximately coeval with the world-wide rifting events at this time that are associated with the final breakup of the Columbia supercontinent.Studies on the zircon ages of the Wucarbonatite dyke and wall rock show that the carbonatite dykeis contaminated with a large number of basement zircons. During the ~0.4 Ga period, the margins of some zircon in the Wucarbonatite dyke and in the Bayan Obo deposit were regrown, and some zircon cores were metasomatized.The ~0.2 Ga zircons from carbonatitethat around the Bayan Obo deposit maybeformed by hydrothermal fluids and/or reactions involving zircon and dolomite during contact metamorphism resulting from hydrothermal input from emplacement of the Permian granitoids.
The Bayan Obo deposit in China is endowed with the largest rare earth element resource in the world. The Wu dyke is one of the typical carbonatite dyke in the eastern part of the deposit, but itsrelevant age span is relatively large in previous studies. To solve the issue, we carried out a detailed petrographic analysis of sectionfull scan, TIMA (TESCAN Intergrated Mineral Analyzer)scan, and trace element. The U-Pb dating was then carried out on zircons in the thin section of the quartz conglomerate that from the wall rock of the Wucarbonatite dyke. Petrographic analysis reveals three types of zircon distribution in the quartz conglomerate: most zircons are distributed in the contact area between quartz and orthoclase, and are accompanied by aegirine and albite in the surrounding areas; Some zircons are distributed in pure quartz, but some of them are surrounded by aegirine and albite particles; A small amount of zircon is distributed in orthoclase, and there are alsoamounts of albite and aegirine around zircon. The zircons in the quartz conglomerate have two main age peaks of ~2.5 Ga and ~1.9 Ga, and secondary age peak of ~2.3 Ga. The minimum zircon age of 1 844±18 Ma may represent the biggestsedimentary age of the Dulahala Formation in the Bayan Obo Group; all three types of zircons contain ages of 1.8~2.5 Ga.The Wucarbonatite dyke was formed at 1.4~1.3 Ga, and new zircons crystallized from the carbonatite magma when the dykewas emplaced, which is approximately coeval with the world-wide rifting events at this time that are associated with the final breakup of the Columbia supercontinent.Studies on the zircon ages of the Wucarbonatite dyke and wall rock show that the carbonatite dykeis contaminated with a large number of basement zircons. During the ~0.4 Ga period, the margins of some zircon in the Wucarbonatite dyke and in the Bayan Obo deposit were regrown, and some zircon cores were metasomatized.The ~0.2 Ga zircons from carbonatitethat around the Bayan Obo deposit maybeformed by hydrothermal fluids and/or reactions involving zircon and dolomite during contact metamorphism resulting from hydrothermal input from emplacement of the Permian granitoids.
2025, 50(8): 2956-2976.
doi: 10.3799/dqkx.2025.039
Abstract:
Boninite is a special type of magnesium-iron volcanic rock, primarily formed in unique geological environments associated with plate subduction. It serves as a direct geological record of the subduction initiation. The phenocryst are mainly olivine and pyroxene, with no plagioclase. Boninite is characterized by high Mg and Si, but lower Ti content. They are also and enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), but depleted in high field strength elements (HFSEs) and medium rare earth elements (MREEs). Typicalboninite exhibits a distinctive "U"-shaped rare earth element (REE) distribution pattern.The unique chemical composition of boninite reflects its uniquemantle melting conditions, such as high temperature, low pressure, and relatively high water content.Primarymagma was generated throughre-melting processes in the mantle source, which has already undergone partial melting before. This unique melting process provides crucial insights into mantle source composition, degree of melting, and the role of fluids in mantle melting and the initiation of subduction.In this review, we discuss the mineralogy, geochemical characteristics, and petrogenetic mechanisms of subduction-related boninite, emphasizing its significance in geodynamics and magma evolution processes. Finally, we also summarized the current research issuesand potential future directions in boninite studies.
Boninite is a special type of magnesium-iron volcanic rock, primarily formed in unique geological environments associated with plate subduction. It serves as a direct geological record of the subduction initiation. The phenocryst are mainly olivine and pyroxene, with no plagioclase. Boninite is characterized by high Mg and Si, but lower Ti content. They are also and enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), but depleted in high field strength elements (HFSEs) and medium rare earth elements (MREEs). Typicalboninite exhibits a distinctive "U"-shaped rare earth element (REE) distribution pattern.The unique chemical composition of boninite reflects its uniquemantle melting conditions, such as high temperature, low pressure, and relatively high water content.Primarymagma was generated throughre-melting processes in the mantle source, which has already undergone partial melting before. This unique melting process provides crucial insights into mantle source composition, degree of melting, and the role of fluids in mantle melting and the initiation of subduction.In this review, we discuss the mineralogy, geochemical characteristics, and petrogenetic mechanisms of subduction-related boninite, emphasizing its significance in geodynamics and magma evolution processes. Finally, we also summarized the current research issuesand potential future directions in boninite studies.
2025, 50(8): 2977-2992.
doi: 10.3799/dqkx.2025.050
Abstract:
The Shuikoujing alkaline complex, the largest basic⁃ultrabasic complex exposed in the southern Panxi Rift.Previous studies suggest that the complex is closely related to the Late Permian Emeishan Large Igneous Province (ELIP) magmatic activity, but precise geochronological constraints have been lacking, which has hindered the understanding of the genesis, evolution, and tectono⁃dynamic background of the alkaline complex in the southern Panxirift.In this study, based on detailed petrographic and geochemical investigations, using LA⁃(MC)⁃ICP⁃MS analytical techniques to conduct U⁃Pb dating, trace element composition, and Sr isotopic analysis on apatite from various lithologies. These analyses aim to explore the genesis, evolution, and the associated tectono⁃dynamic background of the complex. The results show that the U⁃Pb ages of apatite from the gabbro and pyroxene diorite are 263±11 Ma and 262.8±6.4 Ma, The in situ Sr isotope composition of apatite is uniform (0.704 1~0.704 5) and exhibits typical mantle⁃derived characteristics. Suggesting that the formation of the primary magma is closely related to the activity of the ELIP, originating from low⁃degree partial melting of the lithospheric mantle in an intraplate extensional setting, and subsequently underwent rapid magmatic differentiation and evolution. Additionally, these alkaline complexes in the southern Panxi Rift are inferred to be products of the initial magmatic evolution of the ELIP.
The Shuikoujing alkaline complex, the largest basic⁃ultrabasic complex exposed in the southern Panxi Rift.Previous studies suggest that the complex is closely related to the Late Permian Emeishan Large Igneous Province (ELIP) magmatic activity, but precise geochronological constraints have been lacking, which has hindered the understanding of the genesis, evolution, and tectono⁃dynamic background of the alkaline complex in the southern Panxirift.In this study, based on detailed petrographic and geochemical investigations, using LA⁃(MC)⁃ICP⁃MS analytical techniques to conduct U⁃Pb dating, trace element composition, and Sr isotopic analysis on apatite from various lithologies. These analyses aim to explore the genesis, evolution, and the associated tectono⁃dynamic background of the complex. The results show that the U⁃Pb ages of apatite from the gabbro and pyroxene diorite are 263±11 Ma and 262.8±6.4 Ma, The in situ Sr isotope composition of apatite is uniform (0.704 1~0.704 5) and exhibits typical mantle⁃derived characteristics. Suggesting that the formation of the primary magma is closely related to the activity of the ELIP, originating from low⁃degree partial melting of the lithospheric mantle in an intraplate extensional setting, and subsequently underwent rapid magmatic differentiation and evolution. Additionally, these alkaline complexes in the southern Panxi Rift are inferred to be products of the initial magmatic evolution of the ELIP.
2025, 50(8): 2993-3012.
doi: 10.3799/dqkx.2025.068
Abstract:
The sodalite group minerals (SGM), including sodalite, haüyne, nosean, and related species, are aluminium silicate minerals that typically crystallize in alkaline⁃peralkaline rocks and are enriched in volatile elements such as sulfur (S) and chlorine (Cl). Despite their geochemical significance, research on SGM remains limited, particularly regarding their textural characteristics and geochemical compositions, which has hindered a comprehensive understanding of their classification and formation mechanisms. A detailed comparative study of the petrography and geochemistry of SGM samples was conducted, focusing on specimens from the Pinghe Complex (Sichuan Province, China), Niangniangshan Complex (Jiangsu Province, China), and Jebel Dumbier Complex (Sudan). This analysis was complemented by incorporating global SGM datasets to enhance the scope and robustness of the findings. A novel classification scheme for SGM species is proposed, based on the SO42-/X ratios (where X represents the anion content in atoms per formula unit, apfu) and X values. This framework distinguishes sodalite, nosean, and haüyne along a continuum of geochemical evolution. From sodalite to nosean and finally to haüyne, the ratios of Rb/Sr, Ba/Sr, Be/Sr, and B/Sr decrease progressively as Sr content increases. Conversely, total rare earth element (REE) concentrations and the degree of differentiation between light rare earth elements (LREE) and heavy rare earth elements (HREE) increase systematically. The S/Cl ratios in sodalite serve as a proxy for magma composition, while variations in Cl and S compositions reflect changes in melt volatile content during magmatic evolution. The clathrate texture observed in haüyne and the patchy texture in nosean are interpreted as resulting from mineral inclusions and solid exsolution processes, respectively. This study advances the understanding of SGM formation mechanisms and provides a refined framework for their classification, emphasizing the interplay between volatile elements, textural features, and geochemical evolution.
The sodalite group minerals (SGM), including sodalite, haüyne, nosean, and related species, are aluminium silicate minerals that typically crystallize in alkaline⁃peralkaline rocks and are enriched in volatile elements such as sulfur (S) and chlorine (Cl). Despite their geochemical significance, research on SGM remains limited, particularly regarding their textural characteristics and geochemical compositions, which has hindered a comprehensive understanding of their classification and formation mechanisms. A detailed comparative study of the petrography and geochemistry of SGM samples was conducted, focusing on specimens from the Pinghe Complex (Sichuan Province, China), Niangniangshan Complex (Jiangsu Province, China), and Jebel Dumbier Complex (Sudan). This analysis was complemented by incorporating global SGM datasets to enhance the scope and robustness of the findings. A novel classification scheme for SGM species is proposed, based on the SO42-/X ratios (where X represents the anion content in atoms per formula unit, apfu) and X values. This framework distinguishes sodalite, nosean, and haüyne along a continuum of geochemical evolution. From sodalite to nosean and finally to haüyne, the ratios of Rb/Sr, Ba/Sr, Be/Sr, and B/Sr decrease progressively as Sr content increases. Conversely, total rare earth element (REE) concentrations and the degree of differentiation between light rare earth elements (LREE) and heavy rare earth elements (HREE) increase systematically. The S/Cl ratios in sodalite serve as a proxy for magma composition, while variations in Cl and S compositions reflect changes in melt volatile content during magmatic evolution. The clathrate texture observed in haüyne and the patchy texture in nosean are interpreted as resulting from mineral inclusions and solid exsolution processes, respectively. This study advances the understanding of SGM formation mechanisms and provides a refined framework for their classification, emphasizing the interplay between volatile elements, textural features, and geochemical evolution.
2025, 50(8): 3013-3033.
doi: 10.3799/dqkx.2024.131
Abstract:
There are abundant Paleozoic intermediate⁃acid intrusive rocks in the Xiemisitai area, West Junggar, which is a hotspot for the study of crustal accretion of the Central Asian Orogenic Belt. In this study, detailed petrology, geochemistry, zircon U⁃Pb geochronology and Hf isotopic composition analysis were conducted for the intrusive rocks in the Wushijiagayiti gold deposit area in the western section of Xiemisitai. The results show that the intrusive rocks mainly consist of monzonites and quartz monzonites, with zircon U⁃Pb ages ranging from 429 to 424 Ma, εHf(t) values ranging from +11.7 to +15.2, and Hf isotope model ages of tDM2 of ca. 560 Ma. The monzonites and quartz monzonites have similar geochemical characteristics belonging to high⁃K calc⁃alkaline to shoshonitic series and are enriched in Rb, K, Zr and Hf, depleted Nb, Ta, P and Ti. All of them are typical of I⁃type granitoids and show continental arcaffinity. According to comprehensive research, it is inferred that the intermediate⁃acid intrusive rocks in the western section of the Xiemisitai area were derived from partial melting of young mafic lower crust in a volcanic arc setting during the northward subduction of the Junggar⁃Balkhash Ocean in the early Paleozoic. They recorded the transformation from a basaltic intra⁃oceanic arc to a continental arc during crustal growth.
There are abundant Paleozoic intermediate⁃acid intrusive rocks in the Xiemisitai area, West Junggar, which is a hotspot for the study of crustal accretion of the Central Asian Orogenic Belt. In this study, detailed petrology, geochemistry, zircon U⁃Pb geochronology and Hf isotopic composition analysis were conducted for the intrusive rocks in the Wushijiagayiti gold deposit area in the western section of Xiemisitai. The results show that the intrusive rocks mainly consist of monzonites and quartz monzonites, with zircon U⁃Pb ages ranging from 429 to 424 Ma, εHf(t) values ranging from +11.7 to +15.2, and Hf isotope model ages of tDM2 of ca. 560 Ma. The monzonites and quartz monzonites have similar geochemical characteristics belonging to high⁃K calc⁃alkaline to shoshonitic series and are enriched in Rb, K, Zr and Hf, depleted Nb, Ta, P and Ti. All of them are typical of I⁃type granitoids and show continental arcaffinity. According to comprehensive research, it is inferred that the intermediate⁃acid intrusive rocks in the western section of the Xiemisitai area were derived from partial melting of young mafic lower crust in a volcanic arc setting during the northward subduction of the Junggar⁃Balkhash Ocean in the early Paleozoic. They recorded the transformation from a basaltic intra⁃oceanic arc to a continental arc during crustal growth.
2025, 50(8): 3034-3051.
doi: 10.3799/dqkx.2025.023
Abstract:
The kinematic characteristics and dynamic mechanisms of key faults in the Yinggehai Basin and the Red River Fault Zone remain controversial. This study applies stratigraphic backstripping and balanced cross⁃section restoration to quantify subsidence and extensional rates of major faults in the Yinggehai Basin across different geological periods, aiming to clarify the tectonic activity of the Red River Fault Zone and the basin's evolutionary history.Results show that between 30 and 21 Ma, strike⁃slip faulting was primarily concentrated along the Song Lo Fault, while horizontal extension remained relatively minor. During this period, significant extensional deformation was localized in the Chay Fault zone. The main subsidence center was located in the Hanoi Depression, especially in the overlap zone of the Chay Fault, Thai Binh Fault, and east⁃west trending fault systems. From 21 to 15.5 Ma, tectonic inversion occurred in the northern basin, with the most intense compressional uplift centered on the Lingao Uplift. Concurrently, the Song Lo, Yingdong, and Dongfang Faults experienced varying degrees of tectonic inversion.The tectonic behavior of the Song Lo Fault mirrors that of the Red River Fault Zone, with the Yingdong and Dongfang Faults acting as southern extensions of the Song Lo Fault within the Yinggehai Basin. The escape tectonics of the Indochina Block was marked by substantial regional extension, with strike⁃slip deformation occurring along boundary faults on the eastern margin of the Yinggehai Basin, while extensional tectonics was widespread both within and around the basin. The observed tectonic inversion is closely linked to the reduction of left⁃lateral shear along onshore faults and the cessation of rotational motion of the Indochina Block.
The kinematic characteristics and dynamic mechanisms of key faults in the Yinggehai Basin and the Red River Fault Zone remain controversial. This study applies stratigraphic backstripping and balanced cross⁃section restoration to quantify subsidence and extensional rates of major faults in the Yinggehai Basin across different geological periods, aiming to clarify the tectonic activity of the Red River Fault Zone and the basin's evolutionary history.Results show that between 30 and 21 Ma, strike⁃slip faulting was primarily concentrated along the Song Lo Fault, while horizontal extension remained relatively minor. During this period, significant extensional deformation was localized in the Chay Fault zone. The main subsidence center was located in the Hanoi Depression, especially in the overlap zone of the Chay Fault, Thai Binh Fault, and east⁃west trending fault systems. From 21 to 15.5 Ma, tectonic inversion occurred in the northern basin, with the most intense compressional uplift centered on the Lingao Uplift. Concurrently, the Song Lo, Yingdong, and Dongfang Faults experienced varying degrees of tectonic inversion.The tectonic behavior of the Song Lo Fault mirrors that of the Red River Fault Zone, with the Yingdong and Dongfang Faults acting as southern extensions of the Song Lo Fault within the Yinggehai Basin. The escape tectonics of the Indochina Block was marked by substantial regional extension, with strike⁃slip deformation occurring along boundary faults on the eastern margin of the Yinggehai Basin, while extensional tectonics was widespread both within and around the basin. The observed tectonic inversion is closely linked to the reduction of left⁃lateral shear along onshore faults and the cessation of rotational motion of the Indochina Block.
2025, 50(8): 3052-3069.
doi: 10.3799/dqkx.2025.065
Abstract:
The Jiali Fault Zone is one of the major active tectonic structures along the southeastern margin of the Tibetan Plateau, playing a crucial role in regional seismicity and geomorphic evolution. This study systematically analyzes the tectonic activity of the Yiong-Zayu segment of the Jiali Fault Zone by integrating high-resolution remote sensing imagery, DEM data, field investigations, and focal mechanism solutions.The results indicate that the Jiali Fault Zone has exhibited weak tectonic activity since the Quaternary, with no significant evidence of right-lateral strike-slip motion. Instead, localized NW- and nearly E-W-trending normal faulting has been observed along certain segments, and seismic activity is predominantly characterized by local normal-faulting earthquakes. GPS velocity analysis reveals that the fault exhibits low horizontal slip rates, with deformation primarily characterized by extension, suggesting that it does not function as a major boundary fault.By integrating previous studies, we further infer that the formation of local normal faults is primarily influenced by localized shear stress or post-glacial rebound. Moreover, the kinematic model of southeastern Tibet is more consistent with a clockwise rotational extrusion mechanism.
The Jiali Fault Zone is one of the major active tectonic structures along the southeastern margin of the Tibetan Plateau, playing a crucial role in regional seismicity and geomorphic evolution. This study systematically analyzes the tectonic activity of the Yiong-Zayu segment of the Jiali Fault Zone by integrating high-resolution remote sensing imagery, DEM data, field investigations, and focal mechanism solutions.The results indicate that the Jiali Fault Zone has exhibited weak tectonic activity since the Quaternary, with no significant evidence of right-lateral strike-slip motion. Instead, localized NW- and nearly E-W-trending normal faulting has been observed along certain segments, and seismic activity is predominantly characterized by local normal-faulting earthquakes. GPS velocity analysis reveals that the fault exhibits low horizontal slip rates, with deformation primarily characterized by extension, suggesting that it does not function as a major boundary fault.By integrating previous studies, we further infer that the formation of local normal faults is primarily influenced by localized shear stress or post-glacial rebound. Moreover, the kinematic model of southeastern Tibet is more consistent with a clockwise rotational extrusion mechanism.
2025, 50(8): 3070-3084.
doi: 10.3799/dqkx.2025.064
Abstract:
The Madagascar Plateau (MADP), as a product of the separation of the Gondwana continent, exhibits unique topographic and geophysical characteristics. Through the interpretation and analysis of deep reflection seismic section A-A' across the MADP region, combined with gravity and magnetic anomaly data, the geological properties, crustal structure and sedimentary stratigraphic framework of the MADP are deeply studied, and the tectonic evolution process of lithosphere extension and rupture in the southern continental margin of Madagascar is clarified.Based on gravity and seismic data analysis, the MADP can be subdivided into the thinned continental crust in the north, the oceanic-continental transition zone (OCT) in the mid, and the thickened oceanic crust in the south. After undergoing rifting at 133 Ma, the southern continental margin of Madagascar experienced extension and rupture at 120 Ma, leading to the formation of a magmatic passive continental margin. Subsequently, influenced by the Marion hotspot (90–50 Ma), the continental and oceanic crust underwent further thickening due to magmatic activity, ultimately resulting in the present-day Madagascar Passive Margin (MADP). This research enhances our understanding of the development and evolution of MADP and has significant practical implications for determining seafloor high terrain attributes in the southwest Indian Ocean.
The Madagascar Plateau (MADP), as a product of the separation of the Gondwana continent, exhibits unique topographic and geophysical characteristics. Through the interpretation and analysis of deep reflection seismic section A-A' across the MADP region, combined with gravity and magnetic anomaly data, the geological properties, crustal structure and sedimentary stratigraphic framework of the MADP are deeply studied, and the tectonic evolution process of lithosphere extension and rupture in the southern continental margin of Madagascar is clarified.Based on gravity and seismic data analysis, the MADP can be subdivided into the thinned continental crust in the north, the oceanic-continental transition zone (OCT) in the mid, and the thickened oceanic crust in the south. After undergoing rifting at 133 Ma, the southern continental margin of Madagascar experienced extension and rupture at 120 Ma, leading to the formation of a magmatic passive continental margin. Subsequently, influenced by the Marion hotspot (90–50 Ma), the continental and oceanic crust underwent further thickening due to magmatic activity, ultimately resulting in the present-day Madagascar Passive Margin (MADP). This research enhances our understanding of the development and evolution of MADP and has significant practical implications for determining seafloor high terrain attributes in the southwest Indian Ocean.
2025, 50(8): 3085-3116.
doi: 10.3799/dqkx.2025.060
Abstract:
The deep carbon cycle significantly influences atmospheric CO2 concentrations, playing a critical role in global climate change and Earth's habitability. At convergent plate margins, surface carbon undergoes deep cycling through plate subduction via a series of processes such as metamorphic dehydration and/or partial melting, crust-mantle interactions, and magmatism. This paper presents a systematical review on the carbon reservoirs of the mantle and crust, the decarbonation mechanisms in subducting slabs, carbon sequestration during crust-mantle interactions, and the role of magmatic activity at convergent plate margins in deep carbon cycling and carbon release. It also outlines the footprints of deep carbon cycling in oceanic subduction zones and continental collision zones, along with the factors affecting carbon release, sequestration, or migration in various processes.
The deep carbon cycle significantly influences atmospheric CO2 concentrations, playing a critical role in global climate change and Earth's habitability. At convergent plate margins, surface carbon undergoes deep cycling through plate subduction via a series of processes such as metamorphic dehydration and/or partial melting, crust-mantle interactions, and magmatism. This paper presents a systematical review on the carbon reservoirs of the mantle and crust, the decarbonation mechanisms in subducting slabs, carbon sequestration during crust-mantle interactions, and the role of magmatic activity at convergent plate margins in deep carbon cycling and carbon release. It also outlines the footprints of deep carbon cycling in oceanic subduction zones and continental collision zones, along with the factors affecting carbon release, sequestration, or migration in various processes.
2025, 50(8): 3117-3131.
doi: 10.3799/dqkx.2025.093
Abstract:
With the continuous improvement of urbanization levels in China and the ongoing expansion of urban scales, the construction of major city clusters is becoming more mature. However, the pressure on urban development space and ecological environment is increasingly prominent, posing severe challenges to urban geological safety and the living environment. Therefore, there is an urgent need to conduct systematic research to ensure the quality of life for residents and social stability. This paper applies earth system science thinking and, based on explaining the universality of the layered structure and its feedback interactions, systematically analyzes the intrinsic relationship between the various layered structures of basins and urban geological safety. This includes the basement structural layer, the cover layer structure, the hydrological cycle layer, the underground space layer, and the surface engineering layer. It thoroughly examines the types of urban geological safety risks and their hazards under the dynamic influences of each layer, ultimately revealing the internal link between the interrelationships and feedback mechanisms of basin layers and urban geological safety risks. Specifically: Basement structural zone→Disaster-prone structural environment→Regional instability risk; Cap rock structure zone→Disaster-prone key layer zone→Localized cluster disaster risk; Hydrological cycle zone→Disaster-prone hydrological conditions→Urban ground subsidence risk; Subsurface space zone→Disaster-prone interaction zone →Surrounding rock deformation risk; Ground engineering zone→Disaster-prone clustered space →Shallow surface disaster risks. The interrelation and interaction between the layers, as well as the feedback effects, are crucial for urban geological safety early warning and risk prevention and control. These insights provide new perspectives for urban geological safety risk prevention, supporting the implementation of national strategies such as Safe China and Beautiful China.
With the continuous improvement of urbanization levels in China and the ongoing expansion of urban scales, the construction of major city clusters is becoming more mature. However, the pressure on urban development space and ecological environment is increasingly prominent, posing severe challenges to urban geological safety and the living environment. Therefore, there is an urgent need to conduct systematic research to ensure the quality of life for residents and social stability. This paper applies earth system science thinking and, based on explaining the universality of the layered structure and its feedback interactions, systematically analyzes the intrinsic relationship between the various layered structures of basins and urban geological safety. This includes the basement structural layer, the cover layer structure, the hydrological cycle layer, the underground space layer, and the surface engineering layer. It thoroughly examines the types of urban geological safety risks and their hazards under the dynamic influences of each layer, ultimately revealing the internal link between the interrelationships and feedback mechanisms of basin layers and urban geological safety risks. Specifically: Basement structural zone→Disaster-prone structural environment→Regional instability risk; Cap rock structure zone→Disaster-prone key layer zone→Localized cluster disaster risk; Hydrological cycle zone→Disaster-prone hydrological conditions→Urban ground subsidence risk; Subsurface space zone→Disaster-prone interaction zone →Surrounding rock deformation risk; Ground engineering zone→Disaster-prone clustered space →Shallow surface disaster risks. The interrelation and interaction between the layers, as well as the feedback effects, are crucial for urban geological safety early warning and risk prevention and control. These insights provide new perspectives for urban geological safety risk prevention, supporting the implementation of national strategies such as Safe China and Beautiful China.
2025, 50(8): 3132-3143.
doi: 10.3799/dqkx.2025.041
Abstract:
The identification of glacial lakes is a prerequisite for understanding their response to climate change and assessing potential risks of glacial lake outburst floods (GLOFs). Although remote sensing technology enables continuous monitoring and assessment of global glacial lake evolution, accurately and reliably extracting glacial lakes in complex plateau terrain regions remains challenging. This study proposes an intelligent glacial lake identification method for complex plateau terrain based on multi-source remote sensing data and an improved Mask R-CNN deep learning model. Building upon the original Mask R-CNN framework, we introduce attention mechanisms at three key components: the high-level features (Conv4 and Conv5) of the ResNet-50 backbone network, each feature map in the Feature Pyramid Network (FPN), and the Mask Head. Utilizing a multi-band dataset composed of Sentinel-2 high-resolution imagery, ALOS-DEM, and Normalized Difference Water Index (NDWI) data, we conducted tests in Nyingchi City, southeastern Tibetan Plateau. Comparative analyses were performed between the enhanced Mask R-CNN model and three other models (U-Net, SegNet, and DeepLab V3) for glacial lake identification. Results demonstrate that the improved Mask R-CNN achieves superior accuracy, with precision, recall, and accuracy values reaching 91.25%, 93.69%, and 92.89% respectively. The enhanced model effectively mitigates interference from mountain shadows, lake turbidity, and freeze-thaw conditions on glacial lake identification while significantly improving detection efficiency for small glacial lakes. This research provides a reliable solution for glacial lake identification in complex plateau terrain regions and establishes a novel framework combining deep learning with multi-source remote sensing data for intelligent glacial lake extraction, offering new possibilities for related studies.
The identification of glacial lakes is a prerequisite for understanding their response to climate change and assessing potential risks of glacial lake outburst floods (GLOFs). Although remote sensing technology enables continuous monitoring and assessment of global glacial lake evolution, accurately and reliably extracting glacial lakes in complex plateau terrain regions remains challenging. This study proposes an intelligent glacial lake identification method for complex plateau terrain based on multi-source remote sensing data and an improved Mask R-CNN deep learning model. Building upon the original Mask R-CNN framework, we introduce attention mechanisms at three key components: the high-level features (Conv4 and Conv5) of the ResNet-50 backbone network, each feature map in the Feature Pyramid Network (FPN), and the Mask Head. Utilizing a multi-band dataset composed of Sentinel-2 high-resolution imagery, ALOS-DEM, and Normalized Difference Water Index (NDWI) data, we conducted tests in Nyingchi City, southeastern Tibetan Plateau. Comparative analyses were performed between the enhanced Mask R-CNN model and three other models (U-Net, SegNet, and DeepLab V3) for glacial lake identification. Results demonstrate that the improved Mask R-CNN achieves superior accuracy, with precision, recall, and accuracy values reaching 91.25%, 93.69%, and 92.89% respectively. The enhanced model effectively mitigates interference from mountain shadows, lake turbidity, and freeze-thaw conditions on glacial lake identification while significantly improving detection efficiency for small glacial lakes. This research provides a reliable solution for glacial lake identification in complex plateau terrain regions and establishes a novel framework combining deep learning with multi-source remote sensing data for intelligent glacial lake extraction, offering new possibilities for related studies.
2025, 50(8): 3144-3152.
doi: 10.3799/dqkx.2025.061
Abstract:
Black soil in northeastern China is an important agricultural resource but has been increasingly degraded due to long-term development. The use of satellite remote sensing technology to retrieve the organic carbon content in black soil offers technical support for the protection and sustainable use. However, satellite hyperspectral data suffer from low spatial resolution, and the retrieval accuracy for organic carbon content remains limited in fine-scaled study sites. To address these challenges, this study utilized UAV-based hyperspectral data and soil geochemical data instead. We proposed and compared four models based on one-dimensional convolutional neural networks (1DCNN)-MDS-1DCNN, LLE-1DCNN, PLSR-1DCNN, and KPCA-1DCNN, for organic carbon content retrieval using the Wudalianchi region in Heilongjiang Province as a case study. The results show that the LLE-1DCNN model outperforms the others, achieving an R2 of 0.806 and an RMSE of 0.572% on the validation set. This approach offers promising potential for accurately retrieving organic carbon content in black soil and supporting its conservation and management.
Black soil in northeastern China is an important agricultural resource but has been increasingly degraded due to long-term development. The use of satellite remote sensing technology to retrieve the organic carbon content in black soil offers technical support for the protection and sustainable use. However, satellite hyperspectral data suffer from low spatial resolution, and the retrieval accuracy for organic carbon content remains limited in fine-scaled study sites. To address these challenges, this study utilized UAV-based hyperspectral data and soil geochemical data instead. We proposed and compared four models based on one-dimensional convolutional neural networks (1DCNN)-MDS-1DCNN, LLE-1DCNN, PLSR-1DCNN, and KPCA-1DCNN, for organic carbon content retrieval using the Wudalianchi region in Heilongjiang Province as a case study. The results show that the LLE-1DCNN model outperforms the others, achieving an R2 of 0.806 and an RMSE of 0.572% on the validation set. This approach offers promising potential for accurately retrieving organic carbon content in black soil and supporting its conservation and management.
2025, 50(8): 3153-3166.
doi: 10.3799/dqkx.2025.056
Abstract:
Large landslides are typically characterized by the multi-sliding zones structure, influenced by engineering geological conditions.However, the impact of the soil arch effect on multi-sliding zones landslide is often overlooked in studies of anti-slide piles reinforcement.Therefore, numerical simulations of multi-sliding zones landslide-anti-sliding piles system under thrust loading were conducted. These simulations investigated the effects of pile spacing and embedment depth on the soil arching effect across different motion modes and evaluated the reinforcement effectiveness under various design parameters.The results show that: (1) During landslide movement in multi-sliding zones, the stress around the pile exhibits a bidirectional, multi-level soil arch distribution along the depth, manifesting as the phenomenon of "soil arch behind pile-soil arch in front of the pile-soil arch behind pile". (2) As the pile spacing decreases from six times to two times the pile diameter, the end-bearing soil arch effect at various depths becomes more pronounced, thereby improving the reinforcement effect. Conversely, when the pile spacing increases from two times to six times, the frictional soil arch between the piles gradually becomes the dominant anti-slide mechanism, diminishing the reinforcement effectiveness.(3) Changes in embedding depth do not alter the type of soil arch at different depths but affect the strength of the soil arch.(4) When shallow sliding dominates, reducing pile spacing enhances the reinforcement effect of anti-slide piles; when deep sliding dominates, increasing the embedment depth improves the reinforcement effect.
Large landslides are typically characterized by the multi-sliding zones structure, influenced by engineering geological conditions.However, the impact of the soil arch effect on multi-sliding zones landslide is often overlooked in studies of anti-slide piles reinforcement.Therefore, numerical simulations of multi-sliding zones landslide-anti-sliding piles system under thrust loading were conducted. These simulations investigated the effects of pile spacing and embedment depth on the soil arching effect across different motion modes and evaluated the reinforcement effectiveness under various design parameters.The results show that: (1) During landslide movement in multi-sliding zones, the stress around the pile exhibits a bidirectional, multi-level soil arch distribution along the depth, manifesting as the phenomenon of "soil arch behind pile-soil arch in front of the pile-soil arch behind pile". (2) As the pile spacing decreases from six times to two times the pile diameter, the end-bearing soil arch effect at various depths becomes more pronounced, thereby improving the reinforcement effect. Conversely, when the pile spacing increases from two times to six times, the frictional soil arch between the piles gradually becomes the dominant anti-slide mechanism, diminishing the reinforcement effectiveness.(3) Changes in embedding depth do not alter the type of soil arch at different depths but affect the strength of the soil arch.(4) When shallow sliding dominates, reducing pile spacing enhances the reinforcement effect of anti-slide piles; when deep sliding dominates, increasing the embedment depth improves the reinforcement effect.
2025, 50(8): 3167-3181.
doi: 10.3799/dqkx.2025.048
Abstract:
This study aims to develop a methodology for implicit 3D geological modeling under the constraint of limited exploration data availability. Taking Lazigougold deposit as an example, we generate virtual grooving by distance weighting method based on the original grooving sampling data, and use the original grooving data to train and evaluate three machine learning models, namely K-nearest neighbor, random forest and gradient elevator, and select the random forest model with the best prediction performance to discriminate and predict the lithology of virtual grooving. Virtual encryption of groove data is realized by machine learning method, which provides a large number of sample data for implicit 3D modeling. On this basis, the orebody model and Au element grade numerical model of Lazigou gold mine were constructed in implicit modeling software using the original groove and virtual groove data. Five prospecting targets have been delimited, which have been proved reliable by engineering. The implicit 3D modeling based on machine learning can make full use of the known data to predict the unknown region and provide sufficient samples for the implicit 3D modeling, which is conducive to the construction of a higher precision geological model under the existing exploration engineering conditions, and then provide a basis for the deep edge prospecting prediction.
This study aims to develop a methodology for implicit 3D geological modeling under the constraint of limited exploration data availability. Taking Lazigougold deposit as an example, we generate virtual grooving by distance weighting method based on the original grooving sampling data, and use the original grooving data to train and evaluate three machine learning models, namely K-nearest neighbor, random forest and gradient elevator, and select the random forest model with the best prediction performance to discriminate and predict the lithology of virtual grooving. Virtual encryption of groove data is realized by machine learning method, which provides a large number of sample data for implicit 3D modeling. On this basis, the orebody model and Au element grade numerical model of Lazigou gold mine were constructed in implicit modeling software using the original groove and virtual groove data. Five prospecting targets have been delimited, which have been proved reliable by engineering. The implicit 3D modeling based on machine learning can make full use of the known data to predict the unknown region and provide sufficient samples for the implicit 3D modeling, which is conducive to the construction of a higher precision geological model under the existing exploration engineering conditions, and then provide a basis for the deep edge prospecting prediction.
2025, 50(8): 3182-3198.
doi: 10.3799/dqkx.2025.067
Abstract:
Coseismic landslide mapping plays a crucial role in emergency response and disaster assessment. To improve landslide identification, this paper proposes a novel and enhanced model, MultiU-EGANet. The model is built upon the U-Net architecture as the baseline, with the introduction of the MultiRes module to extract feature information across multiple scales. Additionally, the Edge-Guided Attention (EGA) module is incorporated to enhance the delineation of landslide boundaries using the Laplace operator, thereby improving the segmentation accuracy at the boundaries. A composite loss function, combining Dice loss and Focal loss, is designed to further enhance the model's robustness. Using landslide data from the Jiuzhaigou area, experimental results demonstrate that the proposed model significantly improves landslide identification accuracy compared to the baseline model. Furthermore, comparative experiments conducted with landslide data from Hokkaido show that the proposed method outperforms existing models in landslide identification tasks, with F1 scores increasing by 33.31%, 5.45%, 2.31%, and 2.18%, respectively. These results validate the effectiveness of the proposed method for coseismic landslide identification.
Coseismic landslide mapping plays a crucial role in emergency response and disaster assessment. To improve landslide identification, this paper proposes a novel and enhanced model, MultiU-EGANet. The model is built upon the U-Net architecture as the baseline, with the introduction of the MultiRes module to extract feature information across multiple scales. Additionally, the Edge-Guided Attention (EGA) module is incorporated to enhance the delineation of landslide boundaries using the Laplace operator, thereby improving the segmentation accuracy at the boundaries. A composite loss function, combining Dice loss and Focal loss, is designed to further enhance the model's robustness. Using landslide data from the Jiuzhaigou area, experimental results demonstrate that the proposed model significantly improves landslide identification accuracy compared to the baseline model. Furthermore, comparative experiments conducted with landslide data from Hokkaido show that the proposed method outperforms existing models in landslide identification tasks, with F1 scores increasing by 33.31%, 5.45%, 2.31%, and 2.18%, respectively. These results validate the effectiveness of the proposed method for coseismic landslide identification.
2025, 50(8): 3199-3212.
doi: 10.3799/dqkx.2023.190
Abstract:
A unique "fan delta-braided river delta" composite sedimentary system is developed in Enping Formation, Huizhou 26 depression, the Pearl River Mouth Basin, and typical "fan braid" system transformation has occurred in different sedimentary evolution stages of different structures. The reservoir physical conditions before and after the transformation are quite different, so it is urgent to carry out in-depth research. Based on three-dimensional seismic data and core testing data, this article comprehensively analyzes the differential distribution characteristics and main controlling factors of the "fan-braid" composite system reservoir in the Enping Formation of Huizhou 26 Depression, and clarifies the "fan-braid" evolution relationship of the "southern fan northern braid, early fan late braid" in the region; At the same time, the three main controlling factors for the development of high-quality reservoirs in this composite system, namely "superior facies-transformation-volcano", have been deeply revealed. Among them, high-quality sedimentary facies are the material basis for the development of high-quality reservoirs, transformation of multi-level fault stage transportation, and lake wave washing under the background of ancient uplift are the key to improving reservoir physical properties, while differential diagenetic evolution of volcanic materials plays a regulatory role in reservoir physical properties. Relatively speaking, the overall physical properties of the braided river delta facies reservoirs in the Enping Formation of Huizhou 26 Depression are good, but it is still necessary to search for favorable reservoir development zones that are less affected by volcanic materials above the lower burial depth limit; And for the subfacies of the fan delta front, it is necessary to strengthen the research on the transformation effect and select the reservoirs under strong transformation effect.
A unique "fan delta-braided river delta" composite sedimentary system is developed in Enping Formation, Huizhou 26 depression, the Pearl River Mouth Basin, and typical "fan braid" system transformation has occurred in different sedimentary evolution stages of different structures. The reservoir physical conditions before and after the transformation are quite different, so it is urgent to carry out in-depth research. Based on three-dimensional seismic data and core testing data, this article comprehensively analyzes the differential distribution characteristics and main controlling factors of the "fan-braid" composite system reservoir in the Enping Formation of Huizhou 26 Depression, and clarifies the "fan-braid" evolution relationship of the "southern fan northern braid, early fan late braid" in the region; At the same time, the three main controlling factors for the development of high-quality reservoirs in this composite system, namely "superior facies-transformation-volcano", have been deeply revealed. Among them, high-quality sedimentary facies are the material basis for the development of high-quality reservoirs, transformation of multi-level fault stage transportation, and lake wave washing under the background of ancient uplift are the key to improving reservoir physical properties, while differential diagenetic evolution of volcanic materials plays a regulatory role in reservoir physical properties. Relatively speaking, the overall physical properties of the braided river delta facies reservoirs in the Enping Formation of Huizhou 26 Depression are good, but it is still necessary to search for favorable reservoir development zones that are less affected by volcanic materials above the lower burial depth limit; And for the subfacies of the fan delta front, it is necessary to strengthen the research on the transformation effect and select the reservoirs under strong transformation effect.
2025, 50(8): 3213-3224.
doi: 10.3799/dqkx.2025.045
Abstract:
The pull apart basin, also known as the diamond basin, typically forms in strong strike-slip tectonic setting. However, Huizhou Sag of Pearl River Mouth Basin developed the distinctive diamond-shaped graben during the Eocene rifting period under tensional-shear setting. Base on three-dimensional seismic and drilling data, along with regional tectonic context, This study investigates the structural characteristics, genesis mechanism, and oil and gas accumulation of tensional-shear rhomb graben. Huizhou Sag developed three types of primary faults: NE-SW trending extensional faults, nearly E-W trending shear-tensional faults, and NW-SE trending tensional-shear faults. Three types of major faults activated differently during the deposition of the Wenchang Formation and jointly controlled the four evolution stages of the transtensional rhombohedral graben in the Huixi area: the development phase of the compound half graben, the embryonic stage of the rhomb graben, the expansion phase of the rhomb graben, and the definitive stage of the rhomb graben. The Huizhou Beiweitan hidden fault was formed and developed in Indosinian-Yanshanian period, and its left-lateral activation area basically covered the whole Huixi area in the Himalayan period. Controlled by the NW-SE trending extensional setting of the first episode of the Zhuqiong Movement Ⅰ and the sinistral activation of Huizhou-Beiweitan hidden fault, Huixi sag developed a basin style of tensional-shearrhomb graben. At the same time, the development and evolution of diamond shaped graben control the development scale of source rocks, the formation of large trap groups, fault sealing, oil and gas migration. The NW-SE trending Paleogene trap group has great potential for oil and gas exploration.
The pull apart basin, also known as the diamond basin, typically forms in strong strike-slip tectonic setting. However, Huizhou Sag of Pearl River Mouth Basin developed the distinctive diamond-shaped graben during the Eocene rifting period under tensional-shear setting. Base on three-dimensional seismic and drilling data, along with regional tectonic context, This study investigates the structural characteristics, genesis mechanism, and oil and gas accumulation of tensional-shear rhomb graben. Huizhou Sag developed three types of primary faults: NE-SW trending extensional faults, nearly E-W trending shear-tensional faults, and NW-SE trending tensional-shear faults. Three types of major faults activated differently during the deposition of the Wenchang Formation and jointly controlled the four evolution stages of the transtensional rhombohedral graben in the Huixi area: the development phase of the compound half graben, the embryonic stage of the rhomb graben, the expansion phase of the rhomb graben, and the definitive stage of the rhomb graben. The Huizhou Beiweitan hidden fault was formed and developed in Indosinian-Yanshanian period, and its left-lateral activation area basically covered the whole Huixi area in the Himalayan period. Controlled by the NW-SE trending extensional setting of the first episode of the Zhuqiong Movement Ⅰ and the sinistral activation of Huizhou-Beiweitan hidden fault, Huixi sag developed a basin style of tensional-shearrhomb graben. At the same time, the development and evolution of diamond shaped graben control the development scale of source rocks, the formation of large trap groups, fault sealing, oil and gas migration. The NW-SE trending Paleogene trap group has great potential for oil and gas exploration.
2025, 50(8): 3225-3240.
doi: 10.3799/dqkx.2025.047
Abstract:
Since the discovery of dolomite 233 years ago, it is still the forefront of basic research. Mg isotope, as a key isotope in the formation of dolomite, has become a new hotspot in the study of dolomite. The research progress on the characteristics of magnesium and magnesium isotopes in geological storage, fractionation, magnesium cycling and biogenic magnesium isotopes are briefly reviewed. The characteristics of Mg isotope, fluid direction and stratigraphic sequence in dolomite cores collected from Xisha Islands since Neogene reef were studied. Taking the study of deep-deep and ultra-deep dolomite magnesium isotope reservoirs for oil and gas exploration in sedimentary basins in western China as an example, this paper briefly introduces the evaluation results of magnesium isotope study. Progress has been made in the study of magnesium isotopes in the fields of paleo-ocean reconstruction, global continents, ocean and earth interior magnesium storage and magnesium cycling, which has promoted the discussion of frontier issues of dolomite, and strengthened the understanding of dolomite formation and mechanism.
Since the discovery of dolomite 233 years ago, it is still the forefront of basic research. Mg isotope, as a key isotope in the formation of dolomite, has become a new hotspot in the study of dolomite. The research progress on the characteristics of magnesium and magnesium isotopes in geological storage, fractionation, magnesium cycling and biogenic magnesium isotopes are briefly reviewed. The characteristics of Mg isotope, fluid direction and stratigraphic sequence in dolomite cores collected from Xisha Islands since Neogene reef were studied. Taking the study of deep-deep and ultra-deep dolomite magnesium isotope reservoirs for oil and gas exploration in sedimentary basins in western China as an example, this paper briefly introduces the evaluation results of magnesium isotope study. Progress has been made in the study of magnesium isotopes in the fields of paleo-ocean reconstruction, global continents, ocean and earth interior magnesium storage and magnesium cycling, which has promoted the discussion of frontier issues of dolomite, and strengthened the understanding of dolomite formation and mechanism.
2025, 50(8): 3241-3269.
doi: 10.3799/dqkx.2025.057
Abstract:
Fujian Province is one of the most important geothermal anomaly areas in China. It is of great significance for the scientific utilization of geothermal resources to reveal the formation mechanisms of geothermal system in the region. The changes in hydrochemical formation and water-rock interaction mechanism of geothermal fluidsin each hydrogeochemical zonewas clarified based on the implication of hydrochemical characteristics of 208 geothermal water samples and the machine learning methods of self-organizing map-K-means (SOM-KM) clustering. The results show that the water types of geothermal fluids from the uplifted mountainous recharge areas to the low-lying valleys and deep basin axis evolved from HCO3-Ca and HCO3-Na·Ca to HCO3·SO4-Naand HCO3-Na in each intact groundwater system in inland areas. While from the central mountainous areas to the eastern volcano-graben basin and coastal plain, the water types of geothermal fluids evolved from HCO3-Ca, HCO3-Na·Ca to HCO3·SO4-Na and HCO3-Na, and then Cl-Na·Ca, Cl-Na type. The SOM-KM analysis identified the spatial distribution of low-enthalpy and low-salinity shallow circulating geothermal water, high-enthalpy and P-F-SiO2 enriched deep circulating geothermal water, and deep circulation geothermal water with seawater mixing at the provincial scale effectively. Among them, the low-enthalpy shallow circulating geothermal water was significantly affected by the mixing of surface water and shallow groundwater, and mainly distributed along the steam systems of northwestern uplifted mountain region and the carbonate-clastic sedimentary basins of southeastern region. The hydrochemistry formation of high-enthalpy deep circulating geothermal water was significantly influenced by the upwelling mixing of endogenous water in igneous rocks, deep-seated faults, and ancient sealed fluids in volcanic edifice, and mainly distributed at the intersection of regional northwestern water-conducting faults with the northeastern thermal-conducting faults and the radioactive faults of the circular volcanic apparatus in eastern volcanic depression zone. The deep circulation geothermal fluid affected by seawater recharge undergone the first mixing process with the deep high-salinity seawater and the second mixing process with shallow cold water during the upwelling stage. The long-term supply end member of hydrochemistry in regional intrusive-volcanic geothermal reservoir is plagioclase, and the reservoir temperature indicated by mineral hydrothermal alteration is concentrated in the range of 100-150 ℃. The geothermal fluid tended to evolve towards HCO3-Na water with high pH, low-Na concentration and high-Ca concentration under the constraints of super saturation precipitation of calcite - carbonate buffer equilibrium system due to the preferential dissolution of olivine, pyroxene, and anorthite in the plagioclase. The geothermal system in the bulk horizons is turned out to be deep-circulation hydrothermal systems without magmatic heat source from the hydrogeochemical evidence.
Fujian Province is one of the most important geothermal anomaly areas in China. It is of great significance for the scientific utilization of geothermal resources to reveal the formation mechanisms of geothermal system in the region. The changes in hydrochemical formation and water-rock interaction mechanism of geothermal fluidsin each hydrogeochemical zonewas clarified based on the implication of hydrochemical characteristics of 208 geothermal water samples and the machine learning methods of self-organizing map-K-means (SOM-KM) clustering. The results show that the water types of geothermal fluids from the uplifted mountainous recharge areas to the low-lying valleys and deep basin axis evolved from HCO3-Ca and HCO3-Na·Ca to HCO3·SO4-Naand HCO3-Na in each intact groundwater system in inland areas. While from the central mountainous areas to the eastern volcano-graben basin and coastal plain, the water types of geothermal fluids evolved from HCO3-Ca, HCO3-Na·Ca to HCO3·SO4-Na and HCO3-Na, and then Cl-Na·Ca, Cl-Na type. The SOM-KM analysis identified the spatial distribution of low-enthalpy and low-salinity shallow circulating geothermal water, high-enthalpy and P-F-SiO2 enriched deep circulating geothermal water, and deep circulation geothermal water with seawater mixing at the provincial scale effectively. Among them, the low-enthalpy shallow circulating geothermal water was significantly affected by the mixing of surface water and shallow groundwater, and mainly distributed along the steam systems of northwestern uplifted mountain region and the carbonate-clastic sedimentary basins of southeastern region. The hydrochemistry formation of high-enthalpy deep circulating geothermal water was significantly influenced by the upwelling mixing of endogenous water in igneous rocks, deep-seated faults, and ancient sealed fluids in volcanic edifice, and mainly distributed at the intersection of regional northwestern water-conducting faults with the northeastern thermal-conducting faults and the radioactive faults of the circular volcanic apparatus in eastern volcanic depression zone. The deep circulation geothermal fluid affected by seawater recharge undergone the first mixing process with the deep high-salinity seawater and the second mixing process with shallow cold water during the upwelling stage. The long-term supply end member of hydrochemistry in regional intrusive-volcanic geothermal reservoir is plagioclase, and the reservoir temperature indicated by mineral hydrothermal alteration is concentrated in the range of 100-150 ℃. The geothermal fluid tended to evolve towards HCO3-Na water with high pH, low-Na concentration and high-Ca concentration under the constraints of super saturation precipitation of calcite - carbonate buffer equilibrium system due to the preferential dissolution of olivine, pyroxene, and anorthite in the plagioclase. The geothermal system in the bulk horizons is turned out to be deep-circulation hydrothermal systems without magmatic heat source from the hydrogeochemical evidence.
2025, 50(8): 3270-3283.
doi: 10.3799/dqkx.2025.103
Abstract:
Destructive earthquakes and other natural disasters not only cause deterioration of the regional ecological environment, but also lead to soil erosion and local poverty, but also have a more direct impact on the loss of people's lives and property, as well as the destruction and deformation of ground buildings such as residential buildings. The Surface deformation characteristics, ground subsidence, and building collapse caused by the Ms 6.8 earthquake occurred in Dingri County, southern Tibet on January 7, 2025 were comprehensively analyzed through field investigations. The vertical displacement intensity along the Dingmu Co fault decreases from vertical displacement of over 185 cm at an altitude of over 5 500 meters in the north to vertical displacement of less than 120 cm at an altitude of over 4 200 meters in the east of Dingmu Co; The northern section has a westward drop, which is due to the overall descent of the upper plate of the Dingmu Co fault, with some sections descending in a stepped manner, resulting in steep slopes of up to 3 meters for ice water sediments and slope foot alluvial deposits in the ice eroded U-shaped valley; Occasionally, dry cow manure, Permafrost bulge, and huge ice debris being left displaced, indicating that this earthquake also had obvious strike slip characteristics. A Surface deformation with a north-south extension and an east-west width of up to 50 meters appeared in the alluvial deposits of the eastern Pleistocene in Dingmu Co, characterized by a central collapse and overall westward subsidence. The steep slope of the tensile rupture generally does not exceed 120 cm, and up to 50 cm squeezing uplift and seismic bulges are also developed at the leading edge of the tensile rupture, near the local section of Dingmu Co. The villages of Jiweng and Gurong, located in the center of the surface fissure, were the most severely affected by the Dingri earthquake. Except for a few cement and brick houses, most of the houses collapsed, making them the most severely affected villages in this earthquake. Based on the analysis of regional geological background, the Dingri earthquake is a shallow source destructive earthquake controlled by extensional structures. The upwelling of mantle thermal material in the Cenozoic era activated extensional structures represented by the north-south Dingmu Co strike-slip normal fault and the nearly east-west Tibetan southern detachment system, releasing energy at the intersection of these extensional structures and causing earthquakes.
Destructive earthquakes and other natural disasters not only cause deterioration of the regional ecological environment, but also lead to soil erosion and local poverty, but also have a more direct impact on the loss of people's lives and property, as well as the destruction and deformation of ground buildings such as residential buildings. The Surface deformation characteristics, ground subsidence, and building collapse caused by the Ms 6.8 earthquake occurred in Dingri County, southern Tibet on January 7, 2025 were comprehensively analyzed through field investigations. The vertical displacement intensity along the Dingmu Co fault decreases from vertical displacement of over 185 cm at an altitude of over 5 500 meters in the north to vertical displacement of less than 120 cm at an altitude of over 4 200 meters in the east of Dingmu Co; The northern section has a westward drop, which is due to the overall descent of the upper plate of the Dingmu Co fault, with some sections descending in a stepped manner, resulting in steep slopes of up to 3 meters for ice water sediments and slope foot alluvial deposits in the ice eroded U-shaped valley; Occasionally, dry cow manure, Permafrost bulge, and huge ice debris being left displaced, indicating that this earthquake also had obvious strike slip characteristics. A Surface deformation with a north-south extension and an east-west width of up to 50 meters appeared in the alluvial deposits of the eastern Pleistocene in Dingmu Co, characterized by a central collapse and overall westward subsidence. The steep slope of the tensile rupture generally does not exceed 120 cm, and up to 50 cm squeezing uplift and seismic bulges are also developed at the leading edge of the tensile rupture, near the local section of Dingmu Co. The villages of Jiweng and Gurong, located in the center of the surface fissure, were the most severely affected by the Dingri earthquake. Except for a few cement and brick houses, most of the houses collapsed, making them the most severely affected villages in this earthquake. Based on the analysis of regional geological background, the Dingri earthquake is a shallow source destructive earthquake controlled by extensional structures. The upwelling of mantle thermal material in the Cenozoic era activated extensional structures represented by the north-south Dingmu Co strike-slip normal fault and the nearly east-west Tibetan southern detachment system, releasing energy at the intersection of these extensional structures and causing earthquakes.
2025, 50(8): 3284-3300.
doi: 10.3799/dqkx.2025.081
Abstract:
High-precision coseismic surface deformation is a key parameter for understanding shallow fault rupture mechanisms and accurately assessing seismic hazard. For the first time, GaoFen-7 imagery and Digital Surface Model (DSM) differencing technique were employed to obtain high-resolution coseismic surface vertical deformation associated with the January 7, 2025 Dingri Ms6.8 earthquake in Tibet, China. The revealed surface trace of the seismogenic fault and vertical deformation characteristics coincide with the Dengmocuo Fault dominated by normal faulting, indicating that the earthquake was a normal-faulting event. This earthquake generated a 42-kilometer-long surface deformation zone, with distinct segmentation in both deformation amplitude, gradient and width related to fault geometric complexity and dynamic rupture process. The deformation zone is divided into three segments from north to south: the N22°E-trending Zhananla segment, the N160°E-trending Dengmocuo Lake segment, and the N25°E-trending Cuoguoxiang segment. Pronounced deformation occurred in the Zhananla segment, reaching a maximum vertical displacement of approximately 2.97±0.20 m meters. The surface deformation observed along the Dengmocuo Lake segment is the least pronounced, potentially attributable to a change in the fault's orientation.The width of the coseismic deformation zone on fault segments spans 100 to 150 meters, suggesting that the diffuse deformation occurring within a limited volume surrounding the faults may be overlooked or underestimated, so it is necessary to carry out high-precision continuous monitoring.
High-precision coseismic surface deformation is a key parameter for understanding shallow fault rupture mechanisms and accurately assessing seismic hazard. For the first time, GaoFen-7 imagery and Digital Surface Model (DSM) differencing technique were employed to obtain high-resolution coseismic surface vertical deformation associated with the January 7, 2025 Dingri Ms6.8 earthquake in Tibet, China. The revealed surface trace of the seismogenic fault and vertical deformation characteristics coincide with the Dengmocuo Fault dominated by normal faulting, indicating that the earthquake was a normal-faulting event. This earthquake generated a 42-kilometer-long surface deformation zone, with distinct segmentation in both deformation amplitude, gradient and width related to fault geometric complexity and dynamic rupture process. The deformation zone is divided into three segments from north to south: the N22°E-trending Zhananla segment, the N160°E-trending Dengmocuo Lake segment, and the N25°E-trending Cuoguoxiang segment. Pronounced deformation occurred in the Zhananla segment, reaching a maximum vertical displacement of approximately 2.97±0.20 m meters. The surface deformation observed along the Dengmocuo Lake segment is the least pronounced, potentially attributable to a change in the fault's orientation.The width of the coseismic deformation zone on fault segments spans 100 to 150 meters, suggesting that the diffuse deformation occurring within a limited volume surrounding the faults may be overlooked or underestimated, so it is necessary to carry out high-precision continuous monitoring.
2025, 50(8): 3301-3315.
doi: 10.3799/dqkx.2025.119
Abstract:
In order to study the Seismic damage mechanism.Based on the field investigation, it was found that the seismic damages of adobe-timber structures are collapse, partial collapse, cracking on walls, damage to timber parts, frame structure occured collapse, the damage to the beams and columns is rare and light, and the seismic damage mainly occurred in infilled walls.Masonry structures occured partial collapse, the joints of bottom frame structures were seriously damaged, shear damage to walls.The result shows that adobe-timber structures exist vertical rigidity irregular, plane rigidity irregular, poor integrity of wall, etc.Frame structures exit the construction quality problem like lack of tie bar, low reinforcement ratio in columns and poor quality of concrete.Masonry structures also exit construction quality problems, such as low mortar strength, lack of seismic measures, etc.At the end of this article, some suggestions about the buliding defects are provided in order to provide ideas for reinforcement and reconstruction.
In order to study the Seismic damage mechanism.Based on the field investigation, it was found that the seismic damages of adobe-timber structures are collapse, partial collapse, cracking on walls, damage to timber parts, frame structure occured collapse, the damage to the beams and columns is rare and light, and the seismic damage mainly occurred in infilled walls.Masonry structures occured partial collapse, the joints of bottom frame structures were seriously damaged, shear damage to walls.The result shows that adobe-timber structures exist vertical rigidity irregular, plane rigidity irregular, poor integrity of wall, etc.Frame structures exit the construction quality problem like lack of tie bar, low reinforcement ratio in columns and poor quality of concrete.Masonry structures also exit construction quality problems, such as low mortar strength, lack of seismic measures, etc.At the end of this article, some suggestions about the buliding defects are provided in order to provide ideas for reinforcement and reconstruction.
2021, 46(12): 4452-4469.
doi: 10.3799/dqkx.2021.117
2013, 38(3): 454-460.
doi: 10.3799/dqkx.2013.045
2014, 39(3): 261-270.
doi: 10.3799/dqkx.2014.025
2014, 39(3): 283-292.
doi: 10.3799/dqkx.2014.027
2015, 40(2): 206-233.
doi: 10.3799/dqkx.2015.016
