2024 Vol. 49, No. 11
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2024, 49(11): 3855-3878.
doi: 10.3799/dqkx.2024.104
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Abstract:
Anshan-Benxi (Anben) is located in the northeastern North China Craton and is well-known for the huge banded iron formation (BIF) and 3.8 Ga rocks. Its importance lies not only in the discovery of 3.8 Ga rocks, but also in the long-term history of Archean crustal formation and evolution from 3.8 to 2.5 Ga. 3.8 Ga rocks occur in ancient complexes in the Anshan area. So far, six complexes have been identified. They are mainly composed of trondhjemitic rocks with meta-gabbro-diorite and have similar rock assemblages and zircon age records of 3.8‒3.1 Ga, thus considered to be the different remnants of the same one large ancient complex. In addition to the complexes, other important geological bodies include the Paleoarchean Chentaigou supracrustal rocks and the late Neoarchean Anshan Group, the 3.3‒3.1 Ga Chentaigou granite, 3.1 Ga Lishan trondhjemite, 3.0 Ga Donganshan granite, 3.0‒2.95 Ga Tiejiashan-Gongchangling granite and 2.5 Ga Qidashan granite. Three tectonothermal events have been identified at 3.3 Ga, 3.1 Ga and 2.5 Ga. Granitoid magmatism evolved from trondhjemite to K-rich granite with the renewal of time. The total REE amounts and light to heavy REE differentiations of the rocks increased suddenly at 3.3 Ga. The trondhjemitic rocks are considered to be mainly derived from low-K iron-magnesian rocks, with some from TTG rocks, whereas the K-rich granites are from TTG and sedimentary rocks. According to whole-rock Nd and zircon Hf isotopic compositions, both mantle addition and intracrustal recycling played important roles in each magmatic period, with the latter becoming more and more important with time, but the late Neoarchean is also an important period of mantle addition. The following conclusions have been obtained. (1) 3.3 Ga is an important period in the continental formation and evolution of the Anben area, with the thickness and scale of continental crust increasing significantly; (2) a long-term crustally-derived magmatism occurred between 3.3 and 2.95 Ga, with the granites increasing with time in magmatic intensity and K2O contents. (3) the Anshan Group was deposited on the > 2.95 Ga ancient continental basement, and there was a "quiet period" of ~400 Ma (2.95‒2.55 Ga) between the formation of the ancient basement and the deposition of the Anshan Group. (4) The formation and evolution of the Archean basement in the Anben area can be divided into four stages: continental nucleus formation (> 3.3 Ga), ancient block formation (3.3‒2.95 Ga), quiet period (2.95‒2.55 Ga) and stabilization (2.55‒2.5 Ga).
Anshan-Benxi (Anben) is located in the northeastern North China Craton and is well-known for the huge banded iron formation (BIF) and 3.8 Ga rocks. Its importance lies not only in the discovery of 3.8 Ga rocks, but also in the long-term history of Archean crustal formation and evolution from 3.8 to 2.5 Ga. 3.8 Ga rocks occur in ancient complexes in the Anshan area. So far, six complexes have been identified. They are mainly composed of trondhjemitic rocks with meta-gabbro-diorite and have similar rock assemblages and zircon age records of 3.8‒3.1 Ga, thus considered to be the different remnants of the same one large ancient complex. In addition to the complexes, other important geological bodies include the Paleoarchean Chentaigou supracrustal rocks and the late Neoarchean Anshan Group, the 3.3‒3.1 Ga Chentaigou granite, 3.1 Ga Lishan trondhjemite, 3.0 Ga Donganshan granite, 3.0‒2.95 Ga Tiejiashan-Gongchangling granite and 2.5 Ga Qidashan granite. Three tectonothermal events have been identified at 3.3 Ga, 3.1 Ga and 2.5 Ga. Granitoid magmatism evolved from trondhjemite to K-rich granite with the renewal of time. The total REE amounts and light to heavy REE differentiations of the rocks increased suddenly at 3.3 Ga. The trondhjemitic rocks are considered to be mainly derived from low-K iron-magnesian rocks, with some from TTG rocks, whereas the K-rich granites are from TTG and sedimentary rocks. According to whole-rock Nd and zircon Hf isotopic compositions, both mantle addition and intracrustal recycling played important roles in each magmatic period, with the latter becoming more and more important with time, but the late Neoarchean is also an important period of mantle addition. The following conclusions have been obtained. (1) 3.3 Ga is an important period in the continental formation and evolution of the Anben area, with the thickness and scale of continental crust increasing significantly; (2) a long-term crustally-derived magmatism occurred between 3.3 and 2.95 Ga, with the granites increasing with time in magmatic intensity and K2O contents. (3) the Anshan Group was deposited on the > 2.95 Ga ancient continental basement, and there was a "quiet period" of ~400 Ma (2.95‒2.55 Ga) between the formation of the ancient basement and the deposition of the Anshan Group. (4) The formation and evolution of the Archean basement in the Anben area can be divided into four stages: continental nucleus formation (> 3.3 Ga), ancient block formation (3.3‒2.95 Ga), quiet period (2.95‒2.55 Ga) and stabilization (2.55‒2.5 Ga).
2024, 49(11): 3879-3889.
doi: 10.3799/dqkx.2024.101
Abstract:
The understanding of the origin of Earth's earliest crust is incomplete due to the limited rock record in the first billion-year of Earth's history. The short-lived isotope system, 146Sm-142Nd, taking advantage of its short half-life of 103 Ma, is especially effective in tracing the chemical differentiation of incompatible elements during the Hadean and thus constraining the origin of the first crust on Earth. Studies show that multiple mantle depletion events may have occurred on the early Earth that were likely caused by the formation of massive proto-crust. The massive proto-crust is not only the likely progenitor of the oldest preserved igneous rocks on Earth, but also has served as the nuclei for the formation of Neoarchean continent. Here in this review article, the isotopic systematics and the analytical methods of 146Sm-142Nd were reviewed, and the current models for the formation of Earth's earliest crust were discussed based on a compilation of 142Nd isotopic anomaly data of ancient samples from global Eoarchean terranes.
The understanding of the origin of Earth's earliest crust is incomplete due to the limited rock record in the first billion-year of Earth's history. The short-lived isotope system, 146Sm-142Nd, taking advantage of its short half-life of 103 Ma, is especially effective in tracing the chemical differentiation of incompatible elements during the Hadean and thus constraining the origin of the first crust on Earth. Studies show that multiple mantle depletion events may have occurred on the early Earth that were likely caused by the formation of massive proto-crust. The massive proto-crust is not only the likely progenitor of the oldest preserved igneous rocks on Earth, but also has served as the nuclei for the formation of Neoarchean continent. Here in this review article, the isotopic systematics and the analytical methods of 146Sm-142Nd were reviewed, and the current models for the formation of Earth's earliest crust were discussed based on a compilation of 142Nd isotopic anomaly data of ancient samples from global Eoarchean terranes.
2024, 49(11): 3890-3903.
doi: 10.3799/dqkx.2024.097
Abstract:
The new progresses in analytical methods of in situ S isotope measurement by using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and secondary ion mass spectrometry (SIMS) have been reviewed in this paper. The review is focused on the key technical difficulties, correction schemes of mass spectrum interference, and mass fractionation effects in the two instruments. As it suggested, both LA-MC-ICP-MS and SIMS can accurately determine the δ34S of various minerals, such as pyrite, chalcopyrite, sphalerite, galenite, pyrrhotite, pentlandite, molybdenite etc. The analytical accuracy is comparable to the traditional bulk analysis. The analytical precision (reproducibility) is ranges of from 0.17‰ to 0.45‰. There are a large number of reference materials of S isotope analysis in sulfides. However, the main reference materials are pyrite, chalcopyrite, pyrrhotite, and sphalerite. Other sulfides also lack the reference materials for microanalysis. It is suggested that improving the hardwares or key equipments, resolving the isotope fractionation and the matrix effect, developing the new sulfide reference materials will be the major development directions for the in situ S isotopic measurement by LA-MC-ICP-MS and SIMS.
The new progresses in analytical methods of in situ S isotope measurement by using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and secondary ion mass spectrometry (SIMS) have been reviewed in this paper. The review is focused on the key technical difficulties, correction schemes of mass spectrum interference, and mass fractionation effects in the two instruments. As it suggested, both LA-MC-ICP-MS and SIMS can accurately determine the δ34S of various minerals, such as pyrite, chalcopyrite, sphalerite, galenite, pyrrhotite, pentlandite, molybdenite etc. The analytical accuracy is comparable to the traditional bulk analysis. The analytical precision (reproducibility) is ranges of from 0.17‰ to 0.45‰. There are a large number of reference materials of S isotope analysis in sulfides. However, the main reference materials are pyrite, chalcopyrite, pyrrhotite, and sphalerite. Other sulfides also lack the reference materials for microanalysis. It is suggested that improving the hardwares or key equipments, resolving the isotope fractionation and the matrix effect, developing the new sulfide reference materials will be the major development directions for the in situ S isotopic measurement by LA-MC-ICP-MS and SIMS.
2024, 49(11): 3904-3916.
doi: 10.3799/dqkx.2023.136
Abstract:
It is still difficult to accurately correct the interferences of REE2+ in Sr isotopic analysis by LA-MC-ICP-MS. In this study, we corrected the interferences of REE2+ by RPSM (Routine Peak Stripping Method) combining use of an improved cup configuration of MC-ICP-MS allowing for synchronic detection of REE2+ signals. The effectiveness of IFCC (Improved Faraday Cup Configuration) was evaluated with respect to both the synchrony and the ratios of REE2+ signals. With IFCC, no decoupling of REE2+ signals was observed. This finding indicates that IFCC is well suited for RPSM to correct the interferences of REE2+. The ratios of REE2+ signals (r: 166, 168, 170Er2+/167Er2+和170, 172, 174, 176Yb2+/173Yb2+) are approximately equal to (r/R≈1) the natural isotopic abundant ratios of Er an Yb (R: 166, 168, 170Er/167Er和170, 172, 174, 176Yb/173Yb). This property cause IFCC to be well suited to correct interferences of REE2+ with the R and the measured signals of 167Er2+ and 173Yb2+. We also determined the Sr isotopic compositions of the Er and Yb-spiked 0.1 μg/g NBS987 Sr solutions by SN-MC-ICP-MS with IFCC, and the results attest that the interferences of REE2+ in the solutions with Sr/Er≥3 can be corrected using the RPSM (R as the interference correction factor), and those in the solutions with Sr/Er≥1 can be corrected using the EPSM (Enhanced Peak Stripping Method, measured r as the interference correction factor). Sr isotopic compositions of two rich-REE reference materials (Durango with Sr/Er=7.4, and UWA-1 with Sr/Er=2.8) were determined by LA-MC-ICP-MS with IFCC, and the determined 87Sr/86Sr of the two reference materials are 0.706 27±0.000 14 (2SD, n=19) and 0.704 76±0.000 19 (2SD, n=20), respectively, both of which agree with previously published values (determined by TIMS or MC-ICP-MS) within uncertainties.
It is still difficult to accurately correct the interferences of REE2+ in Sr isotopic analysis by LA-MC-ICP-MS. In this study, we corrected the interferences of REE2+ by RPSM (Routine Peak Stripping Method) combining use of an improved cup configuration of MC-ICP-MS allowing for synchronic detection of REE2+ signals. The effectiveness of IFCC (Improved Faraday Cup Configuration) was evaluated with respect to both the synchrony and the ratios of REE2+ signals. With IFCC, no decoupling of REE2+ signals was observed. This finding indicates that IFCC is well suited for RPSM to correct the interferences of REE2+. The ratios of REE2+ signals (r: 166, 168, 170Er2+/167Er2+和170, 172, 174, 176Yb2+/173Yb2+) are approximately equal to (r/R≈1) the natural isotopic abundant ratios of Er an Yb (R: 166, 168, 170Er/167Er和170, 172, 174, 176Yb/173Yb). This property cause IFCC to be well suited to correct interferences of REE2+ with the R and the measured signals of 167Er2+ and 173Yb2+. We also determined the Sr isotopic compositions of the Er and Yb-spiked 0.1 μg/g NBS987 Sr solutions by SN-MC-ICP-MS with IFCC, and the results attest that the interferences of REE2+ in the solutions with Sr/Er≥3 can be corrected using the RPSM (R as the interference correction factor), and those in the solutions with Sr/Er≥1 can be corrected using the EPSM (Enhanced Peak Stripping Method, measured r as the interference correction factor). Sr isotopic compositions of two rich-REE reference materials (Durango with Sr/Er=7.4, and UWA-1 with Sr/Er=2.8) were determined by LA-MC-ICP-MS with IFCC, and the determined 87Sr/86Sr of the two reference materials are 0.706 27±0.000 14 (2SD, n=19) and 0.704 76±0.000 19 (2SD, n=20), respectively, both of which agree with previously published values (determined by TIMS or MC-ICP-MS) within uncertainties.
2024, 49(11): 3917-3929.
doi: 10.3799/dqkx.2024.121
Abstract:
Arsenic poisoning caused by high-arsenic groundwater represents a significant threat to human health. The arsenic methylation process, which converts highly toxic inorganic arsenic into less toxic methylated arsenic species, has the potential to mitigate the environmental risk of arsenic contamination and reduce its toxicity to humans. This process may provide an effective approach to managing arsenic pollution in groundwater. However, current research predominantly focuses on the migration of inorganic arsenic, with limited understanding of the key processes and controlling factors that govern the enrichment of methylated arsenic. In this study, it analyzed shallow groundwater from the Jianghan plain, located along the Yangtze and Han rivers, using inorganic carbon isotope tracing and EEMs of dissolved organic matter. The aim of this study is to elucidate the organic matter degradation pathways that regulate the enrichment of methylated arsenic and to identify the key biogeochemical processes involved. It found that methylated arsenic concentrations in the Jianghan plain ranged from < 0.01 to 444 μg/L, with an average concentration of 30 μg/L. The processes controlling methylated arsenic enrichment differed significantly between groundwater from the Yangtze River and the Han River. Along the Yangtze River, the degradation of high-molecular-weight aromatic organic compounds drives methanogenesis, which in turn promotes arsenic biomethylation and the subsequent enrichment of methylated arsenic in groundwater. Additionally, the sulfate reduction process, associated with the fermentation of organic matter, also supports arsenic biomethylation. In contrast, in the Han River region, the arsenic biomethylation process is primarily driven by the fermentation of small-molecule reactive organic matter.
Arsenic poisoning caused by high-arsenic groundwater represents a significant threat to human health. The arsenic methylation process, which converts highly toxic inorganic arsenic into less toxic methylated arsenic species, has the potential to mitigate the environmental risk of arsenic contamination and reduce its toxicity to humans. This process may provide an effective approach to managing arsenic pollution in groundwater. However, current research predominantly focuses on the migration of inorganic arsenic, with limited understanding of the key processes and controlling factors that govern the enrichment of methylated arsenic. In this study, it analyzed shallow groundwater from the Jianghan plain, located along the Yangtze and Han rivers, using inorganic carbon isotope tracing and EEMs of dissolved organic matter. The aim of this study is to elucidate the organic matter degradation pathways that regulate the enrichment of methylated arsenic and to identify the key biogeochemical processes involved. It found that methylated arsenic concentrations in the Jianghan plain ranged from < 0.01 to 444 μg/L, with an average concentration of 30 μg/L. The processes controlling methylated arsenic enrichment differed significantly between groundwater from the Yangtze River and the Han River. Along the Yangtze River, the degradation of high-molecular-weight aromatic organic compounds drives methanogenesis, which in turn promotes arsenic biomethylation and the subsequent enrichment of methylated arsenic in groundwater. Additionally, the sulfate reduction process, associated with the fermentation of organic matter, also supports arsenic biomethylation. In contrast, in the Han River region, the arsenic biomethylation process is primarily driven by the fermentation of small-molecule reactive organic matter.
2024, 49(11): 3930-3945.
doi: 10.3799/dqkx.2024.100
Abstract:
Post-collisional potassic magmas are commonly regarded as evidence for the recycling of subducted sediments in the lithospheric mantle of orogenic belts, with potassium isotope serving as an excellent tracer for these recycled sediments. This study takes the lamprophyres from the Sanjiang region as an example, conducting potassium isotope analysis based on major and trace elements and Sr-Nd-Pb isotopes, to explore the characteristics of the lithospheric mantle source in the Sanjiang region.This study reveals that the lamprophyres from four distinct regions-Jianchuan, Beiya, Yanyuan, and Yao'an-collectively represent the characteristics of the mantle source. These samples exhibit no association with weathering alteration, fractional crystallization, crustal contamination, and dynamic fractionation processes. Overall, compared to the mantle, the samples display slightly lighter potassium isotopic compositions from (-0.61±0.02)‰ to (-0.31±0.01)‰, suggesting a correlation with subducted sediment metasomatism rather than with fluids typically enriched in heavier potassium isotopes.Further simulations utilizing the Monte Carlo model for end-member mixing calculations indicate varying degrees of subducted sediment incorporation in the four regions, with the sediment proportion in the Yao'an area potentially reaching up to 10%. This conclusion further substantiates the efficacy of potassium isotope as a sensitive tracer, capable of effectively tracking the recycled subduction sediment components within the mantle.
Post-collisional potassic magmas are commonly regarded as evidence for the recycling of subducted sediments in the lithospheric mantle of orogenic belts, with potassium isotope serving as an excellent tracer for these recycled sediments. This study takes the lamprophyres from the Sanjiang region as an example, conducting potassium isotope analysis based on major and trace elements and Sr-Nd-Pb isotopes, to explore the characteristics of the lithospheric mantle source in the Sanjiang region.This study reveals that the lamprophyres from four distinct regions-Jianchuan, Beiya, Yanyuan, and Yao'an-collectively represent the characteristics of the mantle source. These samples exhibit no association with weathering alteration, fractional crystallization, crustal contamination, and dynamic fractionation processes. Overall, compared to the mantle, the samples display slightly lighter potassium isotopic compositions from (-0.61±0.02)‰ to (-0.31±0.01)‰, suggesting a correlation with subducted sediment metasomatism rather than with fluids typically enriched in heavier potassium isotopes.Further simulations utilizing the Monte Carlo model for end-member mixing calculations indicate varying degrees of subducted sediment incorporation in the four regions, with the sediment proportion in the Yao'an area potentially reaching up to 10%. This conclusion further substantiates the efficacy of potassium isotope as a sensitive tracer, capable of effectively tracking the recycled subduction sediment components within the mantle.
2024, 49(11): 3946-3959.
doi: 10.3799/dqkx.2024.093
Abstract:
To investigate how surface water-groundwater interactions influence the speciation and sources of nitrogen (N) in wetland-groundwater systems, this study focuses on the Honghu Lake wetland, and utilizing groundwater flow direction, hydrochemical methods and stable isotopes to demonstrate the speciation, sources and transformation of N in the wetland-groundwater system. The results indicate that nitrate and ammonium are the primary species of N in surface water and groundwater, respectively. Nitrate in surface water mainly originates from external river inputs, while ammonium in groundwater may result from organic matter degradation or autotrophic nitrate reduction to ammonium (DNRA), with the latter being the predominant source. Eutrophic lake water-groundwater interactions can introduce nitrate into groundwater and, under the influence of DNRA, create localized high ammonium groundwater. Therefore, surface water-groundwater interaction in wetlands is a significant driver affecting groundwater quality.
To investigate how surface water-groundwater interactions influence the speciation and sources of nitrogen (N) in wetland-groundwater systems, this study focuses on the Honghu Lake wetland, and utilizing groundwater flow direction, hydrochemical methods and stable isotopes to demonstrate the speciation, sources and transformation of N in the wetland-groundwater system. The results indicate that nitrate and ammonium are the primary species of N in surface water and groundwater, respectively. Nitrate in surface water mainly originates from external river inputs, while ammonium in groundwater may result from organic matter degradation or autotrophic nitrate reduction to ammonium (DNRA), with the latter being the predominant source. Eutrophic lake water-groundwater interactions can introduce nitrate into groundwater and, under the influence of DNRA, create localized high ammonium groundwater. Therefore, surface water-groundwater interaction in wetlands is a significant driver affecting groundwater quality.
2024, 49(11): 3960-3970.
doi: 10.3799/dqkx.2023.040
Abstract:
Eoarchean rocks are of great significance for understanding the formation and evolution of the earliest continental crust due to their scarcity. In this study, it reports zircon U-Pb ages of a newly recognized tonalitic gneiss and plagioclase-amphibolitic gneiss assemblage in the northern Dabie belt, which is named as the "Muzidian gneiss complex". The zircon dating results show that the ages of the plagioclase-amphibolitic schist and tonalitic gneiss in the Muzidian gneiss complex are (3 653±43) Ma and (3 701±29) Ma, respectively, which are the oldest rocks known in the Yangtze craton, indicating ancient basement rocks may exist beneath the craton. A comparative study with the basement rocks of the Kongling complex reveals that both the lithology and age of the Muzidian gneiss complex are distinct from those of the Kongling complex, indicating that they may represent independent microcontinental nucleus of the Yangtze craton.
Eoarchean rocks are of great significance for understanding the formation and evolution of the earliest continental crust due to their scarcity. In this study, it reports zircon U-Pb ages of a newly recognized tonalitic gneiss and plagioclase-amphibolitic gneiss assemblage in the northern Dabie belt, which is named as the "Muzidian gneiss complex". The zircon dating results show that the ages of the plagioclase-amphibolitic schist and tonalitic gneiss in the Muzidian gneiss complex are (3 653±43) Ma and (3 701±29) Ma, respectively, which are the oldest rocks known in the Yangtze craton, indicating ancient basement rocks may exist beneath the craton. A comparative study with the basement rocks of the Kongling complex reveals that both the lithology and age of the Muzidian gneiss complex are distinct from those of the Kongling complex, indicating that they may represent independent microcontinental nucleus of the Yangtze craton.
2024, 49(11): 3971-3994.
doi: 10.3799/dqkx.2024.116
Abstract:
The Nasarawa region in central Nigeria is a typical area with developed lithium-niobium-tantalum rare metal pegmatite veins. The Kama granitic pegmatite-type rare metal deposit, located in the central part of the Nigerian lithium-niobium-tantalum-tin polymetallic metallogenic belt, is a newly discovered large deposit mainly containing lithium with associated niobium and tantalum ores. To define its metallogenic age and explore the sources and evolution of its mineralization process, this paper conducts a study of petrology, mineralogy, zircon and cassiterite U-Pb geochronology, zircon trace elements, and Lu-Hf isotopes on the ore-bearing pegmatite veins The zircon U-Pb dating yields the ages of (577.3±2.5) Ma (n=18, MSWD=6.4), and the cassiterite U-Pb dating yields the ages of (582.6±8.6) Ma (n=25, MSWD=0.72), therefore the pegmatite of the Kama deposit is inferred to have formed between 577 and 583 Ma, with the main mineralization occurring in the late Neoproterozoic. Trace elementsgeochemical analyses indicate that the pegmatites in the study area were formed during subduction-collision processes, with their magma source primarily being metamorphic sedimentary rocks, originating from the continental crust. The magma evolution process may have involved fractional crystallization of minerals such as plagioclase, apatite, and zircon. The intense fractional crystallization evolution of the magma results in rocks with highly differentiated evolutionary characteristics. The Hf isotopic compositions of zircon, cassiterite and columbite-tantalite in pegmatite show that the εHf(t) value of zircon is between -20.6 and -19.0, and the TDM2 value is 2.7 Ga; The εHf(t) value of cassiterite is between -17.7 and -14.9, and the TDM2 value varies between 2.4 Ga and 2.6 Ga. The εHf(t) value of Columbite-tantalite is between -15.9 and -7.4, and the TDM2 values are between 2.0 Ga and 2.4 Ga, indicating that the parent melt of pegmatite mainly originated from the remelting of Neoarchean-Proterozoic basement rocks. The mineralization of rare metal pegmatite deposits in Nigeria is closely related to Gondwana orogeny, which corresponds to the post-collision extension period of Gondwana orogeny.
The Nasarawa region in central Nigeria is a typical area with developed lithium-niobium-tantalum rare metal pegmatite veins. The Kama granitic pegmatite-type rare metal deposit, located in the central part of the Nigerian lithium-niobium-tantalum-tin polymetallic metallogenic belt, is a newly discovered large deposit mainly containing lithium with associated niobium and tantalum ores. To define its metallogenic age and explore the sources and evolution of its mineralization process, this paper conducts a study of petrology, mineralogy, zircon and cassiterite U-Pb geochronology, zircon trace elements, and Lu-Hf isotopes on the ore-bearing pegmatite veins The zircon U-Pb dating yields the ages of (577.3±2.5) Ma (n=18, MSWD=6.4), and the cassiterite U-Pb dating yields the ages of (582.6±8.6) Ma (n=25, MSWD=0.72), therefore the pegmatite of the Kama deposit is inferred to have formed between 577 and 583 Ma, with the main mineralization occurring in the late Neoproterozoic. Trace elementsgeochemical analyses indicate that the pegmatites in the study area were formed during subduction-collision processes, with their magma source primarily being metamorphic sedimentary rocks, originating from the continental crust. The magma evolution process may have involved fractional crystallization of minerals such as plagioclase, apatite, and zircon. The intense fractional crystallization evolution of the magma results in rocks with highly differentiated evolutionary characteristics. The Hf isotopic compositions of zircon, cassiterite and columbite-tantalite in pegmatite show that the εHf(t) value of zircon is between -20.6 and -19.0, and the TDM2 value is 2.7 Ga; The εHf(t) value of cassiterite is between -17.7 and -14.9, and the TDM2 value varies between 2.4 Ga and 2.6 Ga. The εHf(t) value of Columbite-tantalite is between -15.9 and -7.4, and the TDM2 values are between 2.0 Ga and 2.4 Ga, indicating that the parent melt of pegmatite mainly originated from the remelting of Neoarchean-Proterozoic basement rocks. The mineralization of rare metal pegmatite deposits in Nigeria is closely related to Gondwana orogeny, which corresponds to the post-collision extension period of Gondwana orogeny.
2024, 49(11): 3995-4007.
doi: 10.3799/dqkx.2024.061
Abstract:
Fluctuations in phosphorus fluxes to and from the lake have a direct impact on the stability of river ecosystems. In the Dongting Lake area, where water quality fluctuates, the SWAT model was used to simulate the phosphorus inflow and outflow fluxes and to analyze the retention rate in each area. A coupled model was constructed based on hydrophysical processes, being trained by the results of the SWAT model and using the model to make scenario predictions of recent water quality in the lake area. The results showed that the inflow and outflow phosphorus fluxes in Dongting Lake showed obvious seasonal variations, with inorganic phosphorus being the main phosphorus format. From 2012 to 2021, the average TP inflow flux in Dongting Lake was 2.94×104 t/a, the average TP outflow flux was 3.34×104 t/a, and the average TP outflow concentration was 0.13 mg/L. Among the sub-basins, the Sankou area as the area with the largest contribution of phosphorus flux into the lake and the highest TP output concentration, should be emphasized to manage the phosphorus pollution in this area. The low TP retention rate in the Dongting Lake area may turn it into an important source of TP in the lower reaches of the Yangtze River. Coupled modeling is relatively precise for simulating the output process of river phosphorus fluxes, with all NSE values > 0.8, and all RMSE values are low at the RPE value at 10% level, which realizes the simulation modeling of the LSTM network instead of the large-scale distributed physical model.Based on the above model, the recent TP output concentration of Dongting Lake area was predicted according to the "Dongting Lake Water Environment Comprehensive Management Plan", and the scenario of controlling the TP concentration inflow into the lake in each area at 0.1 mg/L can realize the water environment planning objectives of the lake area.
Fluctuations in phosphorus fluxes to and from the lake have a direct impact on the stability of river ecosystems. In the Dongting Lake area, where water quality fluctuates, the SWAT model was used to simulate the phosphorus inflow and outflow fluxes and to analyze the retention rate in each area. A coupled model was constructed based on hydrophysical processes, being trained by the results of the SWAT model and using the model to make scenario predictions of recent water quality in the lake area. The results showed that the inflow and outflow phosphorus fluxes in Dongting Lake showed obvious seasonal variations, with inorganic phosphorus being the main phosphorus format. From 2012 to 2021, the average TP inflow flux in Dongting Lake was 2.94×104 t/a, the average TP outflow flux was 3.34×104 t/a, and the average TP outflow concentration was 0.13 mg/L. Among the sub-basins, the Sankou area as the area with the largest contribution of phosphorus flux into the lake and the highest TP output concentration, should be emphasized to manage the phosphorus pollution in this area. The low TP retention rate in the Dongting Lake area may turn it into an important source of TP in the lower reaches of the Yangtze River. Coupled modeling is relatively precise for simulating the output process of river phosphorus fluxes, with all NSE values > 0.8, and all RMSE values are low at the RPE value at 10% level, which realizes the simulation modeling of the LSTM network instead of the large-scale distributed physical model.Based on the above model, the recent TP output concentration of Dongting Lake area was predicted according to the "Dongting Lake Water Environment Comprehensive Management Plan", and the scenario of controlling the TP concentration inflow into the lake in each area at 0.1 mg/L can realize the water environment planning objectives of the lake area.
2024, 49(11): 4008-4021.
doi: 10.3799/dqkx.2023.152
Abstract:
Groundwater is the main or even the only source of drinking water in the eastern plain of Xinjiang. The pollution status of inorganic components in groundwater and their negative effects on human health are still unclear. The concentrations of common inorganic components in 183 groundwater samples were determined, and the spatial distribution characteristics of pollutants were revealed by GIS technology, positive matrix factorization (PMF) model was used for source apportionment, and the health risks of potential sources were quantified by coupling Monte Carlo simulation (MCS) and PMF based on USEPA health risk assessment model. The groundwater quality in the eastern plain of Xinjiang was mainly affected by SO42- and Cl-, and 30.60% and 17.49% of the groundwater exceeded the limit of national drinking water standard (250 mg·L-1), respectively, the high value points are concentrated in Santanghu Town of Balikun County, the southeast of Gaochang District and the east of Shanshan County. PMF analyzed six potential sources of inorganic components in groundwater, including leaching and evaporation concentration, aquifer lithology, agricultural activity, biogeochemical process, redox environment and geological environment background, the contribution rates were 82.43%, 7.64%, 6.87%, 1.96%, 0.80% and 0.30% respectively. The results of health risk assessment show that Cl- was the main inorganic pollutant harmful to human health, and the non-carcinogenic risk of adults and children could be neglected. The contribution rate of leaching and evaporation concentration to the non-carcinogenic risk of adults and children were more than 95.00%. Considering the safety of drinking water, the high value area of Cl- should be selected as the main pollution management area.
Groundwater is the main or even the only source of drinking water in the eastern plain of Xinjiang. The pollution status of inorganic components in groundwater and their negative effects on human health are still unclear. The concentrations of common inorganic components in 183 groundwater samples were determined, and the spatial distribution characteristics of pollutants were revealed by GIS technology, positive matrix factorization (PMF) model was used for source apportionment, and the health risks of potential sources were quantified by coupling Monte Carlo simulation (MCS) and PMF based on USEPA health risk assessment model. The groundwater quality in the eastern plain of Xinjiang was mainly affected by SO42- and Cl-, and 30.60% and 17.49% of the groundwater exceeded the limit of national drinking water standard (250 mg·L-1), respectively, the high value points are concentrated in Santanghu Town of Balikun County, the southeast of Gaochang District and the east of Shanshan County. PMF analyzed six potential sources of inorganic components in groundwater, including leaching and evaporation concentration, aquifer lithology, agricultural activity, biogeochemical process, redox environment and geological environment background, the contribution rates were 82.43%, 7.64%, 6.87%, 1.96%, 0.80% and 0.30% respectively. The results of health risk assessment show that Cl- was the main inorganic pollutant harmful to human health, and the non-carcinogenic risk of adults and children could be neglected. The contribution rate of leaching and evaporation concentration to the non-carcinogenic risk of adults and children were more than 95.00%. Considering the safety of drinking water, the high value area of Cl- should be selected as the main pollution management area.
2024, 49(11): 4022-4034.
doi: 10.3799/dqkx.2023.172
Abstract:
The dissolution of stibnite (Sb2S3) is an important source of antimony in the aqueous environment, and the toxicity, mobility and bioavailability of dissolved antimony in water are closely related to its morphology, but the current understanding of the morphological distribution of antimony in the dissolution products of stibnite is not consistent, and the understanding of the particular form of antimony, thioantimonate, is particularly controversial. In this context, it systematically investigated the dissolution process of stibnite and its effect on the formation of thioantimonate under different aqueous conditions, to provide a basis for the accurate evaluation of the environmental effects of stibnite dissolution. The results show that the dissolution of stibnite under acidic-weak alkaline conditions does not lead to the formation of thioantimonate, while under alkaline conditions trithioantimonate and tetrathioantimonate can be formed; the dissolution of stibnite is unlikely to lead to the formation of poly-thioantimonate when the initial total antimony content in the reaction system is comparable to that in natural water. In addition, the coexistence of different types of reduced sulfur or moderate amounts of orpiment and an increase in the ionic strength of the water can promote the formation of thioantimonate, which is inhibited by excess orpiment. The S(-Ⅱ)/Sb molar ratio in water is an important factor in controlling the formation of thioantimonate; the S(-Ⅱ)/Sb molar ratio is a key indicator to be considered when examining the environmental impact of stibnite leaching in natural water environments and the potential for thioantimonate formation during leaching.
The dissolution of stibnite (Sb2S3) is an important source of antimony in the aqueous environment, and the toxicity, mobility and bioavailability of dissolved antimony in water are closely related to its morphology, but the current understanding of the morphological distribution of antimony in the dissolution products of stibnite is not consistent, and the understanding of the particular form of antimony, thioantimonate, is particularly controversial. In this context, it systematically investigated the dissolution process of stibnite and its effect on the formation of thioantimonate under different aqueous conditions, to provide a basis for the accurate evaluation of the environmental effects of stibnite dissolution. The results show that the dissolution of stibnite under acidic-weak alkaline conditions does not lead to the formation of thioantimonate, while under alkaline conditions trithioantimonate and tetrathioantimonate can be formed; the dissolution of stibnite is unlikely to lead to the formation of poly-thioantimonate when the initial total antimony content in the reaction system is comparable to that in natural water. In addition, the coexistence of different types of reduced sulfur or moderate amounts of orpiment and an increase in the ionic strength of the water can promote the formation of thioantimonate, which is inhibited by excess orpiment. The S(-Ⅱ)/Sb molar ratio in water is an important factor in controlling the formation of thioantimonate; the S(-Ⅱ)/Sb molar ratio is a key indicator to be considered when examining the environmental impact of stibnite leaching in natural water environments and the potential for thioantimonate formation during leaching.
2024, 49(11): 4035-4046.
doi: 10.3799/dqkx.2022.431
Abstract:
Many ancient buildings represented by Water Temples are located in the lower reach of the Yuan River in Hunan Province. In ancient times, due to the worship of water god, the water god temples were generally built near, water, mainly for praying for the safety of water transportation and facilitating the navigation. In this paper it interprets the paleohydrological value of ancient buildings, explores the characteristics of droughts and floods in the history of the Yuan River basin, and provides references for the study of regional climate change. Because of the special nature of ancient buildings such as the Water God Temple built by water, so its site marked the ancient shoreline of the Yuan River. In addition, the ancient buildings were built on bases higher than the height of the water level in that year. Data such as the location of the ancient buildings and the elevation of their bases were used to reconstruct the historical river channel changes and drought and flood characteristics of the lower reach of the Yuan River. The ancient buildings represented by the Water God Temple are concentrated on the plain area and the transition zone between hills and plains in the downstream of Yuan River, which corresponds well with the paleohydrological environment such as river channel changes and drought and flood characteristics in the history. The Water God Temple in Zhenlongge proves that the local water is an ancient river channel; the stone cabinet in Wuling District indicates an extremely dry period during the Five Dynasties and Ten Kingdoms period and a flood period during the Kangxi period, the average value of dry and wet climate is calculated for 40 meters from the ancient buildings; above 40 meters is the flooding period, it's the warm climate period, and below 40 meters is the dry period, it's the cold climate period, which provides important values for ancient climate research.
Many ancient buildings represented by Water Temples are located in the lower reach of the Yuan River in Hunan Province. In ancient times, due to the worship of water god, the water god temples were generally built near, water, mainly for praying for the safety of water transportation and facilitating the navigation. In this paper it interprets the paleohydrological value of ancient buildings, explores the characteristics of droughts and floods in the history of the Yuan River basin, and provides references for the study of regional climate change. Because of the special nature of ancient buildings such as the Water God Temple built by water, so its site marked the ancient shoreline of the Yuan River. In addition, the ancient buildings were built on bases higher than the height of the water level in that year. Data such as the location of the ancient buildings and the elevation of their bases were used to reconstruct the historical river channel changes and drought and flood characteristics of the lower reach of the Yuan River. The ancient buildings represented by the Water God Temple are concentrated on the plain area and the transition zone between hills and plains in the downstream of Yuan River, which corresponds well with the paleohydrological environment such as river channel changes and drought and flood characteristics in the history. The Water God Temple in Zhenlongge proves that the local water is an ancient river channel; the stone cabinet in Wuling District indicates an extremely dry period during the Five Dynasties and Ten Kingdoms period and a flood period during the Kangxi period, the average value of dry and wet climate is calculated for 40 meters from the ancient buildings; above 40 meters is the flooding period, it's the warm climate period, and below 40 meters is the dry period, it's the cold climate period, which provides important values for ancient climate research.
2024, 49(11): 4047-4062.
doi: 10.3799/dqkx.2024.083
Abstract:
Global warming has led to environmental changes in the Himalayas, and glacial lake outburst has occurred frequently, having inflicted significant losses upon downstream communities and infrastructure. To understand the spatio-temporal characteristics of Himalayan glacial lake outbursts, it employed geomorphic analysis, time series analysis, and climate perturbation analysis. These methods allowed us to analyze the spatial differentiation and variation characteristics of glaciers, glacial lakes and environments in the Himalayas, and to reveal the evolution patterns of glacial lake outbursts' spatio-temporal distribution in the region. The results show follows: (1) Temperature and precipitation has increased considerably in the Himalayan region between 1980 and 2014, with a more significant increase rate observed on the northern than southern sides. Due to the influence of topography and climate, the northern slope of Himalayas and western Himalayas experienced more severe glacier mass loss. Glacial lakes were predominantly concentrated in the central Himalayas and the southern slope of Himalayas, and the number and area of glacial lakes on the southern slopes have increased more than those on the northern slopes during 1990‒2015, and the new glacial lakes are distributed at a higher elevation than the disappearing ones. (2) Since the 20th century, 249 glacial lake outburst events have occurred in 113 glacial lakes in the Himalayan region and its surrounding areas. The distribution of those glacial lakes is predominantly concentrated in major rivers' steep or extremely steep sections. The number of regional glacial lake outbursts has shown a nonlinear increase trend driven by climate change. The occurrence frequency of glacial lake outburst disasters has a breakpoint of 1966+37/-31 from 1901 to 2020. Furthermore, there is a lag effect of approximately 20 years between the warming rate and the occurrence of glacial lake outburst floods. These research findings can provide a scientific basis for addressing climate change adaptation, disaster risk reduction, and cross-border disaster risk management.
Global warming has led to environmental changes in the Himalayas, and glacial lake outburst has occurred frequently, having inflicted significant losses upon downstream communities and infrastructure. To understand the spatio-temporal characteristics of Himalayan glacial lake outbursts, it employed geomorphic analysis, time series analysis, and climate perturbation analysis. These methods allowed us to analyze the spatial differentiation and variation characteristics of glaciers, glacial lakes and environments in the Himalayas, and to reveal the evolution patterns of glacial lake outbursts' spatio-temporal distribution in the region. The results show follows: (1) Temperature and precipitation has increased considerably in the Himalayan region between 1980 and 2014, with a more significant increase rate observed on the northern than southern sides. Due to the influence of topography and climate, the northern slope of Himalayas and western Himalayas experienced more severe glacier mass loss. Glacial lakes were predominantly concentrated in the central Himalayas and the southern slope of Himalayas, and the number and area of glacial lakes on the southern slopes have increased more than those on the northern slopes during 1990‒2015, and the new glacial lakes are distributed at a higher elevation than the disappearing ones. (2) Since the 20th century, 249 glacial lake outburst events have occurred in 113 glacial lakes in the Himalayan region and its surrounding areas. The distribution of those glacial lakes is predominantly concentrated in major rivers' steep or extremely steep sections. The number of regional glacial lake outbursts has shown a nonlinear increase trend driven by climate change. The occurrence frequency of glacial lake outburst disasters has a breakpoint of 1966+37/-31 from 1901 to 2020. Furthermore, there is a lag effect of approximately 20 years between the warming rate and the occurrence of glacial lake outburst floods. These research findings can provide a scientific basis for addressing climate change adaptation, disaster risk reduction, and cross-border disaster risk management.
2024, 49(11): 4063-4081.
doi: 10.3799/dqkx.2024.075
Abstract:
As one of the critical climatic elements of the Earth system, the permafrost is approaching its climatic tipping point, highlighting the limitations of its two-layered structure consisting of active layer and perennially frozen layer. Therefore, it is necessary to consider the transition zone situated between the active layer and perennially frozen layer, which has specific properties, as a separate layer. The transition zone is the ice-rich upper part of permafrost, which thaws over sub-decadal to centennial time scales, particularly during extremely warm and wet summers, becoming part of the active layer. It comprises an ice-rich transient layer and an icier intermediate layer. The cryostructures, thermophysical properties, and mechanical structures of the transition zone are distinct from both overlying active layer and underlying permafrost, below which is the "authentic" permafrost. Under the combined influence of global climate warming and anthropogenic activities, the degree and extent of permafrost degradation are related to external forcing factors such as climate, environment, basic properties of watershed, and human activities, as well as internal properties like the thickness and position of the transition zone, cryogenic structures, ground ice, and organic matter content, displaying strong spatiotemporal heterogeneity. Research shows that transition zone is widely distributed in silty-clay and parts of frost-susceptible weathered bedrocks with fine-grained pores. It is the main distribution zone of intrasedimental ice and excess ice, with ground ice mainly existing as segregated ice, vein ice, and massive ice. The cryostructures are primarily lenticular, layered, reticular, and ataxitic, and their changes are closely related to phenomena such as thermal subsidence, thermokarst slumping, solifluctions, and active layer detachment. The rich organic matter and humus contained within are often associated with permafrost aggradation and repeated segregation ice formation processes, serving as reliable proxies for reconstructing the climate and environment of permafrost formation. Due to substantial latent heat effects of phase changes in ground ice, the transition zone can slow down or even resist permafrost degradation. However, once it melts, it triggers a tipping point effect, accelerating permafrost degradation, increasing thermokarst phenomena, and leading to the instability of overlying engineering structures. Therefore, it is urgent to carry out research on climate and environmental reconstruction, eco-hydrological effects, mechanical structure evolution, and precise permafrost modeling that includes the transition zone.
As one of the critical climatic elements of the Earth system, the permafrost is approaching its climatic tipping point, highlighting the limitations of its two-layered structure consisting of active layer and perennially frozen layer. Therefore, it is necessary to consider the transition zone situated between the active layer and perennially frozen layer, which has specific properties, as a separate layer. The transition zone is the ice-rich upper part of permafrost, which thaws over sub-decadal to centennial time scales, particularly during extremely warm and wet summers, becoming part of the active layer. It comprises an ice-rich transient layer and an icier intermediate layer. The cryostructures, thermophysical properties, and mechanical structures of the transition zone are distinct from both overlying active layer and underlying permafrost, below which is the "authentic" permafrost. Under the combined influence of global climate warming and anthropogenic activities, the degree and extent of permafrost degradation are related to external forcing factors such as climate, environment, basic properties of watershed, and human activities, as well as internal properties like the thickness and position of the transition zone, cryogenic structures, ground ice, and organic matter content, displaying strong spatiotemporal heterogeneity. Research shows that transition zone is widely distributed in silty-clay and parts of frost-susceptible weathered bedrocks with fine-grained pores. It is the main distribution zone of intrasedimental ice and excess ice, with ground ice mainly existing as segregated ice, vein ice, and massive ice. The cryostructures are primarily lenticular, layered, reticular, and ataxitic, and their changes are closely related to phenomena such as thermal subsidence, thermokarst slumping, solifluctions, and active layer detachment. The rich organic matter and humus contained within are often associated with permafrost aggradation and repeated segregation ice formation processes, serving as reliable proxies for reconstructing the climate and environment of permafrost formation. Due to substantial latent heat effects of phase changes in ground ice, the transition zone can slow down or even resist permafrost degradation. However, once it melts, it triggers a tipping point effect, accelerating permafrost degradation, increasing thermokarst phenomena, and leading to the instability of overlying engineering structures. Therefore, it is urgent to carry out research on climate and environmental reconstruction, eco-hydrological effects, mechanical structure evolution, and precise permafrost modeling that includes the transition zone.
2024, 49(11): 4082-4097.
doi: 10.3799/dqkx.2022.256
Abstract:
The relationship between fault characteristics and hydrocarbon accumulation in southern Ordos basin remains poorly understood though it has been a hot topic for a long time. It was thought that less faults are developed in southern Ordos basin, so stratigraphic and lithologic reservoirs are primary exploration target. However, lots of strike slip faults with big dip, small throws are found as exploration technology improves. Taking the strike-slip fault in Binchang area on the southwest margin of Ordos basin as the research object, using the fine anatomy of fault geometry and kinematics characteristics, combined with the basin structural evolution characteristics, the fault activity period is determined, and the relationship between the structural characteristics of strike-slip fault and hydrocarbon accumulation is discussed. The study shows that the study area can be divided into three structural layers vertically: lower structural layer (Tg‒T9), middle structural layer (T9‒T5), and upper structural layer (above T5). The fault characteristics of the three structural layers show obvious differences, but also have certain similarity and inheritance. The lower structural layer is mainly influenced by Caledonian and Hercynian movements, the middle structural layer is mainly influenced by Indosinian movement, and the upper structural layer is mainly influenced by Yanshanian and Himalayan movements. In general, the development of NEE faults in the study area is obviously inherited and strengthened from bottom to top, while the development of NW faults is gradually weakened. The present fault patterns were mainly formed in the Yanshanian period. In addition, the major fault in the study area is obviously characterized by segmental activity. The complex fault system and the two regional unconformities (T9 and T5) control the Paleozoic and Mesozoic hydrocarbon accumulation systems in the study area. Plenty of faults and fractures provided the seepage channels and storage space for the Mesozoic tight reservoirs with low permeability, resulting in the formation of lots of fault-fracture clastic reservoirs. The fracture development level and local structural high points control the high-yield and enrichment of fault-fracture clastic reservoirs.
The relationship between fault characteristics and hydrocarbon accumulation in southern Ordos basin remains poorly understood though it has been a hot topic for a long time. It was thought that less faults are developed in southern Ordos basin, so stratigraphic and lithologic reservoirs are primary exploration target. However, lots of strike slip faults with big dip, small throws are found as exploration technology improves. Taking the strike-slip fault in Binchang area on the southwest margin of Ordos basin as the research object, using the fine anatomy of fault geometry and kinematics characteristics, combined with the basin structural evolution characteristics, the fault activity period is determined, and the relationship between the structural characteristics of strike-slip fault and hydrocarbon accumulation is discussed. The study shows that the study area can be divided into three structural layers vertically: lower structural layer (Tg‒T9), middle structural layer (T9‒T5), and upper structural layer (above T5). The fault characteristics of the three structural layers show obvious differences, but also have certain similarity and inheritance. The lower structural layer is mainly influenced by Caledonian and Hercynian movements, the middle structural layer is mainly influenced by Indosinian movement, and the upper structural layer is mainly influenced by Yanshanian and Himalayan movements. In general, the development of NEE faults in the study area is obviously inherited and strengthened from bottom to top, while the development of NW faults is gradually weakened. The present fault patterns were mainly formed in the Yanshanian period. In addition, the major fault in the study area is obviously characterized by segmental activity. The complex fault system and the two regional unconformities (T9 and T5) control the Paleozoic and Mesozoic hydrocarbon accumulation systems in the study area. Plenty of faults and fractures provided the seepage channels and storage space for the Mesozoic tight reservoirs with low permeability, resulting in the formation of lots of fault-fracture clastic reservoirs. The fracture development level and local structural high points control the high-yield and enrichment of fault-fracture clastic reservoirs.
2024, 49(11): 4098-4111.
doi: 10.3799/dqkx.2022.180
Abstract:
When deep water drilling meets combustible ice formation, the invasion of drilling fluid accompanied by mass and heat transfer will have an important impact on the mechanical stability of the formation near the wellbore, changing the physical properties of the formation, and affecting the quality and accuracy of subsequent well logging. To address the problem, this paper takes the Gulf of Mexico Gas Hydrate Joint Industry Project (JIP) as the research object. Firstly, the artificial formation skeleton with physical parameters close to the actual is prepared by pressing cementation method. Then, the physical property response law of the formation near the wellbore during the invasion of drilling fluid under the conditions of in-situ reservoir geology and drilling technology is experimentally studied, and the effects of mass transfer and heat transfer behavior on formation temperature, pressure and resistivity are analyzed. The influence mechanism of temperature difference and pressure difference is obtained, and the functional relationship between invasion depth and time is established. The results show that the porosity and resistivity of the artificial reservoir skeleton optimized by orthogonal test are very close to those of the in-situ formation, with the difference of 1.29% and 4.0% respectively. The influence range of pressure is much faster than that of temperature and resistivity, and their influence range has a strong mathematical relationship with time. The decomposition of hydrate occurs successively with the increase of invasion depth, which is manifested in the change of resistivity. The free gas and water produced by decomposition migrate to the deeper, which is easy to reform hydrate in the area between the temperature and pressure variation range, showing a highly saturated hydrate zone. In the range of formation fracture pressure, the positive differential pressure plays a positive role in maintaining the stability of hydrate phase, which is conducive to the stability of near wellbore formation, while the effect of temperature difference is just the opposite. In the process of field drilling, the impact on the formation can be reduced by increasing the density and salinity of drilling fluid, reducing the filtration loss and adding inhibitors. The 12 hours resistivity variation depth is about 0.65 m. Therefore, in order to obtain the resistivity data of undisturbed hydrate reservoir during resistivity logging, the time interval between drilling and logging should be reduced. Logging while drilling or logging methods with appropriate detection depth, such as non-shallow lateral logging, can be used.
When deep water drilling meets combustible ice formation, the invasion of drilling fluid accompanied by mass and heat transfer will have an important impact on the mechanical stability of the formation near the wellbore, changing the physical properties of the formation, and affecting the quality and accuracy of subsequent well logging. To address the problem, this paper takes the Gulf of Mexico Gas Hydrate Joint Industry Project (JIP) as the research object. Firstly, the artificial formation skeleton with physical parameters close to the actual is prepared by pressing cementation method. Then, the physical property response law of the formation near the wellbore during the invasion of drilling fluid under the conditions of in-situ reservoir geology and drilling technology is experimentally studied, and the effects of mass transfer and heat transfer behavior on formation temperature, pressure and resistivity are analyzed. The influence mechanism of temperature difference and pressure difference is obtained, and the functional relationship between invasion depth and time is established. The results show that the porosity and resistivity of the artificial reservoir skeleton optimized by orthogonal test are very close to those of the in-situ formation, with the difference of 1.29% and 4.0% respectively. The influence range of pressure is much faster than that of temperature and resistivity, and their influence range has a strong mathematical relationship with time. The decomposition of hydrate occurs successively with the increase of invasion depth, which is manifested in the change of resistivity. The free gas and water produced by decomposition migrate to the deeper, which is easy to reform hydrate in the area between the temperature and pressure variation range, showing a highly saturated hydrate zone. In the range of formation fracture pressure, the positive differential pressure plays a positive role in maintaining the stability of hydrate phase, which is conducive to the stability of near wellbore formation, while the effect of temperature difference is just the opposite. In the process of field drilling, the impact on the formation can be reduced by increasing the density and salinity of drilling fluid, reducing the filtration loss and adding inhibitors. The 12 hours resistivity variation depth is about 0.65 m. Therefore, in order to obtain the resistivity data of undisturbed hydrate reservoir during resistivity logging, the time interval between drilling and logging should be reduced. Logging while drilling or logging methods with appropriate detection depth, such as non-shallow lateral logging, can be used.
2024, 49(11): 4112-4129.
doi: 10.3799/dqkx.2023.169
Abstract:
The dynamic source of the Paleozoic multistage tectonic pattern changes in Tarim basin, especially the reason for the sharp change of the basin tectonic pattern in the Middle and Late Early Paleozoic, has always been the focus of controversy among many scholars. Based on the analysis of heavy mineral assemblages, in this paper it conducts a detailed U-Pb chronological study of detrital zircons from the Furongian to the Cisuralian sandstone samples in Keping area, northwest margin of Tarim basin, in order to determine the provenance system of Keping area, and describe the sedimentary tectonic evolution process of this area. The results show that the detrital zircon samples recorded five tectonic thermal events at 500-420 Ma, 870-710 Ma, 1 100-880 Ma, 2 000-1 710 Ma, and 2 570-2 400 Ma, with the previous three periods being the main age. Compared with the potential provenance areas, the palaeouplift in Tarim basin has always been an important provenance area in Keping area during the Furongian; In addition to the palaeouplift within the basin, there may also be two source areas during the Silurian to the Devonian. The northern source area is the northern margin of the Tarim craton, and the southern source area may be the West Kunlun orogenic belt. The main source of study area is the palaeouplift within the basin during the Carboniferous to the earliest Permian, which originated from the erosion of previous strata. Comprehensive research suggests that the Middle Tianshan terrane may have been connected to the Tarim craton before the Early and Middle Devonian. After this period, the Middle Tianshan terrane gradually separated from the Tarim craton, and the South Tianshan Ocean gradually formed. Correspondingly, due to the formation, subduction, closure of the ocean basin on the north side of the Tarim craton, the structural attributes of the northern margin of the basin have undergone multi-stage changes.
The dynamic source of the Paleozoic multistage tectonic pattern changes in Tarim basin, especially the reason for the sharp change of the basin tectonic pattern in the Middle and Late Early Paleozoic, has always been the focus of controversy among many scholars. Based on the analysis of heavy mineral assemblages, in this paper it conducts a detailed U-Pb chronological study of detrital zircons from the Furongian to the Cisuralian sandstone samples in Keping area, northwest margin of Tarim basin, in order to determine the provenance system of Keping area, and describe the sedimentary tectonic evolution process of this area. The results show that the detrital zircon samples recorded five tectonic thermal events at 500-420 Ma, 870-710 Ma, 1 100-880 Ma, 2 000-1 710 Ma, and 2 570-2 400 Ma, with the previous three periods being the main age. Compared with the potential provenance areas, the palaeouplift in Tarim basin has always been an important provenance area in Keping area during the Furongian; In addition to the palaeouplift within the basin, there may also be two source areas during the Silurian to the Devonian. The northern source area is the northern margin of the Tarim craton, and the southern source area may be the West Kunlun orogenic belt. The main source of study area is the palaeouplift within the basin during the Carboniferous to the earliest Permian, which originated from the erosion of previous strata. Comprehensive research suggests that the Middle Tianshan terrane may have been connected to the Tarim craton before the Early and Middle Devonian. After this period, the Middle Tianshan terrane gradually separated from the Tarim craton, and the South Tianshan Ocean gradually formed. Correspondingly, due to the formation, subduction, closure of the ocean basin on the north side of the Tarim craton, the structural attributes of the northern margin of the basin have undergone multi-stage changes.
2024, 49(11): 4130-4155.
doi: 10.3799/dqkx.2023.183
Abstract:
The chemical kinetics model of the reflectance of vitrinite and bitumen is the most used research method to calibrate the thermal history of basin and predict the thermal evolution of source rocks. In recent years, important research progress has been made, but it has not attracted much attention from domestic researchers. Based on reviewing the research process of the chemical kinetic model of organic matter, in this paper it reports the new progress of relevant research. The classical Vitrimat model and Easy%Ro model are based on three principles: (1) the vitrinite reflectance is related to H/C and O/C. (2) The thermal degradation product of vitrinite was the sum of residual vitrinite and four kinds of products (H2O, CO2, CHn, CH4). (3) Thermal degradation reaction follows Arrhenius equation. Easy%Ro model has design defects: (1) the frequency factor (1×1013) is too low; (2) lack of high maturity (Ro > 2.0%) samples when optimizing activation energy distribution. The shortcomings in practical application include: (1) when the measured Ro < 0.9%, the calculated value of Easy%Ro is too high; (2) when the measured Ro > 2.0%, the calculated value of the Easy%Ro model is too low. New models Basin%Ro, Easy%RoDL, Easy%RoV and Easy%RoB (bitumen) are designed to overcome the obvious shortcomings of the Easy%Ro kinetics model, but the data basis, calibration principles and potential applicability of each model are different. The "dog-leg" curve characteristic of BasinRo% model at medium-low maturity stage may not be applicable to vitrinite reflectance-depth profile; The Easy%RoDL model has strong applicability to geological conditions; Easy%RoV is more suitable for laboratory heating rate conditions. At the geological heating rate, the new chemical kinetics models developed for Ro have all improved the calculated values when Ro > 2.0 %. Easy%RoB is a kinetics model designed for BRo based on the function relation of BRo-VRo (equivalent Vitinite reflectance) and Vitrimat 2018 (Type-Ⅱ) model, which has high applicability to geological conditions. Calibration chemical kinetics module and Kinetics hydrocarbon generation kinetics module in PetroMod basin simulation platform were used to carry out three studies: (1) calibration and prediction of ultra-deep source rock maturity, (2) thermal history and basin dynamics derived from vitrinite reflectance of medium to low maturity source rocks, (3) establishment of hydrocarbon generation model combined with hydrocarbon generation kinetics parameters. In the future, attention should be paid to the study of the adaptability of the new chemical kinetics models under laboratory/geological conditions. Improving the accuracy of reflectance measurement, correctly identifying the degree of reflectance inhibition, and being coupled with low temperature thermochronology parameter inversion are of great significance for improving the accuracy of basin thermal history research using chemical kinetics models.
The chemical kinetics model of the reflectance of vitrinite and bitumen is the most used research method to calibrate the thermal history of basin and predict the thermal evolution of source rocks. In recent years, important research progress has been made, but it has not attracted much attention from domestic researchers. Based on reviewing the research process of the chemical kinetic model of organic matter, in this paper it reports the new progress of relevant research. The classical Vitrimat model and Easy%Ro model are based on three principles: (1) the vitrinite reflectance is related to H/C and O/C. (2) The thermal degradation product of vitrinite was the sum of residual vitrinite and four kinds of products (H2O, CO2, CHn, CH4). (3) Thermal degradation reaction follows Arrhenius equation. Easy%Ro model has design defects: (1) the frequency factor (1×1013) is too low; (2) lack of high maturity (Ro > 2.0%) samples when optimizing activation energy distribution. The shortcomings in practical application include: (1) when the measured Ro < 0.9%, the calculated value of Easy%Ro is too high; (2) when the measured Ro > 2.0%, the calculated value of the Easy%Ro model is too low. New models Basin%Ro, Easy%RoDL, Easy%RoV and Easy%RoB (bitumen) are designed to overcome the obvious shortcomings of the Easy%Ro kinetics model, but the data basis, calibration principles and potential applicability of each model are different. The "dog-leg" curve characteristic of BasinRo% model at medium-low maturity stage may not be applicable to vitrinite reflectance-depth profile; The Easy%RoDL model has strong applicability to geological conditions; Easy%RoV is more suitable for laboratory heating rate conditions. At the geological heating rate, the new chemical kinetics models developed for Ro have all improved the calculated values when Ro > 2.0 %. Easy%RoB is a kinetics model designed for BRo based on the function relation of BRo-VRo (equivalent Vitinite reflectance) and Vitrimat 2018 (Type-Ⅱ) model, which has high applicability to geological conditions. Calibration chemical kinetics module and Kinetics hydrocarbon generation kinetics module in PetroMod basin simulation platform were used to carry out three studies: (1) calibration and prediction of ultra-deep source rock maturity, (2) thermal history and basin dynamics derived from vitrinite reflectance of medium to low maturity source rocks, (3) establishment of hydrocarbon generation model combined with hydrocarbon generation kinetics parameters. In the future, attention should be paid to the study of the adaptability of the new chemical kinetics models under laboratory/geological conditions. Improving the accuracy of reflectance measurement, correctly identifying the degree of reflectance inhibition, and being coupled with low temperature thermochronology parameter inversion are of great significance for improving the accuracy of basin thermal history research using chemical kinetics models.
2024, 49(11): 4156-4168.
doi: 10.3799/dqkx.2023.220
Abstract:
Dissolved organic matter (DOM) is composed of complex organic mixtures in diverse environments and plays critical roles in governing the environmental fate and transport of pollutants and nutritious elements and the global carbon cycle. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is the most advanced mass technique for the molecular composition of organic matter, with great importance in elucidating the ecological and environmental significance of DOM. This bibliometrics study based on Web of Science database was performed to visually analyze the current status, hot spots, trends and typical applications of FT-ICR MS in environmental earth science research. The results show that Mainland China has the largest number of publications in this field, followed by the United States. Environmental science is the most published among all disciplines with the most prolific journal, Environmental Science & Technology. The most productive domestic and foreign authors are Prof. Shi Quan, Dr. He Cen and Prof. Thorsten Dittmar in this field, respectively. The relevant research is mainly focused on air, groundwater, biological community, drinking water disinfection and water treatment. In addition, typical applications are reviewed to facilitate our understanding in the high-throughput and non-targeted qualitative analysis of DOM. For the first time, this bibliometrics study reports the current research status and hot spots of FT-ICR MS in the molecular characterization of DOM from diverse environments, highlighting its great potential in environmental earth science research.
Dissolved organic matter (DOM) is composed of complex organic mixtures in diverse environments and plays critical roles in governing the environmental fate and transport of pollutants and nutritious elements and the global carbon cycle. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is the most advanced mass technique for the molecular composition of organic matter, with great importance in elucidating the ecological and environmental significance of DOM. This bibliometrics study based on Web of Science database was performed to visually analyze the current status, hot spots, trends and typical applications of FT-ICR MS in environmental earth science research. The results show that Mainland China has the largest number of publications in this field, followed by the United States. Environmental science is the most published among all disciplines with the most prolific journal, Environmental Science & Technology. The most productive domestic and foreign authors are Prof. Shi Quan, Dr. He Cen and Prof. Thorsten Dittmar in this field, respectively. The relevant research is mainly focused on air, groundwater, biological community, drinking water disinfection and water treatment. In addition, typical applications are reviewed to facilitate our understanding in the high-throughput and non-targeted qualitative analysis of DOM. For the first time, this bibliometrics study reports the current research status and hot spots of FT-ICR MS in the molecular characterization of DOM from diverse environments, highlighting its great potential in environmental earth science research.
2024, 49(11): 4169-4183.
doi: 10.3799/dqkx.2024.043
Abstract:
The soil layers in permafrost regions store a large amount of organic carbon. However, the understanding of the influence of dissolved organic matter (DOM) in permafrost and seasonally frozen ground on the DOM characteristics of riverine output is still unclear due to limited existing studies on the characteristics of soil organic matter in permafrost and seasonally frozen ground and their differences in alpine catchments. To understand the distributions, and controlling mechanisms of dissolved organic matter in the soil of alpine catchments on aquatic DOM, this study collected soil samples of permafrost and seasonally frozen ground in the Hulugou catchment in the northeastern part of the Tibetan plateau and analyzed the soil organic carbon (SOC), dissolved organic carbon (DOC) content, spectral characteristics of DOM, and its biodegradable dissolved organic carbon (BDOC). Then, DOM characteristics in soils were compared with those from different water bodies at different seasons. The study reveals significant differences between permafrost and seasonally frozen soils in terms of dissolved organic carbon (DOC) biodegradability and microbial activity. Permafrost soils have higher soil organic carbon (SOC) but lower DOC, and their dissolved organic matter (DOM) is less humified and aromatic compared to seasonally frozen soils, where biodegradable DOC (BDOC) proportions are higher. The findings indicate that soil hydrological traits in cold mountain areas significantly influence soil organic matter, highlighting soil moisture as a critical factor. In permafrost areas, shallow soil DOM crucially affects river water DOC concentrations and composition. In contrast, seasonal permafrost zone soils have less direct influence on changes in stream DOC concentration and composition, with hydrological conditions shaping DOM's output features in water bodies. This research is crucial for understanding carbon cycling under permafrost degradation in cold mountain regions, condensed into a comprehensive summary within the specified word limit.
The soil layers in permafrost regions store a large amount of organic carbon. However, the understanding of the influence of dissolved organic matter (DOM) in permafrost and seasonally frozen ground on the DOM characteristics of riverine output is still unclear due to limited existing studies on the characteristics of soil organic matter in permafrost and seasonally frozen ground and their differences in alpine catchments. To understand the distributions, and controlling mechanisms of dissolved organic matter in the soil of alpine catchments on aquatic DOM, this study collected soil samples of permafrost and seasonally frozen ground in the Hulugou catchment in the northeastern part of the Tibetan plateau and analyzed the soil organic carbon (SOC), dissolved organic carbon (DOC) content, spectral characteristics of DOM, and its biodegradable dissolved organic carbon (BDOC). Then, DOM characteristics in soils were compared with those from different water bodies at different seasons. The study reveals significant differences between permafrost and seasonally frozen soils in terms of dissolved organic carbon (DOC) biodegradability and microbial activity. Permafrost soils have higher soil organic carbon (SOC) but lower DOC, and their dissolved organic matter (DOM) is less humified and aromatic compared to seasonally frozen soils, where biodegradable DOC (BDOC) proportions are higher. The findings indicate that soil hydrological traits in cold mountain areas significantly influence soil organic matter, highlighting soil moisture as a critical factor. In permafrost areas, shallow soil DOM crucially affects river water DOC concentrations and composition. In contrast, seasonal permafrost zone soils have less direct influence on changes in stream DOC concentration and composition, with hydrological conditions shaping DOM's output features in water bodies. This research is crucial for understanding carbon cycling under permafrost degradation in cold mountain regions, condensed into a comprehensive summary within the specified word limit.
2024, 49(11): 4184-4203.
doi: 10.3799/dqkx.2024.067
Abstract:
In this review it focuses on the detection history and research progress of extraterrestrial organic matter, exploring the species, structures, chemical compositions, and isotopic compositions of organic matter in the interstellar medium, extraterrestrial bodies, and extraterrestrial samples. The goal is to comprehend the origins of extraterrestrial organic matter, to address the related scientific issues and to explore its implications for astrobiology. The widespread distribution of organic molecules in the interstellar medium suggests that organic matter is not exclusive to Earth or the Solar System, but rather is present throughout the universe. Carbonaceous chondrites contain a variety of organic substances, including alcohols, amino acids, and carboxylic acids. The progress in space exploration has led to remarkable findings, including the detection of methane fluctuations in the Martian atmosphere, widespread coverage of liquid hydrocarbons on Titan's surface, the glycine in the comets, and the confirmation of extraterrestrial amino acids in asteroidal samples. These recent discoveries indicate that organic matter may be widely distributed throughout the Solar System and provide critical insights into the search for extraterrestrial life and the origins of life.
In this review it focuses on the detection history and research progress of extraterrestrial organic matter, exploring the species, structures, chemical compositions, and isotopic compositions of organic matter in the interstellar medium, extraterrestrial bodies, and extraterrestrial samples. The goal is to comprehend the origins of extraterrestrial organic matter, to address the related scientific issues and to explore its implications for astrobiology. The widespread distribution of organic molecules in the interstellar medium suggests that organic matter is not exclusive to Earth or the Solar System, but rather is present throughout the universe. Carbonaceous chondrites contain a variety of organic substances, including alcohols, amino acids, and carboxylic acids. The progress in space exploration has led to remarkable findings, including the detection of methane fluctuations in the Martian atmosphere, widespread coverage of liquid hydrocarbons on Titan's surface, the glycine in the comets, and the confirmation of extraterrestrial amino acids in asteroidal samples. These recent discoveries indicate that organic matter may be widely distributed throughout the Solar System and provide critical insights into the search for extraterrestrial life and the origins of life.
2024, 49(11): 4204-4215.
doi: 10.3799/dqkx.2022.147
Abstract:
When a tunnel collapse occurs, decision makers often do not have enough reaction time to take appropriate reinforcement measures. Advance prediction of tunnel collapse failure probability has become a key issue in tunnel engineering construction. As for assessing the tunneling collapse failure probability and providing basic risk-controlling strategies, in this study it proposes a novel multi-source information fusion approach that combines the cloud model (CM), the multi-output gaussian process regression (MOGPR), and the improved D-S evidence theory. The fusion of multiple monitoring data (vault displacement, horizontal convergence displacement) reduces data uncertainty and improves the accuracy and robustness of assessment results. In addition, the surrounding rock deformation predicted by artificial intelligence is used as a source of information to obtain an advanced collapse failure probability assessment. As a result, decision makers have a longer response time before the collapse occurs. Applying the method to the Jinzhupa tunnel provides decision makers with more response time. In the end, only a small amount of deformation cracks were generated in the surrounding rock support, avoiding the tunnel collapse.
When a tunnel collapse occurs, decision makers often do not have enough reaction time to take appropriate reinforcement measures. Advance prediction of tunnel collapse failure probability has become a key issue in tunnel engineering construction. As for assessing the tunneling collapse failure probability and providing basic risk-controlling strategies, in this study it proposes a novel multi-source information fusion approach that combines the cloud model (CM), the multi-output gaussian process regression (MOGPR), and the improved D-S evidence theory. The fusion of multiple monitoring data (vault displacement, horizontal convergence displacement) reduces data uncertainty and improves the accuracy and robustness of assessment results. In addition, the surrounding rock deformation predicted by artificial intelligence is used as a source of information to obtain an advanced collapse failure probability assessment. As a result, decision makers have a longer response time before the collapse occurs. Applying the method to the Jinzhupa tunnel provides decision makers with more response time. In the end, only a small amount of deformation cracks were generated in the surrounding rock support, avoiding the tunnel collapse.
2024, 49(11): 4216-4224.
doi: 10.3799/dqkx.2022.499
Abstract:
Conventional mechanical analysis methods for slope stability have limited computational efficiency and need professional software. Machine learning, as an efficient analysis method, can be applied to slope stability evaluation. Abundant broken line slope samples are randomly generated and the corresponding factors of safety are solved by the limit equilibrium method (LEM) in this paper, so as to build a slope factor of safety database, and the LEM surrogate model is established by integrating neural network models. Two ensemble algorithms, Bagging and AdaBoost.R2, are used to establish a neural network ensemble model to predict factor of safety, which is verified by practical slope engineering cases, contrasting with single neural network model. The performances are evaluated by ROC curve analysis method, and reasonable threshold of factor of safety is determined. Results show that two ensemble models are significantly better than the single neural network model. While the AUC value of the single neural network model is 0.826, the AdaBoost. R2 model is 0.893, and the Bagging model can recognize slope stability situation better with value of 0.929. The proposed method can evaluate broken line slope stability quickly and accurately, providing a tool for rapid stability evaluation of a large number of regional slopes.
Conventional mechanical analysis methods for slope stability have limited computational efficiency and need professional software. Machine learning, as an efficient analysis method, can be applied to slope stability evaluation. Abundant broken line slope samples are randomly generated and the corresponding factors of safety are solved by the limit equilibrium method (LEM) in this paper, so as to build a slope factor of safety database, and the LEM surrogate model is established by integrating neural network models. Two ensemble algorithms, Bagging and AdaBoost.R2, are used to establish a neural network ensemble model to predict factor of safety, which is verified by practical slope engineering cases, contrasting with single neural network model. The performances are evaluated by ROC curve analysis method, and reasonable threshold of factor of safety is determined. Results show that two ensemble models are significantly better than the single neural network model. While the AUC value of the single neural network model is 0.826, the AdaBoost. R2 model is 0.893, and the Bagging model can recognize slope stability situation better with value of 0.929. The proposed method can evaluate broken line slope stability quickly and accurately, providing a tool for rapid stability evaluation of a large number of regional slopes.
2024, 49(11): 4225-4237.
doi: 10.3799/dqkx.2023.055
Abstract:
The spatial variabilities of stratigraphy and S-wave velocity (Vs) structures have significant influence on the results of seismic site response analyses. Based on the borehole data of the seabed of Bohai Bay, the embedded Markov chain model, which has a wider simulation range for random stratigraphy and smoother simulation effect for stratigraphic boundary than the coupled Markov chain, is used to simulate the variabilities of random stratigraphy with depth less than the borehole bottoms, and the simulation results have higher precision. The point estimation method is used to give the change of the means and standard deviations of Vs with h of the seabed when describing the variation trend of Vs with h by power function and linear function. Based on the measured Vs-profiles at the boreholes, the spatial variabilities of random Vs-structures are simulated by using the non-stationary conditional random field method. It is found that considering the spatial variabilities of the random stratigraphy and ignoring the nonlinear variation of Vs along h can significantly increase the standard deviations of the simulated random Vs- structures. The correlations and transfer probabilities between the unknown stratigraphy below the seabed borehole bottoms and the known stratigraphy at the same depth of near-shore land are established using the membership function and fuzzy Markov chain model, the possible spatial variabilities of random seabed stratigraphy and Vs-structures below the borehole bottoms are obtained. It provides reasonable random stratigraphy and Vs-structures for seismic response analysis of offshore engineering site.
The spatial variabilities of stratigraphy and S-wave velocity (Vs) structures have significant influence on the results of seismic site response analyses. Based on the borehole data of the seabed of Bohai Bay, the embedded Markov chain model, which has a wider simulation range for random stratigraphy and smoother simulation effect for stratigraphic boundary than the coupled Markov chain, is used to simulate the variabilities of random stratigraphy with depth less than the borehole bottoms, and the simulation results have higher precision. The point estimation method is used to give the change of the means and standard deviations of Vs with h of the seabed when describing the variation trend of Vs with h by power function and linear function. Based on the measured Vs-profiles at the boreholes, the spatial variabilities of random Vs-structures are simulated by using the non-stationary conditional random field method. It is found that considering the spatial variabilities of the random stratigraphy and ignoring the nonlinear variation of Vs along h can significantly increase the standard deviations of the simulated random Vs- structures. The correlations and transfer probabilities between the unknown stratigraphy below the seabed borehole bottoms and the known stratigraphy at the same depth of near-shore land are established using the membership function and fuzzy Markov chain model, the possible spatial variabilities of random seabed stratigraphy and Vs-structures below the borehole bottoms are obtained. It provides reasonable random stratigraphy and Vs-structures for seismic response analysis of offshore engineering site.
2024, 49(11): 4238-4248.
doi: 10.3799/dqkx.2024.063
Abstract:
Polygonal faults are widely developed in continental sedimentary basins. However, their growth processes and mechanism are still unclear. Based on high-resolution 3D seismic data in the Great South Basin of New Zealand, in this study it focuses on the characteristics, growth processes and growth pattern of polygonal faults. According to the geometric characteristics of polygonal faults, they are divided into two tiers (Tier1 and Tier2). The throw profiles of polygonal faults are "C" type, double "C" type and "B" type. According to the geometric and growth characteristics, it proposes the growth pattern of cross-layer polygonal faults. Polygonal faults initially nucleated at the center of the lower layer (Tier1) and grew in all directions. Following a period of quiescence, polygonal faults nucleated in the center of the new (upper) layer (Tier2). Polygonal faults in the overlying layer were gradually connected with those in the underlying layer, forming the relay zones and a cross-layer "large fault". This study reveals the growth processes of polygonal faults such as nucleation, growth and cessation. The related research results can contribute to the hydrocarbon exploration and development, disaster prevention and mitigation.
Polygonal faults are widely developed in continental sedimentary basins. However, their growth processes and mechanism are still unclear. Based on high-resolution 3D seismic data in the Great South Basin of New Zealand, in this study it focuses on the characteristics, growth processes and growth pattern of polygonal faults. According to the geometric characteristics of polygonal faults, they are divided into two tiers (Tier1 and Tier2). The throw profiles of polygonal faults are "C" type, double "C" type and "B" type. According to the geometric and growth characteristics, it proposes the growth pattern of cross-layer polygonal faults. Polygonal faults initially nucleated at the center of the lower layer (Tier1) and grew in all directions. Following a period of quiescence, polygonal faults nucleated in the center of the new (upper) layer (Tier2). Polygonal faults in the overlying layer were gradually connected with those in the underlying layer, forming the relay zones and a cross-layer "large fault". This study reveals the growth processes of polygonal faults such as nucleation, growth and cessation. The related research results can contribute to the hydrocarbon exploration and development, disaster prevention and mitigation.
2024, 49(11): 4249-4264.
doi: 10.3799/dqkx.2024.058
Abstract:
The red bed is one of the representative sedimentary formations in the lithosphere. Its wide distribution, great thickness, typical deposition, and intact landforms are rare. At the same time, it is also an important carrier of Chinese civilization and cultural inheritance. For a long time, the red bed has been one of the hot topics in the fields of geology, engineering, ecology, and materials. However, since the concept of red bed was proposed by British engineers in 1835 and Mr. Li Siguang in 1925, there has not been a unified understanding of red bed, and there is a lack of systematic summarization of red bed identification and its scientific significance, which restricts a comprehensive understanding of the red bed and makes it difficult to meet the needs of red bed scientific development. Therefore, in this paper it systematically reviews the main process of red bed identification in four stages, including the vague distinction of lithological characteristics, clear identification of geomorphic colors, qualitative identification of stratigraphic patterns, and quantitative determination of geological genes, summarizing the scientific significance of red bed identification at different stages. It discusses the trends and main directions of red bed identification, such as geological evolution correlation, object category expansion, and material property models. Finally, based on this foundation, the value and prospects of red bed identification are proposed.
The red bed is one of the representative sedimentary formations in the lithosphere. Its wide distribution, great thickness, typical deposition, and intact landforms are rare. At the same time, it is also an important carrier of Chinese civilization and cultural inheritance. For a long time, the red bed has been one of the hot topics in the fields of geology, engineering, ecology, and materials. However, since the concept of red bed was proposed by British engineers in 1835 and Mr. Li Siguang in 1925, there has not been a unified understanding of red bed, and there is a lack of systematic summarization of red bed identification and its scientific significance, which restricts a comprehensive understanding of the red bed and makes it difficult to meet the needs of red bed scientific development. Therefore, in this paper it systematically reviews the main process of red bed identification in four stages, including the vague distinction of lithological characteristics, clear identification of geomorphic colors, qualitative identification of stratigraphic patterns, and quantitative determination of geological genes, summarizing the scientific significance of red bed identification at different stages. It discusses the trends and main directions of red bed identification, such as geological evolution correlation, object category expansion, and material property models. Finally, based on this foundation, the value and prospects of red bed identification are proposed.
