2020 Vol. 45, No. 3
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2020, 45(3): 711-727.
doi: 10.3799/dqkx.2019.068
Abstract:
The southern margin of the Paleo-Asian Ocean spanned Xinjiang, Gansu, Inner Mongolia, Heilongjiang and other places of China. This paper summarizes the history of Paleozoic tectonic evolution of Paleo-Asian Ocean and addresses the debates on the evolution. Based on the analysis of outcrops of the Upper Paleozoic and researches on paleontology (including brachiopods, radiolarians and plants) through the Paleo-Asian Ocean Domain in China, two conclusions are made. Firstly, during the Early Palaeozoic, the main basin of the Paleo-Asian Ocean might be located in the Tianshan area within western China and in the Airgin Sum-Hegenshan-Linxi-Heihe area within middle and eastern China. During the Late Paleozoic, the main basin of the Paleo-Asian Ocean might be located in the South Tianshan area within western China and in the Solonker-Ondor Sum-Xar Moron-Yanji area within middle and eastern China. Secondly, the west part of the Paleo-Asian Ocean might have been closed in the Early Carboniferous to the Middle Permian while the east part has been closed in the Late Permian. However, the north part of the ocean in Beishan area and the southwest part of the ocean in the South Tianshan persisted to the end-Permian at least. Additionally, this study proposes the potential application of palaeontology (i.e., radiolarians, fusulinids, corals) and of palaeoecology of benthic faunas in the evolution of Paleo-Asian Ocean.
The southern margin of the Paleo-Asian Ocean spanned Xinjiang, Gansu, Inner Mongolia, Heilongjiang and other places of China. This paper summarizes the history of Paleozoic tectonic evolution of Paleo-Asian Ocean and addresses the debates on the evolution. Based on the analysis of outcrops of the Upper Paleozoic and researches on paleontology (including brachiopods, radiolarians and plants) through the Paleo-Asian Ocean Domain in China, two conclusions are made. Firstly, during the Early Palaeozoic, the main basin of the Paleo-Asian Ocean might be located in the Tianshan area within western China and in the Airgin Sum-Hegenshan-Linxi-Heihe area within middle and eastern China. During the Late Paleozoic, the main basin of the Paleo-Asian Ocean might be located in the South Tianshan area within western China and in the Solonker-Ondor Sum-Xar Moron-Yanji area within middle and eastern China. Secondly, the west part of the Paleo-Asian Ocean might have been closed in the Early Carboniferous to the Middle Permian while the east part has been closed in the Late Permian. However, the north part of the ocean in Beishan area and the southwest part of the ocean in the South Tianshan persisted to the end-Permian at least. Additionally, this study proposes the potential application of palaeontology (i.e., radiolarians, fusulinids, corals) and of palaeoecology of benthic faunas in the evolution of Paleo-Asian Ocean.
2020, 45(3): 728-738.
doi: 10.3799/dqkx.2019.017
Abstract:
In order to define the base of the Drumian Stage and the base of the Paibian Stage of Cambrian in North China, carbon isotope trend is studied on the Shatan section, northern Henan. Data of carbon isotope suggest that three positive excursions and two negative excursions have been examined within the measured stratigraphical interval. Positive carbon isotope excursions occur separately in the lower part and the middle part of the Changhia Formation and in the upper part of the Chaumitien Formation, maximum δ13C values of these positive excursions reach to 2.0‰, 1.0‰ and 3.0‰ respectively. Negative δ13C excursions occur in the basal and the lower-middle part of the Changhia Formation with the minimum values of -3.4‰ and -1.0‰ respectively. Especially, the remarkable positive excursion examined in the upper part of the Chaumitien Formation commences on the base of the trilobite Chuangia zone, which corresponds to the base of the Paibian Stage in South China and is equivalent to the SPICE excursion detected in the Paibian Stage in USA, Australia, and Kazakhstan. The negative excursion examined in the basal part of the Changhia Formation is equivalent to the DICE excursion. Both the two carbon isotope excursions are not only used as tools for the regional stratigraphical classification and correlation, but also used as key indicators in defining the Drumian Stage and the Paibian Stage in North China. In addition, carbon isotope excursions are interpreted to be associated with global scale sea-level fluctuations, paleoecological environmental changes. Seawater transgression together with enlargement of paleoecological environment played an important role in positive carbon isotope excursions during the Late Miaolingian to the Early Furongian.
In order to define the base of the Drumian Stage and the base of the Paibian Stage of Cambrian in North China, carbon isotope trend is studied on the Shatan section, northern Henan. Data of carbon isotope suggest that three positive excursions and two negative excursions have been examined within the measured stratigraphical interval. Positive carbon isotope excursions occur separately in the lower part and the middle part of the Changhia Formation and in the upper part of the Chaumitien Formation, maximum δ13C values of these positive excursions reach to 2.0‰, 1.0‰ and 3.0‰ respectively. Negative δ13C excursions occur in the basal and the lower-middle part of the Changhia Formation with the minimum values of -3.4‰ and -1.0‰ respectively. Especially, the remarkable positive excursion examined in the upper part of the Chaumitien Formation commences on the base of the trilobite Chuangia zone, which corresponds to the base of the Paibian Stage in South China and is equivalent to the SPICE excursion detected in the Paibian Stage in USA, Australia, and Kazakhstan. The negative excursion examined in the basal part of the Changhia Formation is equivalent to the DICE excursion. Both the two carbon isotope excursions are not only used as tools for the regional stratigraphical classification and correlation, but also used as key indicators in defining the Drumian Stage and the Paibian Stage in North China. In addition, carbon isotope excursions are interpreted to be associated with global scale sea-level fluctuations, paleoecological environmental changes. Seawater transgression together with enlargement of paleoecological environment played an important role in positive carbon isotope excursions during the Late Miaolingian to the Early Furongian.
2020, 45(3): 739-751.
doi: 10.3799/dqkx.2019.028
Abstract:
Due to the lack of detailed division and comparison of graptolite biozonation in Wufeng and Longmaxi formations of Yongshan-Daguan area, the distribution time of black shale and its sedimentary background are unclear. Nine graptolite biozones of the Wufeng and Longmaxi formations are recognized in the Xindi 2 borehole from the Yongshan-Daguan area, NE Yunnan in this paper. They are Dicellograptus complanatus, D. complexus, P. pacificus-M. extraordinarius, A. ascensus-P. acuminatus, C. vesiculosus, C. cyphus, D. triangulatus, L. convolutes, and S. sedgwickii biozones. A correlation of the Wufeng-Longmaxi graptolite biozones among the Xingdi 2, Ning 211, Jiaoye 1, Wei 202, and Wuxi 2 boreholes are indicated. The top of the Longmaxi black shale is diachronous, from which the top of the Longmaxi black shale of the Xindi 2, Ning 211, and Jiaoye 1 boreholes are one biozone lower than those of the Wei 202 and Wuxi 2 boreholes. High TOC content in the Longmaxi black shale is measured from WF2 (D. complexus Biozone) to LM6 (D. triangulatus Biozone) in the Xindi 2 borehole but only up to LM 5 (C. cyphus Biozone) in the Ning 211 borehole near the Central Guizhou uplift. However, the top of the Longmaxi black shale in Wei 202 and Wuxi 2 boreholes may reach to the level of LM9 (S. guerichi Biozone).According to our study, the transgression to maximum flooding period is shortened near the uplift or the old land, and the upper limit of high-quality black shale can be as low as LM5 (or below). Sedimentary differentiation occurred in Weiyuan, Jiaoshiba and Wuxi areas, which was affected by sedimentary water depth and the debris input from the uplift.
Due to the lack of detailed division and comparison of graptolite biozonation in Wufeng and Longmaxi formations of Yongshan-Daguan area, the distribution time of black shale and its sedimentary background are unclear. Nine graptolite biozones of the Wufeng and Longmaxi formations are recognized in the Xindi 2 borehole from the Yongshan-Daguan area, NE Yunnan in this paper. They are Dicellograptus complanatus, D. complexus, P. pacificus-M. extraordinarius, A. ascensus-P. acuminatus, C. vesiculosus, C. cyphus, D. triangulatus, L. convolutes, and S. sedgwickii biozones. A correlation of the Wufeng-Longmaxi graptolite biozones among the Xingdi 2, Ning 211, Jiaoye 1, Wei 202, and Wuxi 2 boreholes are indicated. The top of the Longmaxi black shale is diachronous, from which the top of the Longmaxi black shale of the Xindi 2, Ning 211, and Jiaoye 1 boreholes are one biozone lower than those of the Wei 202 and Wuxi 2 boreholes. High TOC content in the Longmaxi black shale is measured from WF2 (D. complexus Biozone) to LM6 (D. triangulatus Biozone) in the Xindi 2 borehole but only up to LM 5 (C. cyphus Biozone) in the Ning 211 borehole near the Central Guizhou uplift. However, the top of the Longmaxi black shale in Wei 202 and Wuxi 2 boreholes may reach to the level of LM9 (S. guerichi Biozone).According to our study, the transgression to maximum flooding period is shortened near the uplift or the old land, and the upper limit of high-quality black shale can be as low as LM5 (or below). Sedimentary differentiation occurred in Weiyuan, Jiaoshiba and Wuxi areas, which was affected by sedimentary water depth and the debris input from the uplift.
2020, 45(3): 752-763.
doi: 10.3799/dqkx.2019.054
Abstract:
New dinosaur fossils were found from the Late Cretaceous Daijiaping Formation in the Zhuzhou Basin recently. However, the age of the dinosaur fossil formation remains controvercial. Based on the analysis of palynological types and detrital zircon U-Pb data, the age and geological background of the dinosaur fossils from the Tianyuan area, Zhuzhou City, Hunan Province, are reported here. 18 species of 15 genera of the main palynomorphs could obtain a concurrent-range Aquilapollenites coriaceus-Betpakdalina pentaoculoides zone. Through comparison of the typical palynomorphs from the Daijiaping Formation, the age of the formation can be accurately defined as Campanian-Maastrichtian. A series of detrital zircon samples are collected and analyzed from the key layers of dinosaur fossils, and the detrital zircon U-Pb age peaks can be divided into six stages: 200-320 Ma, 390-450 Ma, 740-950 Ma, 1 020-1 100 Ma, 1 640-2 000 Ma and 2 440-2 600 Ma. On the basis of detrital zircon and paleogeography analysis, coarse sediments of the Daijiaping Formation were mainly from the southeastern surrounding mountains, whereas parts of the fine-grained debris came from the northwestern Huangling area.
New dinosaur fossils were found from the Late Cretaceous Daijiaping Formation in the Zhuzhou Basin recently. However, the age of the dinosaur fossil formation remains controvercial. Based on the analysis of palynological types and detrital zircon U-Pb data, the age and geological background of the dinosaur fossils from the Tianyuan area, Zhuzhou City, Hunan Province, are reported here. 18 species of 15 genera of the main palynomorphs could obtain a concurrent-range Aquilapollenites coriaceus-Betpakdalina pentaoculoides zone. Through comparison of the typical palynomorphs from the Daijiaping Formation, the age of the formation can be accurately defined as Campanian-Maastrichtian. A series of detrital zircon samples are collected and analyzed from the key layers of dinosaur fossils, and the detrital zircon U-Pb age peaks can be divided into six stages: 200-320 Ma, 390-450 Ma, 740-950 Ma, 1 020-1 100 Ma, 1 640-2 000 Ma and 2 440-2 600 Ma. On the basis of detrital zircon and paleogeography analysis, coarse sediments of the Daijiaping Formation were mainly from the southeastern surrounding mountains, whereas parts of the fine-grained debris came from the northwestern Huangling area.
2020, 45(3): 764-775.
doi: 10.3799/dqkx.2019.076
Abstract:
Guanzhou Site, located beneath the surface of the central bar of Songzi reaches of the middle Yangtze River, which is the earliest and largest Neolithic cultural site found in the Jianghan Plain up to now. Since Guanzhou Site provides vital evidences for the prehistoric civilization in the middle Yangtze River, it is important to understand the relationship between geomorphological evolution and human development. Here, we use 14C dating and grain size characteristics analysis to investigate the sedimentary evolution history and constrain the drainage evolution of this region. We further discuss the causes of this site buried deep under the surface of Guanzhou Island. The chronology results show that the age of the Guanzhou Site is between 12 783 cal. a B.P. and Late 20th Century. The analytical results of grain size characteristics show that sediment deposited in the lower section (11.65-6.70 m) is fine, and the grain size changing tendency reflects the weak hydrodynamic and low-energy river sedimentary environment, which belongs to the floodplain bank accumulation. As for the middle (6.70-2.10 m) section, the coarse grain size layer and fine grain size layer occurred alternately, and the grain size curve shows the sedimentary environment changed between edge-floodplain deposition and strong hydrodynamic force, indicating that the site is in the condition of riverbed environment. The grain size characteristics of upper (2.10-0 m) section indicate it is a fine sediment layer, and the grain size curve reflects the river sedimentary environment as a weak and low energy hydrodynamic force, suggesting a floodplain accumulation. Based on the above analyses, the sedimentary evolution history and the middle Yangtze River channel evolution of the Guanzhou Site can be divided into three periods: The first period (11.65-6.70 m) is roughly from 12 783 cal. a B.P. to the Ming Dynasty or Qing Dynasty, when the former Guanzhou Island was still linked to the land, not an Island. The second period (6.70-2.10 m) is accumulation during the Ming Dynasty or Qing Dynasty, which exhibits a turbulent channel sedimentary environment. At that time, the Guanzhou Island was located on the concave bank of the river with strongly erosion. During the third period (2.10-0 m), the Guanzhou Island was finally formed as an island in the middle Yangtze River channel, separated from the land completely. From then on, the location of Guanzhou Island is similar to that of present-day, and the main channel of the Yangtze River in Songzi reaches changed to the south of the Guanzhou Island gradually.
Guanzhou Site, located beneath the surface of the central bar of Songzi reaches of the middle Yangtze River, which is the earliest and largest Neolithic cultural site found in the Jianghan Plain up to now. Since Guanzhou Site provides vital evidences for the prehistoric civilization in the middle Yangtze River, it is important to understand the relationship between geomorphological evolution and human development. Here, we use 14C dating and grain size characteristics analysis to investigate the sedimentary evolution history and constrain the drainage evolution of this region. We further discuss the causes of this site buried deep under the surface of Guanzhou Island. The chronology results show that the age of the Guanzhou Site is between 12 783 cal. a B.P. and Late 20th Century. The analytical results of grain size characteristics show that sediment deposited in the lower section (11.65-6.70 m) is fine, and the grain size changing tendency reflects the weak hydrodynamic and low-energy river sedimentary environment, which belongs to the floodplain bank accumulation. As for the middle (6.70-2.10 m) section, the coarse grain size layer and fine grain size layer occurred alternately, and the grain size curve shows the sedimentary environment changed between edge-floodplain deposition and strong hydrodynamic force, indicating that the site is in the condition of riverbed environment. The grain size characteristics of upper (2.10-0 m) section indicate it is a fine sediment layer, and the grain size curve reflects the river sedimentary environment as a weak and low energy hydrodynamic force, suggesting a floodplain accumulation. Based on the above analyses, the sedimentary evolution history and the middle Yangtze River channel evolution of the Guanzhou Site can be divided into three periods: The first period (11.65-6.70 m) is roughly from 12 783 cal. a B.P. to the Ming Dynasty or Qing Dynasty, when the former Guanzhou Island was still linked to the land, not an Island. The second period (6.70-2.10 m) is accumulation during the Ming Dynasty or Qing Dynasty, which exhibits a turbulent channel sedimentary environment. At that time, the Guanzhou Island was located on the concave bank of the river with strongly erosion. During the third period (2.10-0 m), the Guanzhou Island was finally formed as an island in the middle Yangtze River channel, separated from the land completely. From then on, the location of Guanzhou Island is similar to that of present-day, and the main channel of the Yangtze River in Songzi reaches changed to the south of the Guanzhou Island gradually.
2020, 45(3): 776-788.
doi: 10.3799/dqkx.2019.039
Abstract:
The Qushenla Formation is one of the most important volcanic strata in Bangong Co-Nujiang suture zone, however, there is no detailed geochronology and prospecting potential study. Based on long-term ore geological survey in Nima County, we do a detailed study on the Qushenla Formation in Reguole, Emengle, Aezuodeng areas, and date the dacite and andesite in Qushenla Formation with U-Pb age of zircons. They are 106.2±1.3 Ma and 107.7±1.4 Ma, respectively, as the result of Early Cretaceous magmatism. At the same time, good Cu, Au, Ag anomalies and one high-grade copper-bearing mineralized body were found in Aezuodeng and Emengle areas, according to the 1:50 000 stream sedimentary analysis. Given the regional metallogenic background, we suggest this area is a good prospecting target for porphyry-epithermal copper system exploration. The precise geochronology of Qeshenla Formation gives the direct evidence for the framework building of regional strata. The first discovery of the mineralization in Qushenla Formation reveals a new direction for the further exploration and prospecting in the large area of the Bangong Co-Nujiang suture zone covered volcanic rocks.
The Qushenla Formation is one of the most important volcanic strata in Bangong Co-Nujiang suture zone, however, there is no detailed geochronology and prospecting potential study. Based on long-term ore geological survey in Nima County, we do a detailed study on the Qushenla Formation in Reguole, Emengle, Aezuodeng areas, and date the dacite and andesite in Qushenla Formation with U-Pb age of zircons. They are 106.2±1.3 Ma and 107.7±1.4 Ma, respectively, as the result of Early Cretaceous magmatism. At the same time, good Cu, Au, Ag anomalies and one high-grade copper-bearing mineralized body were found in Aezuodeng and Emengle areas, according to the 1:50 000 stream sedimentary analysis. Given the regional metallogenic background, we suggest this area is a good prospecting target for porphyry-epithermal copper system exploration. The precise geochronology of Qeshenla Formation gives the direct evidence for the framework building of regional strata. The first discovery of the mineralization in Qushenla Formation reveals a new direction for the further exploration and prospecting in the large area of the Bangong Co-Nujiang suture zone covered volcanic rocks.
2020, 45(3): 789-803.
doi: 10.3799/dqkx.2019.044
Abstract:
Lithocap, as an important indicator for exploration, has not attracted widespread attention for a long time, hindering the exploration work.Three types of lithocaps related to different mineralization styles in Sinongduo area are sampled for petrology, microphysiography and whole rock geochemistry analysis in which Sinongduo red lithocaps correspond to Pb-Zn mineralization, while Woruo black lithocaps are of Au-Ag mineralization, and Maerdi white lithocaps display no obvious mineralization. Microscopic and petrological characteristics show that three types of lithocaps in the Sinongduo area have many quartz fragments which are composed of massive quartz and vuggy quartz. The whole rock geochemistry data show that Sinongduo red lithocaps contain over 90% of SiO2, and are mostly composed of quartz. The Pb contents are 288.75×10-6-4 769.16×10-6, and the Zn is 34.34×10-6-332.70×10-6. The Maerdi white lithocaps are rich in aluminosilicate minerals and show none metallogenic elements anomaly. The contents of K2O (0.26%-2.58%) in Woruo black lithocaps indicate that there are many potassium-rich altered minerals, and the contents of Au are 80.21×10-9-360.74×10-9. In conclusion, the forming processes of lithocaps can be explained as the ascending siliceous acid fluid reacting with the crystal tuff. Pb-Zn mineralization tends to result in enrichment of Be and a negative anomaly of Ce in chondrite normalized REE patterns. In contrast, Au-Ag mineralization benefits V, Rb, Mo and Cs and Ce, and there is a positive anomaly of Yb. In addition, the large amount of clay minerals in the biggest Maerdi white lithocap could be an implication for porphyry at depth.
Lithocap, as an important indicator for exploration, has not attracted widespread attention for a long time, hindering the exploration work.Three types of lithocaps related to different mineralization styles in Sinongduo area are sampled for petrology, microphysiography and whole rock geochemistry analysis in which Sinongduo red lithocaps correspond to Pb-Zn mineralization, while Woruo black lithocaps are of Au-Ag mineralization, and Maerdi white lithocaps display no obvious mineralization. Microscopic and petrological characteristics show that three types of lithocaps in the Sinongduo area have many quartz fragments which are composed of massive quartz and vuggy quartz. The whole rock geochemistry data show that Sinongduo red lithocaps contain over 90% of SiO2, and are mostly composed of quartz. The Pb contents are 288.75×10-6-4 769.16×10-6, and the Zn is 34.34×10-6-332.70×10-6. The Maerdi white lithocaps are rich in aluminosilicate minerals and show none metallogenic elements anomaly. The contents of K2O (0.26%-2.58%) in Woruo black lithocaps indicate that there are many potassium-rich altered minerals, and the contents of Au are 80.21×10-9-360.74×10-9. In conclusion, the forming processes of lithocaps can be explained as the ascending siliceous acid fluid reacting with the crystal tuff. Pb-Zn mineralization tends to result in enrichment of Be and a negative anomaly of Ce in chondrite normalized REE patterns. In contrast, Au-Ag mineralization benefits V, Rb, Mo and Cs and Ce, and there is a positive anomaly of Yb. In addition, the large amount of clay minerals in the biggest Maerdi white lithocap could be an implication for porphyry at depth.
2020, 45(3): 804-814.
doi: 10.3799/dqkx.2019.029
Abstract:
The single-collector noble gas mass spectrometer has constrained the further development of the high-precision 40Ar-39Ar dating, owing to its relatively low efficiency and precision of measurement. However, the multi-collector noble gas mass spectrometer has been increasingly widely applied in the high-precision 40Ar-39Ar dating in recent years, showing great advantage and potentiality. The method of 40Ar-39Ar dating by laser total fusion/stepwise heating using the multi-collector noble gas mass spectrometer Argus Ⅵ is reported briefly, and the measurements of air, standard mineral FCs and YBCs, and the K-feldspar from the Kaimuqi granitic pluton in the East Kunlun were performed. Concordant atmospheric 40Ar/36Ar ratio and the corresponding mass discrimination factor (MDF) were obtained from 326 air argon analyses during four successive months, indicative of the stability of the machine system. The "model ages" calculated from the laser fusion 40Ar-39Ar results of FCs and YBCs suggest that, the level of precision achievable using the Argus Ⅵ for single-grain or minor sample analysis is significantly high and is better than 1‰ (excluding the errors associated with the age of monitors and decay constants). J value and F value (40Ar*/39ArK) calculated from the total fusion results of the FCs show similar trend with those from ARGONAUT lab at the University of Salzburg, both suggesting a distinct gradient of the neutron flux of the LVR-15 reactor. The intercalibration factor between YBCs and FCs based on our total fusion analysis of YCs are calculated as: RFCsYBCs=1.045 304±0.000 752 (1σ), and the single-grain total fusion age of 29.280±0.086 (1σ) for YBCs is obtained as well. The results are in good agreement with those of previous studies within the range of uncertainty. Stepwise heating analyses of the K-feldspar from the Kaimuqi granitic pluton in the East Kunlun yield a plateau age of 229.9±0.2 Ma (1σ, MSWD=1.59), and an inverse isochron age of 229.8±0.4 Ma, MSWD=1.71). In combination with published geochronology data of zircon U-Pb, and biotite and K-feldspar 40Ar-39Ar in this area, it is suggested that the 40Ar-39Ar age of the K-feldspar from the Kaimuqi granitic pluton represents a rapid cooling-exhumation event in the East Kunlun during Late Triassic.
The single-collector noble gas mass spectrometer has constrained the further development of the high-precision 40Ar-39Ar dating, owing to its relatively low efficiency and precision of measurement. However, the multi-collector noble gas mass spectrometer has been increasingly widely applied in the high-precision 40Ar-39Ar dating in recent years, showing great advantage and potentiality. The method of 40Ar-39Ar dating by laser total fusion/stepwise heating using the multi-collector noble gas mass spectrometer Argus Ⅵ is reported briefly, and the measurements of air, standard mineral FCs and YBCs, and the K-feldspar from the Kaimuqi granitic pluton in the East Kunlun were performed. Concordant atmospheric 40Ar/36Ar ratio and the corresponding mass discrimination factor (MDF) were obtained from 326 air argon analyses during four successive months, indicative of the stability of the machine system. The "model ages" calculated from the laser fusion 40Ar-39Ar results of FCs and YBCs suggest that, the level of precision achievable using the Argus Ⅵ for single-grain or minor sample analysis is significantly high and is better than 1‰ (excluding the errors associated with the age of monitors and decay constants). J value and F value (40Ar*/39ArK) calculated from the total fusion results of the FCs show similar trend with those from ARGONAUT lab at the University of Salzburg, both suggesting a distinct gradient of the neutron flux of the LVR-15 reactor. The intercalibration factor between YBCs and FCs based on our total fusion analysis of YCs are calculated as: RFCsYBCs=1.045 304±0.000 752 (1σ), and the single-grain total fusion age of 29.280±0.086 (1σ) for YBCs is obtained as well. The results are in good agreement with those of previous studies within the range of uncertainty. Stepwise heating analyses of the K-feldspar from the Kaimuqi granitic pluton in the East Kunlun yield a plateau age of 229.9±0.2 Ma (1σ, MSWD=1.59), and an inverse isochron age of 229.8±0.4 Ma, MSWD=1.71). In combination with published geochronology data of zircon U-Pb, and biotite and K-feldspar 40Ar-39Ar in this area, it is suggested that the 40Ar-39Ar age of the K-feldspar from the Kaimuqi granitic pluton represents a rapid cooling-exhumation event in the East Kunlun during Late Triassic.
2020, 45(3): 815-828.
doi: 10.3799/dqkx.2019.062
Abstract:
The East Qinling Mountains, located at the junction of the Qinling Orogenic Belt and the Dabie Orogenic Belt, had undergone complex tectonic evolution, and plays an important role in understanding the collision of the North China Block and the Yangtze Block. The Nanwan Formation plays an important role in understanding the tectonic process of the East Qinling Mountains, however, few studies have been done to analyze the regional differences in material composition. In this paper, the LA-ICP-MS U-Pb geochronology analyses of the detrital zircons from the Nanwan Formation in the Wanghuolou, Zhenping County, East Qinling, show that the zircon age peaks are mainly concentrated in 2 757-2 500 Ma, 2 500-2 400 Ma, 2 150-1 800 Ma, 1 800-1 700 Ma, 1 520-1 165 Ma, 1 100-1 000 Ma, 1 000-880 Ma, 840-630 Ma and 550-471 Ma, respectively. The original rock material is mainly from the North China Block and the North Qinling Orogenic Belt and South Qinling Orogenic Belt. There are some differences among the age peaks and material composition of the Nanwan Formation in Zhenping County, the Liuling Group in the Qinling Mountains, the Nanwan Formation in the Xinyang area, and the Foziling Group in the North Dabie Orogenic Belt. Therefore, further studies should be carried out to evaluate whether the four can be compared.
The East Qinling Mountains, located at the junction of the Qinling Orogenic Belt and the Dabie Orogenic Belt, had undergone complex tectonic evolution, and plays an important role in understanding the collision of the North China Block and the Yangtze Block. The Nanwan Formation plays an important role in understanding the tectonic process of the East Qinling Mountains, however, few studies have been done to analyze the regional differences in material composition. In this paper, the LA-ICP-MS U-Pb geochronology analyses of the detrital zircons from the Nanwan Formation in the Wanghuolou, Zhenping County, East Qinling, show that the zircon age peaks are mainly concentrated in 2 757-2 500 Ma, 2 500-2 400 Ma, 2 150-1 800 Ma, 1 800-1 700 Ma, 1 520-1 165 Ma, 1 100-1 000 Ma, 1 000-880 Ma, 840-630 Ma and 550-471 Ma, respectively. The original rock material is mainly from the North China Block and the North Qinling Orogenic Belt and South Qinling Orogenic Belt. There are some differences among the age peaks and material composition of the Nanwan Formation in Zhenping County, the Liuling Group in the Qinling Mountains, the Nanwan Formation in the Xinyang area, and the Foziling Group in the North Dabie Orogenic Belt. Therefore, further studies should be carried out to evaluate whether the four can be compared.
2020, 45(3): 829-843.
doi: 10.3799/dqkx.2020.001
Abstract:
Zhiluo Formation is located in Tarangaole area of the Ordos Basin and the research on the provenance and regional sedimentary structural setting remains weak, which restricts the overall evaluation of provenance change of Zhiluo Formationto some extent. Geochemical analysis and zircon U-Pb dating of sandstone in the lower Zhiluo Formation of uranium bearing horizon in Tarangaole area are applied in this paper. The results show that source rocks of the lower part of Zhiluo Formation are mainly felsic sedimentary rocks and few neutral magmatic rocks, and the tectonic setting of which is the active continental margin-continental margin arc environment. Based on the characteristics of trace and rare earth elements and zircon U-Pb dating results, it is considered that the sources of Zhiluo Formation in study area are mainly from Konzite, TTG gneiss, granulite and mafic-ultramafic layered intrusive rocks in Daqingshan-Wulashan area, and Variscan-Indosinian-Yanshanian period magmatic rocks of Yinshan area. The distribution of sandstones in the lower part of Zhiluo Formation clearly reflects the direction of source supply from north to south, the discovery of Triassic detrital zircons indicates that the Indosinian intrusive rocks have been uplifted bare surface to provide material source during the sedimentation of the lower part of Zhiluo Formation in Triassic, and the proportion of younger provenance components in the upper member is higher than that in the lower member of the lower part of Zhiluo Formation.
Zhiluo Formation is located in Tarangaole area of the Ordos Basin and the research on the provenance and regional sedimentary structural setting remains weak, which restricts the overall evaluation of provenance change of Zhiluo Formationto some extent. Geochemical analysis and zircon U-Pb dating of sandstone in the lower Zhiluo Formation of uranium bearing horizon in Tarangaole area are applied in this paper. The results show that source rocks of the lower part of Zhiluo Formation are mainly felsic sedimentary rocks and few neutral magmatic rocks, and the tectonic setting of which is the active continental margin-continental margin arc environment. Based on the characteristics of trace and rare earth elements and zircon U-Pb dating results, it is considered that the sources of Zhiluo Formation in study area are mainly from Konzite, TTG gneiss, granulite and mafic-ultramafic layered intrusive rocks in Daqingshan-Wulashan area, and Variscan-Indosinian-Yanshanian period magmatic rocks of Yinshan area. The distribution of sandstones in the lower part of Zhiluo Formation clearly reflects the direction of source supply from north to south, the discovery of Triassic detrital zircons indicates that the Indosinian intrusive rocks have been uplifted bare surface to provide material source during the sedimentation of the lower part of Zhiluo Formation in Triassic, and the proportion of younger provenance components in the upper member is higher than that in the lower member of the lower part of Zhiluo Formation.
2020, 45(3): 844-855.
doi: 10.3799/dqkx.2020.006
Abstract:
The precise chronology and tectonic significance of pyroxene peridotite in Late Paleozoic granites in Dong Ujimqi, Inner Mongolia are still unclear, which will directly restrict the discussion of the properties and tectonic evolution in the study area. In this paper, petrography analysis, geochemistry and zircon U-Pb dating for the newly discovered pyroxene peridotite were studied. The analysis results show that main rock forming minerals are olivine, hornblende, orthopyroxene, and small amounts of plagioclase, biotite and clinopyroxene. The weighted average age obtained is 317.8±1.6 Ma, indicating that the intrusion was formed in the Late Carboniferous. Geochemical data show that, samples have SiO2 content of 40.28%-44.50%, MgO content of 23.42%-29.44% and Na2O+K2O content of 1.00%-2.12%, have low m/f ratio (3.13-3.86), high FeOT content (11.18%-14.70%) and Mg# (75.60-79.26), and belong to the series of ferrous ultramafic rocks and tholeiites. These rocks have high REE (31.98×10-6-72.60×10-6), enrichment in LREE and relatively depletion in HREE, (La/Yb)N=3.56-7.72, slightly Eu anomalies (δEu=0.79-1.65).The standardized distribution pattern of REE chondrites is right-leaning. The rocks are enriched in LILE (Rb, Sr, K) and depleted in HFSE (Nb, Ta), and there are obvious negative anomalies of Nb, Ta and Ti. Thus, we consider that the pyroxene peridotite had been formed in extensional tectonics from partial melting of the Sp-peridotite, which was modified by the subducted slab-derived fluid.
The precise chronology and tectonic significance of pyroxene peridotite in Late Paleozoic granites in Dong Ujimqi, Inner Mongolia are still unclear, which will directly restrict the discussion of the properties and tectonic evolution in the study area. In this paper, petrography analysis, geochemistry and zircon U-Pb dating for the newly discovered pyroxene peridotite were studied. The analysis results show that main rock forming minerals are olivine, hornblende, orthopyroxene, and small amounts of plagioclase, biotite and clinopyroxene. The weighted average age obtained is 317.8±1.6 Ma, indicating that the intrusion was formed in the Late Carboniferous. Geochemical data show that, samples have SiO2 content of 40.28%-44.50%, MgO content of 23.42%-29.44% and Na2O+K2O content of 1.00%-2.12%, have low m/f ratio (3.13-3.86), high FeOT content (11.18%-14.70%) and Mg# (75.60-79.26), and belong to the series of ferrous ultramafic rocks and tholeiites. These rocks have high REE (31.98×10-6-72.60×10-6), enrichment in LREE and relatively depletion in HREE, (La/Yb)N=3.56-7.72, slightly Eu anomalies (δEu=0.79-1.65).The standardized distribution pattern of REE chondrites is right-leaning. The rocks are enriched in LILE (Rb, Sr, K) and depleted in HFSE (Nb, Ta), and there are obvious negative anomalies of Nb, Ta and Ti. Thus, we consider that the pyroxene peridotite had been formed in extensional tectonics from partial melting of the Sp-peridotite, which was modified by the subducted slab-derived fluid.
2020, 45(3): 856-868.
doi: 10.3799/dqkx.2019.061
Abstract:
In recent years, in situ U-Pb dating of garnet is a newly developed isotopic dating method about the low-U minerals, yet it has been scarcely applied in the ore deposits and especially in the nonmetal deposits. Based on detailed petrographic observations, two generation of garnets have been distinguished from the Gaojiashan Wo(-Cu) deposit in Southeast Hubei Province, namely the first generational garnet (Grt1) with dark-brown color and the second generational garnet (Grt2) with light-brown color. Electron probe composition analysis (EMPA) shows that both of them belong to andradite to grossularite solid solution series, in which Grt1 is relatively rich in Fe (Adr62.4Gro36.5 to Adr94.4Gro0), while Grt2 is relatively rich in Al (Adr32.6Gro66.4 to Adr40.2Gro58.6). LA-ICP-MS U-Pb dating on Grt1 and Grt2 yield Tera-Wasserburg lower intercept 206Pb/238U age of 142.5±2.0 Ma (2σ, MSWD=1.30, n=38) and 136.0±14.0 Ma (2σ, MSWD=0.42, n=17), which is consistent with the weighted mean 206Pb/238U ages (139.8±1.5 Ma; 2σ, MSWD=0.10, n=22) of zircon in the quartz monzodiorite at Gaoyishan within the error range, indicating a close genetic relationship between them. The Grt1 with high U concentration and low common Pb content are the major factors for the success of U-Pb isotopic dating.
In recent years, in situ U-Pb dating of garnet is a newly developed isotopic dating method about the low-U minerals, yet it has been scarcely applied in the ore deposits and especially in the nonmetal deposits. Based on detailed petrographic observations, two generation of garnets have been distinguished from the Gaojiashan Wo(-Cu) deposit in Southeast Hubei Province, namely the first generational garnet (Grt1) with dark-brown color and the second generational garnet (Grt2) with light-brown color. Electron probe composition analysis (EMPA) shows that both of them belong to andradite to grossularite solid solution series, in which Grt1 is relatively rich in Fe (Adr62.4Gro36.5 to Adr94.4Gro0), while Grt2 is relatively rich in Al (Adr32.6Gro66.4 to Adr40.2Gro58.6). LA-ICP-MS U-Pb dating on Grt1 and Grt2 yield Tera-Wasserburg lower intercept 206Pb/238U age of 142.5±2.0 Ma (2σ, MSWD=1.30, n=38) and 136.0±14.0 Ma (2σ, MSWD=0.42, n=17), which is consistent with the weighted mean 206Pb/238U ages (139.8±1.5 Ma; 2σ, MSWD=0.10, n=22) of zircon in the quartz monzodiorite at Gaoyishan within the error range, indicating a close genetic relationship between them. The Grt1 with high U concentration and low common Pb content are the major factors for the success of U-Pb isotopic dating.
2020, 45(3): 869-879.
doi: 10.3799/dqkx.2019.064
Abstract:
Large-scale Mesozoic magmatic rocks developed in the Benxi-Kuandian area in central eastern Liaoning Province. However, research on the formation age, magmatic source, and tectonic setting of these rocks relatively lags behind. Guanmenshan pluton is mainly composed of granite porphyry and alkali-feldspar granite, and its petrology, petrogeochemistry and chronology have been studied. LA-ICP-MS zircon U-Pb dating indicates that the emplacement age of the granite porphyry is 126.4±1.5 Ma, the emplacement age of the alkali-feldspar granite is 125.7±1.7 Ma, and that the pluton was emplaced in Early Cretaceous. The major elements of the granite porphyry and the alkali-feldspar granite are high in Si and K, and low in Fe, Mg, Ca and Ti, A/CNK=0.95-1.12. Trace elements are enriched in incompatible elements such as K, Rb, Th and depleted in Ba, Sr, Ti and P, with evident negative Eu anomalies, (La/Yb)N=7.62-17.32, and high field strength elements. These features suggest that the Guanmenshan pluton belongs to A-type granite. Combined with geochemical characteristics, the Guanmenshan pluton is the product of magmatism in the extensional tectonic setting, which was controlled by the subduction of Izanagi Plate to Eurasia Plate in the lithosphere thinning environment. It is considered a concrete manifestation of the eastern North China Plate stretch geodynamic setting.
Large-scale Mesozoic magmatic rocks developed in the Benxi-Kuandian area in central eastern Liaoning Province. However, research on the formation age, magmatic source, and tectonic setting of these rocks relatively lags behind. Guanmenshan pluton is mainly composed of granite porphyry and alkali-feldspar granite, and its petrology, petrogeochemistry and chronology have been studied. LA-ICP-MS zircon U-Pb dating indicates that the emplacement age of the granite porphyry is 126.4±1.5 Ma, the emplacement age of the alkali-feldspar granite is 125.7±1.7 Ma, and that the pluton was emplaced in Early Cretaceous. The major elements of the granite porphyry and the alkali-feldspar granite are high in Si and K, and low in Fe, Mg, Ca and Ti, A/CNK=0.95-1.12. Trace elements are enriched in incompatible elements such as K, Rb, Th and depleted in Ba, Sr, Ti and P, with evident negative Eu anomalies, (La/Yb)N=7.62-17.32, and high field strength elements. These features suggest that the Guanmenshan pluton belongs to A-type granite. Combined with geochemical characteristics, the Guanmenshan pluton is the product of magmatism in the extensional tectonic setting, which was controlled by the subduction of Izanagi Plate to Eurasia Plate in the lithosphere thinning environment. It is considered a concrete manifestation of the eastern North China Plate stretch geodynamic setting.
2020, 45(3): 880-891.
doi: 10.3799/dqkx.2019.103
Abstract:
The Precambrian-Cambrian transition is one of the most important periods in the geological history. Establishing precise stratigraphic correlations among different sedimentary facies lays the foundation for deciphering important geological events including the Cambrian Explosion. LA-ICP-MS U-Pb zircon geochronology was carried out for the two tuffs in the upmost Doushantuo Formation and the basal Liuchapo Formation at the Yangtou section, Guizhou Province in this study. The weighted mean ages of the two tuffs are 554.2±3.3 Ma and 550.6±3.3 Ma, respectively. The new data suggests that the deposition time of the Liuchapo Formation in the deep-water facies of the Yangtze Platform is about 550 Ma. During the Ediacaran-Cambrian transition, the distinct differentiation of deposite facies across the Yangtze Platform indicates that the Yangtze Platform turned into extensional setting during this period. Therefore, the age of 550.6±3.3 Ma at the basal Liuchapo Formation also represents the time when the Yangtze Platform turned into the extensional setting and intense hydrothermal activities. In addition, trace elements of zircons indicate that the two tuffs derived from granite which formed in the magmatic arc or the orogenic environment.
The Precambrian-Cambrian transition is one of the most important periods in the geological history. Establishing precise stratigraphic correlations among different sedimentary facies lays the foundation for deciphering important geological events including the Cambrian Explosion. LA-ICP-MS U-Pb zircon geochronology was carried out for the two tuffs in the upmost Doushantuo Formation and the basal Liuchapo Formation at the Yangtou section, Guizhou Province in this study. The weighted mean ages of the two tuffs are 554.2±3.3 Ma and 550.6±3.3 Ma, respectively. The new data suggests that the deposition time of the Liuchapo Formation in the deep-water facies of the Yangtze Platform is about 550 Ma. During the Ediacaran-Cambrian transition, the distinct differentiation of deposite facies across the Yangtze Platform indicates that the Yangtze Platform turned into extensional setting during this period. Therefore, the age of 550.6±3.3 Ma at the basal Liuchapo Formation also represents the time when the Yangtze Platform turned into the extensional setting and intense hydrothermal activities. In addition, trace elements of zircons indicate that the two tuffs derived from granite which formed in the magmatic arc or the orogenic environment.
2020, 45(3): 892-909.
doi: 10.3799/dqkx.2019.022
Abstract:
The Early Paleozoic orogen in South China is an intraplate orogen and represented by the Wuyi-Yunkai Orogenic Belt (WYOB). However,the nature of lithospheric mantle and tectonic setting during this orogenic process have been controversial. We present here,for the first time,geochronological,isotopic and geochemical data for the Hebaoshan diabase dike in Taining area,central WYOB. LA-ICP-MS dating on zircon of the Hebaoshan diabase dike yields an age of 430±3 Ma,suggesting the formation time of Middle Silurian. Seven samples possess high Al2O3(15.23%-18.49%) and low Na2O(2.82%-4.21%),K2O (1.63%-2.42%) contents,belonging to subalkaline rocks. The REE patterns show a negative slope due to LREE enrichment with insignificant Eu anomalies. Diabase is characterized by enrichment in Rb,Ba,K,La,Sr while depletion in Ta,U,Hf and Ti,relative to the primitive mantle. The high Nb(5.74×10-6-8.45×10-6) content,together with high values of (Nb/La)N and Nb/U,coincides with those of typical Nb-rich Island Arc Basalt. The Hebaoshan diabase dike,with variable εNd(t) values (-0.8—-0.1),εHf(t) values (-9.2—-2.7) and two-stage Hf model ages (T2DM(Hf)=1.4-1.8 Ga),was probably derived from the partial melting (13.3%~21.8%) of previously subduction-modified lithospheric mantle in the garnet-spinel olives facies and was likely formed in an intracontinental post-orogenic collapse regime related to a far-field effect from Eastern Gondwana orogeny.
The Early Paleozoic orogen in South China is an intraplate orogen and represented by the Wuyi-Yunkai Orogenic Belt (WYOB). However,the nature of lithospheric mantle and tectonic setting during this orogenic process have been controversial. We present here,for the first time,geochronological,isotopic and geochemical data for the Hebaoshan diabase dike in Taining area,central WYOB. LA-ICP-MS dating on zircon of the Hebaoshan diabase dike yields an age of 430±3 Ma,suggesting the formation time of Middle Silurian. Seven samples possess high Al2O3(15.23%-18.49%) and low Na2O(2.82%-4.21%),K2O (1.63%-2.42%) contents,belonging to subalkaline rocks. The REE patterns show a negative slope due to LREE enrichment with insignificant Eu anomalies. Diabase is characterized by enrichment in Rb,Ba,K,La,Sr while depletion in Ta,U,Hf and Ti,relative to the primitive mantle. The high Nb(5.74×10-6-8.45×10-6) content,together with high values of (Nb/La)N and Nb/U,coincides with those of typical Nb-rich Island Arc Basalt. The Hebaoshan diabase dike,with variable εNd(t) values (-0.8—-0.1),εHf(t) values (-9.2—-2.7) and two-stage Hf model ages (T2DM(Hf)=1.4-1.8 Ga),was probably derived from the partial melting (13.3%~21.8%) of previously subduction-modified lithospheric mantle in the garnet-spinel olives facies and was likely formed in an intracontinental post-orogenic collapse regime related to a far-field effect from Eastern Gondwana orogeny.
2020, 45(3): 910-929.
doi: 10.3799/dqkx.2019.070
Abstract:
The Yinshuisi Zn-Pb deposit,located in the north border of Dabie Orogen Belt,Jinzhai County,Anhui Province,is the largest skarn deposit in the Dabieshan region. Previous studies on chronology,geochemistry and petrogenesis of intrusions are few,which has restricted the understanding of lead-zinc metallogenic regularity. Detailed geochronology,geochemistry,and isotopic data for ore-related syeno-granite were analyzed in this study.LA-ICP-MS U-Pb dating of zircon from Yinshuisi syeno-granite porphyry yields age of 125.4±0.4 Ma,suggesting that it resulted from Early Cretaceous magmatism.According to the geochemical analysis,Yinshuisi syeno-granite porphyry has high SiO2 (71.43%-72.71%),K2O (4.62%-4.88%) and ALK (K2O+Na2O=7.47%-7.81%),but weakly peraluminous (A/CNK=1.03-1.06). The rock is enriched in Fe,Rb,Th,U and LREE,depleted in Ca,Sr,Ba,Ti,P and HREE with negative Eu anomalies,which indicates that Yinshuisi syeno-granite porphyry belongs to aluminous A-type granite.The Yinshuisi syeno-granite porphyry has highly enriched Sr-Nd-Hf isotopic compositions: (87Sr/86Sr)i=0.710 21-0.710 53,εNd(t)=-20.0—-19.2. The εHf(t) value ranges from -26.7 to -23.8,lying below the depleted mantle line.The TDM2 value ranges from 2 663 Ma to 2 845 Ma,which indicates that the syeno-granite porphyry derived from dominantly the mixing of Yangtze's lower crust with the Dabie Complex. Yinshuisi syeno-granite porphyry was emplaced after the major collisional period of the North China Block and Yangtze Block,in a post-collisional or intracontinental extensional setting under the regional extension mechanism,which has the capacity to cause the regional upwelling of the asthenospheric mantle. The thinned lithospheric mantle was exposed to the upwelling asthenopsheric mantle,leading to intensive magmatism,which was related to the rollback of westward subducting Paleo-Pacific Plate beneath the Asian continent.
The Yinshuisi Zn-Pb deposit,located in the north border of Dabie Orogen Belt,Jinzhai County,Anhui Province,is the largest skarn deposit in the Dabieshan region. Previous studies on chronology,geochemistry and petrogenesis of intrusions are few,which has restricted the understanding of lead-zinc metallogenic regularity. Detailed geochronology,geochemistry,and isotopic data for ore-related syeno-granite were analyzed in this study.LA-ICP-MS U-Pb dating of zircon from Yinshuisi syeno-granite porphyry yields age of 125.4±0.4 Ma,suggesting that it resulted from Early Cretaceous magmatism.According to the geochemical analysis,Yinshuisi syeno-granite porphyry has high SiO2 (71.43%-72.71%),K2O (4.62%-4.88%) and ALK (K2O+Na2O=7.47%-7.81%),but weakly peraluminous (A/CNK=1.03-1.06). The rock is enriched in Fe,Rb,Th,U and LREE,depleted in Ca,Sr,Ba,Ti,P and HREE with negative Eu anomalies,which indicates that Yinshuisi syeno-granite porphyry belongs to aluminous A-type granite.The Yinshuisi syeno-granite porphyry has highly enriched Sr-Nd-Hf isotopic compositions: (87Sr/86Sr)i=0.710 21-0.710 53,εNd(t)=-20.0—-19.2. The εHf(t) value ranges from -26.7 to -23.8,lying below the depleted mantle line.The TDM2 value ranges from 2 663 Ma to 2 845 Ma,which indicates that the syeno-granite porphyry derived from dominantly the mixing of Yangtze's lower crust with the Dabie Complex. Yinshuisi syeno-granite porphyry was emplaced after the major collisional period of the North China Block and Yangtze Block,in a post-collisional or intracontinental extensional setting under the regional extension mechanism,which has the capacity to cause the regional upwelling of the asthenospheric mantle. The thinned lithospheric mantle was exposed to the upwelling asthenopsheric mantle,leading to intensive magmatism,which was related to the rollback of westward subducting Paleo-Pacific Plate beneath the Asian continent.
2020, 45(3): 930-944.
doi: 10.3799/dqkx.2019.983
Abstract:
The ore exploration of Demingding mining area of the Gangdese metallogenic belt has been challenging due to inconvenient transportation,high altitude and lack of oxygen,strong physical weathering and cover of the crushed stone. In order to further guide the field mineral exploration,we carried out systematic short-wave infrared spectroscopy analysis based on detailed field observation and cataloging. The scalars of sericite minerals in the short-wave infrared spectrum show a regular change in space. From the concentration center to periphery,the absorption peak wavelength of the Al-OH (Pos2200) gradually becomes longer,the depth of the Al-OH absorption peak (Dep2200) gradually decreases,and the SWIR-IC value gradually becomes smaller. And the three zones are well fitted,which indicates that the temperature of the altered sericite minerals formation is higher and the pressure is higher in the region. Combined with the zircon U-Pb age and the molybdenite Re-Os isotopic age in the ore-forming rocks,we estimate an exploration target area in the mining area where the late copper mineralization overlaps with the early (copper) molybdenum mineralization. Short-wave infrared spectroscopy can quickly and effectively guide mineral exploration and reduce exploration costs. Therefore,it can be used as one of the important methods for prospecting and evaluation of western special landscape areas.
The ore exploration of Demingding mining area of the Gangdese metallogenic belt has been challenging due to inconvenient transportation,high altitude and lack of oxygen,strong physical weathering and cover of the crushed stone. In order to further guide the field mineral exploration,we carried out systematic short-wave infrared spectroscopy analysis based on detailed field observation and cataloging. The scalars of sericite minerals in the short-wave infrared spectrum show a regular change in space. From the concentration center to periphery,the absorption peak wavelength of the Al-OH (Pos2200) gradually becomes longer,the depth of the Al-OH absorption peak (Dep2200) gradually decreases,and the SWIR-IC value gradually becomes smaller. And the three zones are well fitted,which indicates that the temperature of the altered sericite minerals formation is higher and the pressure is higher in the region. Combined with the zircon U-Pb age and the molybdenite Re-Os isotopic age in the ore-forming rocks,we estimate an exploration target area in the mining area where the late copper mineralization overlaps with the early (copper) molybdenum mineralization. Short-wave infrared spectroscopy can quickly and effectively guide mineral exploration and reduce exploration costs. Therefore,it can be used as one of the important methods for prospecting and evaluation of western special landscape areas.
2020, 45(3): 945-959.
doi: 10.3799/dqkx.2019.057
Abstract:
The Jinchiling gold deposit,located in the central and western part of Zhaoyuan-Laizhou gold metallogenic belt,is a typical lode gold deposit hosted in Late Jurassic Linglong granitoids in the Jiaodong region. The source of its ore-forming fluids and ore genesis,however,are still in debate. Based on the detailed study of mineralogy and microstructure of pyrite,trace elements and sulfur isotopes of gold bearing pyrite are analyzed by LA-(MC)-ICP-MS to constrain the source of ore-forming fluids and ore genesis. Two types (PyI and PyII) of gold-bearing pyrite can be identified. PyI is hosted in the quartz-pyrite stage,and PyII occurs in the quartz-polymetallic sulfide stage,which is associated with abundant visible gold. BSE images show that PyII commonly has core-rim texture. The PyIIa core contains many sulfide inclusions,whereas PyIIb rim is relatively clean. LA-ICP-MS analyses show that PyI contains medium contents of Au (< 0.015×10-6-2.18×10-6,mean 0.62×10-6) and As (78.98×10-6-857×10-6,mean 542×10-6),but very low contents of other metal elements (Pb and Zn). PyIIa has trace elements similar to those of PyI,but lower Au (< 0.015×10-6-0.59×10-6,mean 0.11×10-6) and As (0.62×10-6-198×10-6,mean 35.81×10-6). However,PyIIb has significantly high Au (< 0.015×10-6-19.71×10-6,mean 5.91×10-6) and As (399×10-6-18 153×10-6,mean 6 412×10-6),which shows a positive correlation. In addition,PyI and PyIIa have consistent in situ δ34S values,ranging from 3.0‰ to 4.9‰,whereas PyIIb is higher (5.2‰-6.6‰). Our data thus suggest that a new pulse of Au-As enriched ore-formed fluids were input into the mineralizing vein system during quartz-polymetallic sulfide stage,inducing the metasomatism of PyIIa and deposition of abundant visible gold. Our study hence implies that multiple phases of ore-forming fluids may be involved in the formation of high-grade lode gold deposits in Jiaodong.
The Jinchiling gold deposit,located in the central and western part of Zhaoyuan-Laizhou gold metallogenic belt,is a typical lode gold deposit hosted in Late Jurassic Linglong granitoids in the Jiaodong region. The source of its ore-forming fluids and ore genesis,however,are still in debate. Based on the detailed study of mineralogy and microstructure of pyrite,trace elements and sulfur isotopes of gold bearing pyrite are analyzed by LA-(MC)-ICP-MS to constrain the source of ore-forming fluids and ore genesis. Two types (PyI and PyII) of gold-bearing pyrite can be identified. PyI is hosted in the quartz-pyrite stage,and PyII occurs in the quartz-polymetallic sulfide stage,which is associated with abundant visible gold. BSE images show that PyII commonly has core-rim texture. The PyIIa core contains many sulfide inclusions,whereas PyIIb rim is relatively clean. LA-ICP-MS analyses show that PyI contains medium contents of Au (< 0.015×10-6-2.18×10-6,mean 0.62×10-6) and As (78.98×10-6-857×10-6,mean 542×10-6),but very low contents of other metal elements (Pb and Zn). PyIIa has trace elements similar to those of PyI,but lower Au (< 0.015×10-6-0.59×10-6,mean 0.11×10-6) and As (0.62×10-6-198×10-6,mean 35.81×10-6). However,PyIIb has significantly high Au (< 0.015×10-6-19.71×10-6,mean 5.91×10-6) and As (399×10-6-18 153×10-6,mean 6 412×10-6),which shows a positive correlation. In addition,PyI and PyIIa have consistent in situ δ34S values,ranging from 3.0‰ to 4.9‰,whereas PyIIb is higher (5.2‰-6.6‰). Our data thus suggest that a new pulse of Au-As enriched ore-formed fluids were input into the mineralizing vein system during quartz-polymetallic sulfide stage,inducing the metasomatism of PyIIa and deposition of abundant visible gold. Our study hence implies that multiple phases of ore-forming fluids may be involved in the formation of high-grade lode gold deposits in Jiaodong.
2020, 45(3): 960-967.
doi: 10.3799/dqkx.2019.072
Abstract:
As one of the most important elements of the loess in southern China,the provenance of "Wushan Loess" can provide crucial environmental information to deciphering valuable sedimentary record in the area. Based on previous studies,we have collected samples from "Wushan Loess" profile and carried out Sr-Nd isotope analysis,and compared with sediments synchronous to Loess Plateau and fluvial sediments with nearby provenance. The results show that the variation range of 87Sr/86Sr of "Wushan Loess" is 0.717 411-0.719 163 with an average value of 0.717 998,which is almost identical with the 87Sr/86Sr values of Loess Plateau during the last glacial period (variation range is 0.718 235 to 0.719 673,average is 0.718 623).The value of εNd(0) of "Wushan Loess" loess ranges from -10.1 to -11.7 with an average value of -11.4,which is quite different from the value of εNd(0) (-5.9 to -7.2) of modern floodplain sediments in the upper reaches of the Yangtze River,is close to that of Loess Plateau (-9.2 to -11.3). Our research shows that the dust of "Wushan Loess" is mainly imported from the north and is homologous to the loess of Loess Plateau. Therefore,we believe that "Wushan Loess" is not formed by stockpiling dust from the drying up tributaries in Three Gorges area due to the glacial period,which is different from the research result of "Xiashu Loess" in the lower reaches of the Yangtze River in recent years.
As one of the most important elements of the loess in southern China,the provenance of "Wushan Loess" can provide crucial environmental information to deciphering valuable sedimentary record in the area. Based on previous studies,we have collected samples from "Wushan Loess" profile and carried out Sr-Nd isotope analysis,and compared with sediments synchronous to Loess Plateau and fluvial sediments with nearby provenance. The results show that the variation range of 87Sr/86Sr of "Wushan Loess" is 0.717 411-0.719 163 with an average value of 0.717 998,which is almost identical with the 87Sr/86Sr values of Loess Plateau during the last glacial period (variation range is 0.718 235 to 0.719 673,average is 0.718 623).The value of εNd(0) of "Wushan Loess" loess ranges from -10.1 to -11.7 with an average value of -11.4,which is quite different from the value of εNd(0) (-5.9 to -7.2) of modern floodplain sediments in the upper reaches of the Yangtze River,is close to that of Loess Plateau (-9.2 to -11.3). Our research shows that the dust of "Wushan Loess" is mainly imported from the north and is homologous to the loess of Loess Plateau. Therefore,we believe that "Wushan Loess" is not formed by stockpiling dust from the drying up tributaries in Three Gorges area due to the glacial period,which is different from the research result of "Xiashu Loess" in the lower reaches of the Yangtze River in recent years.
2020, 45(3): 968-979.
doi: 10.3799/dqkx.2019.292
Abstract:
Large inversion anticlines formed at the end of the Miocene are widely developed in Xihu Sag in the East China Sea,which have generally attributed to external forces,ignoring the influence of the internal structure of the sag. Based on the comprehensive interpretation and analysis of gravity and magnetic seismic data,this paper systematically sorts out the relationship between the distribution of inversion anticlines at the end of Miocene and the basement structure,and discusses the influence of basement structure difference on the development of inversion anticlines in Xihu Sag by combining with structural physical simulation experimental methods. The research results show that there is a clear correlation between the inversion anticline at the end of Miocene and the distribution of high magnetic igneous rock basement,and it shows South-North segments. The igneous rock basement in the northern part of the sag is distributed in the central sag-inversion zone,and the inversion anticline is mainly developed on the eastern edge of the igneous rock basement. The igneous rock basement in the southern part of the sag is distributed on the eastern and western edges,and the inversion anticline is mainly developed on the inner side of the distribution area of the igneous rock basement on the edge. Structural physical simulation results show that under the compression background,the compressive stress is released through the edge of rigid silica gel to control the formation of compression anticline folds. The results reflect the difference in compressive strength caused by different lithological basement and can significantly affect the strength distribution of inversion anticlines. Finally,this paper proposes that the change of regional tectonic stress caused by igneous rock basement with high magnetic and high compressive strength is the key to control the strength distribution of the inversion anticline at the end of Miocene.
Large inversion anticlines formed at the end of the Miocene are widely developed in Xihu Sag in the East China Sea,which have generally attributed to external forces,ignoring the influence of the internal structure of the sag. Based on the comprehensive interpretation and analysis of gravity and magnetic seismic data,this paper systematically sorts out the relationship between the distribution of inversion anticlines at the end of Miocene and the basement structure,and discusses the influence of basement structure difference on the development of inversion anticlines in Xihu Sag by combining with structural physical simulation experimental methods. The research results show that there is a clear correlation between the inversion anticline at the end of Miocene and the distribution of high magnetic igneous rock basement,and it shows South-North segments. The igneous rock basement in the northern part of the sag is distributed in the central sag-inversion zone,and the inversion anticline is mainly developed on the eastern edge of the igneous rock basement. The igneous rock basement in the southern part of the sag is distributed on the eastern and western edges,and the inversion anticline is mainly developed on the inner side of the distribution area of the igneous rock basement on the edge. Structural physical simulation results show that under the compression background,the compressive stress is released through the edge of rigid silica gel to control the formation of compression anticline folds. The results reflect the difference in compressive strength caused by different lithological basement and can significantly affect the strength distribution of inversion anticlines. Finally,this paper proposes that the change of regional tectonic stress caused by igneous rock basement with high magnetic and high compressive strength is the key to control the strength distribution of the inversion anticline at the end of Miocene.
2020, 45(3): 980-988.
doi: 10.3799/dqkx.2019.016
Abstract:
The oil and gas resources of the buried hills in the Bohai Bay Basin are abundant. The oil and gas exploration in the Paleozoic buried hills in the Huanghua Depression has made significant progress recently,but the accumulation period of the oil and gas reservoirs is still unclear.The systematic study on the hydrocarbon accumulation period of the Paleozoic oil and gas reservoirs in the Beidagang buried hill is carried out using comprehensive utilization of reservoir solid bitumen analysis method,fluid inclusion analysis method and microscopic temperature measurement technology,in combination with Raman spectroscopy and infrared spectrum analysis and other geochemical analysis methods. The results show that the study area has three kinds of reservoir bitumen,including carbonaceous bitumen,colloid-asphaltene bitumen and oily bitumen,which have undergone various secondary transformation processes such as biodegradation and oxidation. It is confirmed that there is oil and gas charge before the middle Early Jurassic according to structural evolution of the study area.Two hydrocarbon inclusions are developed in the study area. The first stage of the inclusions shows yellow-brown fluorescence,which is mainly distributed on the surface of quartz particles and calcite veins. The homogenization temperature peak range is 75-80 ℃. The second phase inclusions show yellow and blue-green fluorescence,which are distributed in the fractures within the quartz grains,fractures through quartz grains and the calcite veins. The homogenization temperature peak ranges of the two are 85-90 ℃ and 95-100 ℃ respectively.Combining with the hydrocarbon generation history of source rocks,there are two stages of hydrocarbon accumulation in Paleozoic reservoirs,which are Middle Triassic (235-223 Ma) and Neogene-Quaternary (22-0 Ma),and the second period is the major stage.
The oil and gas resources of the buried hills in the Bohai Bay Basin are abundant. The oil and gas exploration in the Paleozoic buried hills in the Huanghua Depression has made significant progress recently,but the accumulation period of the oil and gas reservoirs is still unclear.The systematic study on the hydrocarbon accumulation period of the Paleozoic oil and gas reservoirs in the Beidagang buried hill is carried out using comprehensive utilization of reservoir solid bitumen analysis method,fluid inclusion analysis method and microscopic temperature measurement technology,in combination with Raman spectroscopy and infrared spectrum analysis and other geochemical analysis methods. The results show that the study area has three kinds of reservoir bitumen,including carbonaceous bitumen,colloid-asphaltene bitumen and oily bitumen,which have undergone various secondary transformation processes such as biodegradation and oxidation. It is confirmed that there is oil and gas charge before the middle Early Jurassic according to structural evolution of the study area.Two hydrocarbon inclusions are developed in the study area. The first stage of the inclusions shows yellow-brown fluorescence,which is mainly distributed on the surface of quartz particles and calcite veins. The homogenization temperature peak range is 75-80 ℃. The second phase inclusions show yellow and blue-green fluorescence,which are distributed in the fractures within the quartz grains,fractures through quartz grains and the calcite veins. The homogenization temperature peak ranges of the two are 85-90 ℃ and 95-100 ℃ respectively.Combining with the hydrocarbon generation history of source rocks,there are two stages of hydrocarbon accumulation in Paleozoic reservoirs,which are Middle Triassic (235-223 Ma) and Neogene-Quaternary (22-0 Ma),and the second period is the major stage.
2020, 45(3): 989-997.
doi: 10.3799/dqkx.2019.069
Abstract:
The distinctive types of slope breaks of Wenchang Sag inside the Pearl River Mouth Basin are formed by a series of tectonic evolution and complex structural deformation. Based on the theory from Tectonic Sedimentology and Sequence Stratigraphy,we identified four main terrestrial slope breaks types and analyzed the sand control effect caused by these types,with the combination of drilling data and three-dimensional seismic data. Fault slope break zones are distributed in the steep slope of South Wenchang Sag. This type of breaks can be further divided into mono-faulted,multistage,and brush basin-marginal fault slope breaks. The sand body distribution of fan delta,slump fan,sublacustrine fan are controlled by these breaks. Flexure,depositional and erosional slope breaks distributed inside the gentle slope of North Wenchang Sag. The sand body distribution of incise channel,delta and small sublacustrine fan are controlled by them. Besides,the small scale faults developed in the glacis slope breaks could adjust and transform the filling direction of sediments and the distribution of sedimentary systems. In addition,those sand bodies controlled by slope breaks are favorable positions for forming non-structural trap. In a word,they have huge potential for exploration.
The distinctive types of slope breaks of Wenchang Sag inside the Pearl River Mouth Basin are formed by a series of tectonic evolution and complex structural deformation. Based on the theory from Tectonic Sedimentology and Sequence Stratigraphy,we identified four main terrestrial slope breaks types and analyzed the sand control effect caused by these types,with the combination of drilling data and three-dimensional seismic data. Fault slope break zones are distributed in the steep slope of South Wenchang Sag. This type of breaks can be further divided into mono-faulted,multistage,and brush basin-marginal fault slope breaks. The sand body distribution of fan delta,slump fan,sublacustrine fan are controlled by these breaks. Flexure,depositional and erosional slope breaks distributed inside the gentle slope of North Wenchang Sag. The sand body distribution of incise channel,delta and small sublacustrine fan are controlled by them. Besides,the small scale faults developed in the glacis slope breaks could adjust and transform the filling direction of sediments and the distribution of sedimentary systems. In addition,those sand bodies controlled by slope breaks are favorable positions for forming non-structural trap. In a word,they have huge potential for exploration.
2020, 45(3): 998-1012.
doi: 10.3799/dqkx.2019.293
Abstract:
This study focuses on the distribution of high-quality carbonate reservoirs and new exploration areas in the Dengying Formation (Sinian) on the eastern side of Mianyang-Changning intracratonic sag. Using drilling, logging and seismic data in the Gaoshiti-Moxi, we identify the large early platform margin of Dengying Formation and characterize its internal configuration, based on the theories including the transgression-regression cycle analysis, the layer flattening, the seismic line drawing, the impression method paleogeomorphology, and quality reservoir prediction. It is found that, on the SE-NW seismic profile in the east of Mianyang-Changning intracratonic sag, there are several progradation reflections identified for the first time within the third sequence (SQ3) of Dengying Formation, which prograded from southeast to northwest with a S-shaped, mound or short axis in cross section. At the top of these progradation reflections, there are an obvious slope break point and a series of onlap points of SQ4 transgressive system tract. The thickness of SQ3 from the slope break point to the northwest is sharply thinned and wedge-shaped. The results show that there is a large early platform margin belt about 270 km long in the carbonate platform in the east of Mianyang-Changning extensional trough, which starts from the Gaoshiti, extends northeastward to the middle of Longgang area through Moxi, Longnvsi, Nanchong and Peng'an areas. The discovery of this large platform marginal zone will provide a new area for the oil and gas exploration of the Dengying Formation in the study area, and it will no longer be limited to the vicinity of Mianyang-Changning intracratonic sag.
This study focuses on the distribution of high-quality carbonate reservoirs and new exploration areas in the Dengying Formation (Sinian) on the eastern side of Mianyang-Changning intracratonic sag. Using drilling, logging and seismic data in the Gaoshiti-Moxi, we identify the large early platform margin of Dengying Formation and characterize its internal configuration, based on the theories including the transgression-regression cycle analysis, the layer flattening, the seismic line drawing, the impression method paleogeomorphology, and quality reservoir prediction. It is found that, on the SE-NW seismic profile in the east of Mianyang-Changning intracratonic sag, there are several progradation reflections identified for the first time within the third sequence (SQ3) of Dengying Formation, which prograded from southeast to northwest with a S-shaped, mound or short axis in cross section. At the top of these progradation reflections, there are an obvious slope break point and a series of onlap points of SQ4 transgressive system tract. The thickness of SQ3 from the slope break point to the northwest is sharply thinned and wedge-shaped. The results show that there is a large early platform margin belt about 270 km long in the carbonate platform in the east of Mianyang-Changning extensional trough, which starts from the Gaoshiti, extends northeastward to the middle of Longgang area through Moxi, Longnvsi, Nanchong and Peng'an areas. The discovery of this large platform marginal zone will provide a new area for the oil and gas exploration of the Dengying Formation in the study area, and it will no longer be limited to the vicinity of Mianyang-Changning intracratonic sag.
2020, 45(3): 1013-1026.
doi: 10.3799/dqkx.2019.046
Abstract:
Medium-light oil was discovered in the Ordovician of Well YQX1, which is located in heavy oil exploration area, North Shaya Uplift in the Tarim Basin. In order to figure out the origin of medium-light oil, 52 crude oil samples from Shaya Uplift have been employed to test diamondoid compounds, and diagenetic observation and fluid inclusions analyses on 131 core samples have been made. Geochemical characteristics of trapped oil in petroleum inclusions have been analyzed by GC-MS method. Hydrocarbon charging periods have been obtained by the method of homogenization temperature (Th) of fluid inclusion projecting on burial history diagram with thermal curve. Combining faults characteristics and caprock distribution of study area, the pattern of hydrocarbon accumulation has been rebuilt. It is found that biodegradation of crude oil is common and mixing of heavy oil and light oil has occurred in some parts of the study area. Besides, three events of hydrocarbon accumulation occurred in the Ordovician of Yuqixi area, in the Late Caledonian (452.5-420.5 Ma), the Yanshanian (150.2-100.6 Ma), and the Late Himalaya (20.1-2.1 Ma), respectively. Biodegradation of crude oil resulted from tectonic uplift, which was followed by vertical migration of light oil along NW, NNE strike-slip faults in the Cambrian and Ordovician, resulting in the formation of oil mixing and current medium-light oil pools.
Medium-light oil was discovered in the Ordovician of Well YQX1, which is located in heavy oil exploration area, North Shaya Uplift in the Tarim Basin. In order to figure out the origin of medium-light oil, 52 crude oil samples from Shaya Uplift have been employed to test diamondoid compounds, and diagenetic observation and fluid inclusions analyses on 131 core samples have been made. Geochemical characteristics of trapped oil in petroleum inclusions have been analyzed by GC-MS method. Hydrocarbon charging periods have been obtained by the method of homogenization temperature (Th) of fluid inclusion projecting on burial history diagram with thermal curve. Combining faults characteristics and caprock distribution of study area, the pattern of hydrocarbon accumulation has been rebuilt. It is found that biodegradation of crude oil is common and mixing of heavy oil and light oil has occurred in some parts of the study area. Besides, three events of hydrocarbon accumulation occurred in the Ordovician of Yuqixi area, in the Late Caledonian (452.5-420.5 Ma), the Yanshanian (150.2-100.6 Ma), and the Late Himalaya (20.1-2.1 Ma), respectively. Biodegradation of crude oil resulted from tectonic uplift, which was followed by vertical migration of light oil along NW, NNE strike-slip faults in the Cambrian and Ordovician, resulting in the formation of oil mixing and current medium-light oil pools.
2020, 45(3): 1027-1040.
doi: 10.3799/dqkx.2019.088
Abstract:
The problem of aquifer destruction persists in the whole life cycle of coal mine, which has long-term effect on ecology and social economy. In order to analyze the risk of aquifer destruction in underground mining coal, this paper proposes a technical framework of risk assessment and management of aquifer destruction on the basis of analyses of the hydrogeologic structure and aquifer destruction mode of main coal mines of North China. The technical framework was applied to the risk analyses of the aquifer destruction of Hongshan mine, Zibo City, using the monitoring data. It is found that: (i) The aquifer destruction of mining coal includes three categories: aquifer structure's destruction, change of groundwater flow field, and groundwater contaminants. In Hongshan mine, Ordovician limestone water has a high probability of destruction, and hazard areas with high, moderate and low risk are 20.61 km2, 22.39 km2 and 19.26 km2 respectively. (ii) Vulnerabilities of society, economy and ecology depend on three indexes of damage, fragility and resilience. The social economy of Hongshan mine depends highly on Ordovician limestone water and has high vulnerability for limestone aquifer destruction. (iii) The risk of aquifer destruction is from available groundwater resources reduction, ecological degradation and social-economic recession. It is suggested that Hongshan mine closure increased the aquifer destruction risk.
The problem of aquifer destruction persists in the whole life cycle of coal mine, which has long-term effect on ecology and social economy. In order to analyze the risk of aquifer destruction in underground mining coal, this paper proposes a technical framework of risk assessment and management of aquifer destruction on the basis of analyses of the hydrogeologic structure and aquifer destruction mode of main coal mines of North China. The technical framework was applied to the risk analyses of the aquifer destruction of Hongshan mine, Zibo City, using the monitoring data. It is found that: (i) The aquifer destruction of mining coal includes three categories: aquifer structure's destruction, change of groundwater flow field, and groundwater contaminants. In Hongshan mine, Ordovician limestone water has a high probability of destruction, and hazard areas with high, moderate and low risk are 20.61 km2, 22.39 km2 and 19.26 km2 respectively. (ii) Vulnerabilities of society, economy and ecology depend on three indexes of damage, fragility and resilience. The social economy of Hongshan mine depends highly on Ordovician limestone water and has high vulnerability for limestone aquifer destruction. (iii) The risk of aquifer destruction is from available groundwater resources reduction, ecological degradation and social-economic recession. It is suggested that Hongshan mine closure increased the aquifer destruction risk.
2020, 45(3): 1041-1050.
doi: 10.3799/dqkx.2019.953
Abstract:
As one of the four granaries in China, Jianghan Plain has approximately 690 thousand hectares of seleniferous soil, most of which are cold waterlogged paddy field. How to utilize the seleniferous cold waterlogged paddy field to cultivate selenium-enriched rice is a major practical problem that needs to be solved urgently. In order to find the best utilization mode of seleniferous cold waterlogged paddy field in Jianghan Plain, this study conducted field experiments using three different utilization modes, namely drainage mode, selenium fertilizer amendment mode, drainage and selenium fertilizer amendment mode. The results show that under the drainage mode both bioavailable Se content in soil and Se content in rice grain increased by 20.6% and 8.3% respectively, compared to those in control samples, because drainage decreased the groundwater table level and improved the aeration and redox potential in soil, thus accelerated the organic-bound selenium transform to bioavailable selenium in soil, and promoted the uptake of selenium by rice. Under the selenium fertilizer amendment mode, the bioavailable selenium content in soil increased by 41.7% after applying selenium fertilizer than that in control without selenium fertilizer, which greatly promoted the uptake of selenium by rice, and the selenium contents in rice root, straw and grain increased by 79.4% 37.1% and 25.0%, respectively. Under the drainage and selenium fertilizer amendment mode, the bioavailable selenium content in soil and selenium contents in rice root, straw, and grain increased by 50.0%, 41.8%, 46.1% and 47.9% respectively than those in the control samples. This study demonstrates that all the three utilization modes mentioned above can increase the bioavailable selenium content in the cold waterlogged paddy soil, which is beneficial to the uptake of selenium from soil by rice, and can significantly increase the content of selenium in rice grain. Overall, the drainage and selenium fertilizer amendment is the best mode for the utilization of seleniferous cold waterlogged paddy soil.
As one of the four granaries in China, Jianghan Plain has approximately 690 thousand hectares of seleniferous soil, most of which are cold waterlogged paddy field. How to utilize the seleniferous cold waterlogged paddy field to cultivate selenium-enriched rice is a major practical problem that needs to be solved urgently. In order to find the best utilization mode of seleniferous cold waterlogged paddy field in Jianghan Plain, this study conducted field experiments using three different utilization modes, namely drainage mode, selenium fertilizer amendment mode, drainage and selenium fertilizer amendment mode. The results show that under the drainage mode both bioavailable Se content in soil and Se content in rice grain increased by 20.6% and 8.3% respectively, compared to those in control samples, because drainage decreased the groundwater table level and improved the aeration and redox potential in soil, thus accelerated the organic-bound selenium transform to bioavailable selenium in soil, and promoted the uptake of selenium by rice. Under the selenium fertilizer amendment mode, the bioavailable selenium content in soil increased by 41.7% after applying selenium fertilizer than that in control without selenium fertilizer, which greatly promoted the uptake of selenium by rice, and the selenium contents in rice root, straw and grain increased by 79.4% 37.1% and 25.0%, respectively. Under the drainage and selenium fertilizer amendment mode, the bioavailable selenium content in soil and selenium contents in rice root, straw, and grain increased by 50.0%, 41.8%, 46.1% and 47.9% respectively than those in the control samples. This study demonstrates that all the three utilization modes mentioned above can increase the bioavailable selenium content in the cold waterlogged paddy soil, which is beneficial to the uptake of selenium from soil by rice, and can significantly increase the content of selenium in rice grain. Overall, the drainage and selenium fertilizer amendment is the best mode for the utilization of seleniferous cold waterlogged paddy soil.
2020, 45(3): 1051-1060.
doi: 10.3799/dqkx.2019.089
Abstract:
The phreatic evaporation is the main discharge way of groundwater in arid inland basins,but its quantitative evaluation has great uncertainty,which leads to the difficulty of water balance analysis and water resources evaluation. In the plain area of the Manas River Basin in Xinjiang,saturated sodium bromide was applied at different sites in different land use types as a tracer in May 2017, and soil samples were collected in August 2017 and August 2018 for measuring bromide concentration. The evaporation rate of the phreatic water is determined based on the vertical migration of the bromide peaks. The vertical profiles of bromide ion concentration profiles show mainly a single peak moved upward. According to the upward moving distance of the peak,the annual average phreatic evaporation in the non-desert area is calculated as 33.59 mm. The evaporations of different land use types from strong to weak were cotton field,uncultivated land,forest and desert,and the annual average evaporations were 41.71 mm,34.01 mm,11.28 mm,8.58 mm,respectively. The results of bromide ion tracing method for evaluating the evaporation of phreatic water are consistent with the relevant literature. The phreatic evaporation rates are related to the land use type,the lithology of the aeration zone,the volumetric water content of the soil and the phreatic depth. The higher the clay content of the rock formation is,the higher the water content is,the closer to the low-lying area of the fine soil plain,the stronger phreatic evaporation is.
The phreatic evaporation is the main discharge way of groundwater in arid inland basins,but its quantitative evaluation has great uncertainty,which leads to the difficulty of water balance analysis and water resources evaluation. In the plain area of the Manas River Basin in Xinjiang,saturated sodium bromide was applied at different sites in different land use types as a tracer in May 2017, and soil samples were collected in August 2017 and August 2018 for measuring bromide concentration. The evaporation rate of the phreatic water is determined based on the vertical migration of the bromide peaks. The vertical profiles of bromide ion concentration profiles show mainly a single peak moved upward. According to the upward moving distance of the peak,the annual average phreatic evaporation in the non-desert area is calculated as 33.59 mm. The evaporations of different land use types from strong to weak were cotton field,uncultivated land,forest and desert,and the annual average evaporations were 41.71 mm,34.01 mm,11.28 mm,8.58 mm,respectively. The results of bromide ion tracing method for evaluating the evaporation of phreatic water are consistent with the relevant literature. The phreatic evaporation rates are related to the land use type,the lithology of the aeration zone,the volumetric water content of the soil and the phreatic depth. The higher the clay content of the rock formation is,the higher the water content is,the closer to the low-lying area of the fine soil plain,the stronger phreatic evaporation is.
2020, 45(3): 1071-1081.
doi: 10.3799/dqkx.2019.067
Abstract:
As a traditional industry in the Horqin area of Tongliao City,agriculture plays a pivotal role in the development of economy. Understanding the structure and function of soil microbial communities and their influencing factors is of great significance for crop planting and remediation of contaminated land. In this study,microbial community and function composition were investigated in a total of 71 soil samples collected from the Horqin area of Tongliao City with an integrated approach including 16S rRNA gene-based Illumina Miseq high-throughput sequencing technology and FAPROTAX.1.1 functional prediction platform,followed by statistical analysis with the use of R software package. The results show that the microbial communities in the studied soils were mainly composed of Proteobacteria (19.77%),Thaumarchaeota (17.85%),Acidobacteria (17.14%),Actinobacteria (15.58%). The functional prediction indicates that a large portion of the microbial communities in the studied soils were involved in nitrogen cycling,among which aerobic ammonia oxidation function predominated. Variation partition analysis (VPA) indicates that environmental factors accounted much more for the shaping of microbial community structure in interpretable range than spatial factors. Mantel test shows that the microbial communities in the studied soils were significantly (p < 0.05) correlated with soil pH,electrical conductivity (EC),total nitrogen (TN),ratio of carbon to nitrogen,and concentration of Mg,Na and Sr elements. It is concluded that pH,EC and Sr element concentrations were important environmental factors affecting the microbial community composition,function and diversity in the soils of the Horqin area of Tongliao City.
As a traditional industry in the Horqin area of Tongliao City,agriculture plays a pivotal role in the development of economy. Understanding the structure and function of soil microbial communities and their influencing factors is of great significance for crop planting and remediation of contaminated land. In this study,microbial community and function composition were investigated in a total of 71 soil samples collected from the Horqin area of Tongliao City with an integrated approach including 16S rRNA gene-based Illumina Miseq high-throughput sequencing technology and FAPROTAX.1.1 functional prediction platform,followed by statistical analysis with the use of R software package. The results show that the microbial communities in the studied soils were mainly composed of Proteobacteria (19.77%),Thaumarchaeota (17.85%),Acidobacteria (17.14%),Actinobacteria (15.58%). The functional prediction indicates that a large portion of the microbial communities in the studied soils were involved in nitrogen cycling,among which aerobic ammonia oxidation function predominated. Variation partition analysis (VPA) indicates that environmental factors accounted much more for the shaping of microbial community structure in interpretable range than spatial factors. Mantel test shows that the microbial communities in the studied soils were significantly (p < 0.05) correlated with soil pH,electrical conductivity (EC),total nitrogen (TN),ratio of carbon to nitrogen,and concentration of Mg,Na and Sr elements. It is concluded that pH,EC and Sr element concentrations were important environmental factors affecting the microbial community composition,function and diversity in the soils of the Horqin area of Tongliao City.
2020, 45(3): 1082-1092.
doi: 10.3799/dqkx.2019.289
Abstract:
Although the methane flux characteristics and the composition of soil microbial community in the Dajiuhu peatland in Shennongjia have been studied to some extent, there are few studies on the relationship and impact of microbial community and methane flux. Using eddy covariance method and high throughput sequencing technology, methane flux and structure of microorganism were investigated at the Dajiuhu peatland from March 2016 to February 2017. The results show that the Dajiuhu peatland was the source of CH4 during the study period, with an annual total discharge of 5 566.27 mg·m-2 and a daily average emission rate of 10.96 nmol·m-2·s-1. The average fluxes of the four seasons were 12.06, 22.47, 3.02, 2.92 nmol·m-2·s-1, respectively. The dominant bacterium in the study area were Crenarchaecta (54.6%), Euryarchaeota (18.9%), and Acidobacteria (12.6%). Univariate analysis was performed on the Shannon index for different season samples with a p value of 0.000 127. The results showed that the change of the monthly methane emission flux during this year had clearly inverted " U" type curve, and CH4 emission rate in summer was the highest which was the lowest in winter. There were significant differences in soil microbial composition between different seasons. There was a strong positive correlation between the microbial community composition and the methane emission flux during summer and a strong negative correlation during winter. Abundance of Parcubacteria showed a significant positive correlation with CH4 flux, while abundance of Crenarchaecta showed a significant negative correlation with CH4 flux.
Although the methane flux characteristics and the composition of soil microbial community in the Dajiuhu peatland in Shennongjia have been studied to some extent, there are few studies on the relationship and impact of microbial community and methane flux. Using eddy covariance method and high throughput sequencing technology, methane flux and structure of microorganism were investigated at the Dajiuhu peatland from March 2016 to February 2017. The results show that the Dajiuhu peatland was the source of CH4 during the study period, with an annual total discharge of 5 566.27 mg·m-2 and a daily average emission rate of 10.96 nmol·m-2·s-1. The average fluxes of the four seasons were 12.06, 22.47, 3.02, 2.92 nmol·m-2·s-1, respectively. The dominant bacterium in the study area were Crenarchaecta (54.6%), Euryarchaeota (18.9%), and Acidobacteria (12.6%). Univariate analysis was performed on the Shannon index for different season samples with a p value of 0.000 127. The results showed that the change of the monthly methane emission flux during this year had clearly inverted " U" type curve, and CH4 emission rate in summer was the highest which was the lowest in winter. There were significant differences in soil microbial composition between different seasons. There was a strong positive correlation between the microbial community composition and the methane emission flux during summer and a strong negative correlation during winter. Abundance of Parcubacteria showed a significant positive correlation with CH4 flux, while abundance of Crenarchaecta showed a significant negative correlation with CH4 flux.
2020, 45(3): 1061-1070.
doi: 10.3799/dqkx.2019.060
Abstract:
There are few studies on the source identification of nitrate in the natural rivers in karst area, and even fewer on the influence of the anti-seasonal arid climate on the nitrate transportation. In this paper, δ15N and δ18O isotopic tracing method is used to analyze the source of nitrate in surface water and groundwater of Quanshui River, a branch of Hangjiang River and to determine the biological and chemical transformation process of nitrate. The contribution rate of each pollution terminal element was determined quantitatively by using the model of Stable Isotope Analysis in R (SIAR). The results show that soil organic nitrogen, sewage manure, fertilizer and atmospheric subsidence contributed 31.4%, 20.0%, 29.6% and 19.0% respectively to the nitrate source of groundwater, and the proportion of nitrate source to surface water was 32.0%, 30.0%, 25.0% and 13.0%. The contribution of sewage manure to surface water nitrate is significantly higher than that of groundwater. Due to the large water body, the water in the reservoir has strong self-purification ability and is almost unaffected by sewage manure (only 9.0%).The contribution of soil organic nitrogen, atmospheric subsidence and fertilizer in the nitrate soil of the reservoir was 43.0%, 11.0% and 37.0%, respectively. In dry season, groundwater is mainly recharged slowly by groundwater. Because groundwater is affected by soil in vadose zone, soil organic nitrogen is the main source of nitrate in the river. The downstream of the river is more susceptible to human activities, and the contribution of domestic sewage and chemical fertilizer to nitrate in rivers increases.
There are few studies on the source identification of nitrate in the natural rivers in karst area, and even fewer on the influence of the anti-seasonal arid climate on the nitrate transportation. In this paper, δ15N and δ18O isotopic tracing method is used to analyze the source of nitrate in surface water and groundwater of Quanshui River, a branch of Hangjiang River and to determine the biological and chemical transformation process of nitrate. The contribution rate of each pollution terminal element was determined quantitatively by using the model of Stable Isotope Analysis in R (SIAR). The results show that soil organic nitrogen, sewage manure, fertilizer and atmospheric subsidence contributed 31.4%, 20.0%, 29.6% and 19.0% respectively to the nitrate source of groundwater, and the proportion of nitrate source to surface water was 32.0%, 30.0%, 25.0% and 13.0%. The contribution of sewage manure to surface water nitrate is significantly higher than that of groundwater. Due to the large water body, the water in the reservoir has strong self-purification ability and is almost unaffected by sewage manure (only 9.0%).The contribution of soil organic nitrogen, atmospheric subsidence and fertilizer in the nitrate soil of the reservoir was 43.0%, 11.0% and 37.0%, respectively. In dry season, groundwater is mainly recharged slowly by groundwater. Because groundwater is affected by soil in vadose zone, soil organic nitrogen is the main source of nitrate in the river. The downstream of the river is more susceptible to human activities, and the contribution of domestic sewage and chemical fertilizer to nitrate in rivers increases.
